Feel Better, Live More with Dr Rangan Chatterjee - The New Science Of The Body Clock: How To Boost Your Immune System, Reclaim Your Energy & Improve Your Mental Health with Dr Kristen Holmes #479

Episode Date: September 24, 2024

In our hyper-connected modern world, where we have access to artificial light and food around-the-clock, we've drifted far from our body’s natural rhythms. But what if reconnecting with these internal clocks could be the key to unlocking better health, more energy and even a longer life? My guest this week is Kristen Holmes, who is Global Head of Human Performance and Principal Scientist at WHOOP, a Science Advisor to Levels Health and Arena Labs, and a member of the Tactical Leadership Board of Sports Innovation Lab. In this conversation, we explore the world of circadian biology and how aligning our daily habits with our natural rhythms can transform our health. Kristen explains the far-reaching consequences of a disrupted circadian rhythm, from metabolic disorders and increased ageing to mental health challenges and lower immune function. We discuss the critical importance of consistent sleep/wake times, even on weekends, and how this simple change can dramatically improve our psychological and physiological functioning. Kristen shares her personal experience of how aligning her circadian rhythms has boosted her productivity, focus, and overall health - she hasn't been ill for over eight years. Throughout our conversation, we explore strategies for harmonising our circadian rhythms within the context of modern life. We cover the importance of morning light exposure, the ideal timing for meals, and how to manage factors like alcohol and caffeine consumption. Kristen also provides valuable advice for shift workers on maintaining healthy rhythms despite irregular schedules. This conversation really is packed with actionable insights and I hope that it leaves you feeling empowered to take control of your daily rhythms and experience the transformative effects on your health that can help you tune into your body's natural rhythms and optimise your health.  Support the podcast and enjoy Ad-Free episodes. Try FREE for 7 days on Apple Podcasts https://apple.co/feelbetterlivemore. For other podcast platforms go to https://fblm.supercast.com. Thanks to our sponsors: https://airbnb.co.uk/host https://thriva.co Save 30% off your first subscription order & receive a free six pack of Ketone-IQ with KETONE.com/LIVEMORE https://drinkag1.com/livemore   Show notes https://drchatterjee.com/479   DISCLAIMER: The content in the podcast and on this webpage is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your doctor or qualified healthcare provider. Never disregard professional medical advice or delay in seeking it because of something you have heard on the podcast or on my website.

There is not a single mental health disorder that circadian rhythm disruption doesn't touch. I've just seen it over and over and over again in the data. The one behavior that bubbles up and is predictive of physiological and psychological functioning is sleep-wake timing. The more stable it is, the higher levels of psychological functioning, and the stronger the physiological markers. Hey guys, how you doing? Hope you're having a good week so far.

My name is Dr. Rangan Chatterjee, and this is my podcast, Feel Better, Live More. In our hyper-connected modern world, where we're exposed to artificial light at all hours and have access to food around the clock, one of the consequences is that we've drifted far away from our body's natural rhythms. But could it be that reconnecting with these rhythms is one of the keys to unlocking better health, more energy, and even a longer life? This week, my guest is Kristen Holmes. She's the global head of human performance and principal scientist at Whoop, a science advisor to Levels Health and Arena Labs, and a member of the tactical leadership board of Sports Innovation Lab. In our conversation,

we explore the world of circadian biology and how aligning our daily habits with our natural rhythms can be absolutely transformative for our health. Kristen explains the far-reaching consequences of a disrupted circadian rhythm, from metabolic disorders and increased aging, to mental health challenges and lower immune function. She also explains the critical importance of consistent sleep-wait times, the body's need for morning light exposure, the ideal timing for meals, and how to manage factors like alcohol and caffeine. We also explore what shift workers can do to maintain healthy rhythms despite irregular schedules. And Kristen also shares her own personal experiences of how aligning her

circadian rhythms has massively boosted her productivity, focus and overall health. In fact, she shares that she hasn't been ill in over eight years. I thoroughly enjoyed my conversation with Kristen. She's someone who is incredibly knowledgeable and super passionate about improving the health of others. This episode is full of actionable insights and my hope is that it leaves you feeling empowered to take control of your daily rhythms and experience the transformative effects on your health. health. I want to talk today about how our daily habits, things like alcohol, caffeine, screen time, affect our circadian biology and our health. But before we do that, I'd love you to explain what is a circadian rhythm and what are the consequences of us having our circadian rhythms disrupted? Yeah, so circadian rhythms very simply are the physical, mental, and behavioral processes

that are happening over a 24-hour cycle. And the consequences of desynchronized circadian rhythms. And we know this, there's lots and lots of evidence in the literature that the consequences of desynchronized circadian rhythms, that is basically bypassing our natural internal preferences, right? Which we want to try to match our natural internal preferences with the light-dark cycle. That's the most prominent cue to entrain our circadian rhythms and to create this circadian alignment. So for example, when we are viewing light at a phase of the natural light-dark cycle, that puts enormous stress on our body. So we know this as viewing light at night, for example, after the sun sets, right? Or not getting enough light in the morning as the sun

is coming up. So this basically confuses our system in that our internal clocks become disorganized or don't quite know what to do. And this creates misalignment. Now there are other behaviors that help and train our circadian rhythm. So the timing of our meals, okay, so when we're eating our food, when we are active and social, when we go to bed, when we wake up, we want to try to align these behaviors with the natural light-dark cycle. So when we're supposed to be active and eating and sleeping, we want to try to do that in a way that's aligned with these natural environmental cues. And when our circadian rhythms are disrupted, as they are for so many people these days,

just shed a light on some of those consequences so that everyone listening can really understand that this is actually very, very serious. It's not just about feeling good in the moment. Of course, it will help you feel good and give you more energy and more focus. But there are some quite serious long-term consequences, aren't there, when we have misaligned circadian rhythms there there are yeah and uh you know and this is really this is the subject of my phd my dissertation is on circadian alignment um and really trying to unpack you know what are exactly the behaviors that are going to influence our ability to create this alignment and and indeed what are the consequences. So we know that there's an increased risk of metabolic disorders and metabolic dysfunction. We know that

there is not a single mental health disorder that circadian rhythm disruption doesn't touch. So if we are chronically misaligned, our internal system becomes very confused. And this cellular miscommunication is really, I think, the basis of most disease and frankly, aging. And so it is serious. I'm inside sleep and recovery and training. And I do a lot of research across these various areas. And it's very, very obvious to me that circadian rhythms and circadian alignment is the foundation of your house. And when that is not firing on whole cylinders,

anything we attempt to layer on top of that is really just inefficiency, layering inefficiency on top of inefficiency. So, you know, any nutrition protocols that we're trying to deploy or any, you know, exercise, like in order to really capitalize on these other things that we're doing, circadian, the timing of when we're viewing light, when we're restricting light, when we are eating, when we are sleeping, when we're waking up, you know, and when we're active, the timing of those things is absolutely central to our overall health and longevity. Yeah, no, I love the way you put that. I've been a medical doctor now for 23 years. And, you know, one thing I've realized over the past, I would say at least a decade is that if you haven't got the basic foundational pillars of health dialed in as well as you can, you simply don't know how many of your symptoms are just a consequence of that. So as doctors, we often will treat your symptoms and say, you have this condition. And you may do,

but sometimes that's just a natural consequence of the fact that you are living in some sort of circadian misalignment. So of course, your mood is low. Of course, your brain function isn't where you want it to be. Of course, you're putting on weight, etc, etc. So for many years, as much as I can, and with shift work as it can be more challenging, and we'll talk about that for sure, I'm always focusing on, for me, what I call these four pillars of health, food, movement, sleep, and relaxation. Yeah, I think that's beautifully said, of course. And I think, but where I think we, it's not that we don't go wrong, but I think people, we think about sleep, for example, right? Sleep doesn't have a circadian rhythm, but it's an output of the circadian clock, right? So it's our daytime behaviors that dictate our ability to fall asleep and stay asleep and get that

beautiful restorative night's sleep, right? But we're not really coached on what are the behaviors that actually create this beautiful night's sleep, right? We're told to spend more time in bed. We're told to focus on our sleep. We might talk about our sleep hygiene, which is very sleep, right? We're told to spend more time in bed. We're told to focus on our sleep. We might talk about our sleep hygiene, which is very important, right? But unless our circadian rhythms are aligned, sleep is gonna be very difficult. And I think that's one of the biggest problems in modernity.

A lot of this is because we're living in a world where we have access to light 24 seven. We have access to light 24-7. We have access to food 24-7. And as a result, we're creating just a lot of stress on our system. And this manifests, of course, in things like our alertness and our ability to attend to the things that matter to us during the day. But it really, really impacts our sleep at night. So as a result, we are really trying to push water uphill,

I think, as it relates to many of the health goals that we have, because we're really not focused on the foundation. Yeah, it's really interesting there. You mentioned that we have this 24-7 access now to light and food. And there's quite a beautiful contrast there between constant access and the rhythmical nature of our bodies. We're not meant to have that constancy of access to these things. We're meant to eat at certain times. We're meant to see light at certain times. And until very recently, that is what we would have done. And it's this kind of mismatch, isn't there? And it's, you know, I've been really excited about talking to you because you talk about physiology and psychology. And I'm also very

passionate about those two things. I don't think you can look at physiology and how that impacts people without also looking at psychology. And so something's just come to me, right? I wrote this book on happiness. And one of the components of happiness to me is alignment when your internal values and your external actions start to align more and more. And the way you're talking about our circadian rhythms is also about that internal and that external starting to align right yeah so can you just speak to that a little bit because i think it's really really interesting i love that you highlighted that um yeah i mean i'm a psychophysiologist so i i study the interactions between the mind and the body and and there's no

question right when when our, when our behaviors are not a reflection of the things that we say we care about, the things that we say we value, right? That creates this internal mismatch, this internal dissonance, right? That manifests in, in our, in our life and all sorts of ways that are really unproductive and maladaptive, right? So I think there is, there's this psychological kind of alignment, right, where we, you know, are able to think clearly about our purpose and we're able to practice being this person that we say we want to be in the world. Right. Which is, you know, our identity and and and live our values. And that's where we when we have all the really strong internal alignment. you know, really strong internal alignment. But, you know, if we are misaligned with these natural rhythms in the world, that is going to have a profound impact on our physiology, which is going to then in turn impact our mindset. It's going to impact our, you know, our motivation and our

energy production, right? For the things that we care about. So there's this incredible, you know, synergy that's happening between our mind and body all the time that's dictated by, you know, these internal rhythms, right? And creating these matches is really, I think, is kind of the bigger project here, right? And we want as many matches as possible. And I call these demand matches, right? Like we want our internal system, right? To be able to match the demands of our environment, right?

If I wanna feel sleepy when I wanna feel sleepy, I wanna feel alert when I wanna feel alert. I wanna be able to engage with the people I love in a way that feels good to me. You know, these are all kind of matches, right? But when our internal system is desynchronized, all of that becomes very, very friction filled, right? And very effortful, right? And that creates stress on our system. And that creates stress on our system. And that stress, of course, manifests in very real ways in terms of suppressing our immune system and creating constant activation with our HPA axis. These things are our autonomic nervous system, our sympathetic branch of our nervous system is chronically activated. This leads to disease

and aging, right? Yeah. Just so everyone who is listening really is understanding circadian biology, are you saying that everyone has an internal rhythm that has presumably been set in some way based upon their lifestyle and the way they're living. But ultimately, it is internal. And our job, therefore, is to have external behaviors in our life that match that internal rhythm as much as we possibly can. Yeah, that's exactly right. And I think where we go a little wrong is I think we believe that there lot of variability in terms of when you want to fall asleep and when I want to fall asleep, right? Based on kind of our endogenous preferences. And we know this from a lot of the literature and a lot of the research that's done

on hunter-gatherers, they're all going to wake a little bit up after sunrise and they're going to fall asleep a little bit after sunset, right? And indeed, when you put, you know, folks like us on a mountain with no electricity, we're all going to fall asleep within a half an hour of each other. So this notion that we have these really, you know, you know, varied chronotypes that span five hours, you know, that is just, I have, I can't, you know, when I interpret the literature, that's just not, that's just, I have, I can't, you know, when I interpret the literature, that's just not, that's not what I see, right? I see preferences and modernity has created in opportunity for us to, you know, be awake at 2 a.m. And it, but it doesn't mean just because

our system has adapted to it does not mean it's good for us. And I think that's the message as hard as I think it is for some folks to hear. That's kind of the message that I'm trying to get out there that, you know, we're really making choices, right? And we just have to own that choice, but we have to recognize that it is having a deleterious effect on our health, well-being, and our longevity, right? Mental, physical, emotional. Yeah, what you said about we're not as varied as we might think, I'm so happy to hear you say that. It's something I felt for many, many years now, based upon my clinical experience, which is that, you know, night owl, morning lark,

I know they talk about chronotypes. It just doesn't fit with what I've seen. I've had patients who swear to me that they're night owls, swear to me. I'd say, okay, look, this is the consequence at the moment of you being a night owl. You know, would you like to change that? A lot of them will say, okay, but is it possible? I said, okay, well, let's just try for a couple of weeks, you know, changing a few things. Light exposure in the evening being a huge one. Let's cut that out as much as we can. Let's get your dinner a bit earlier. Let's get you up early and get you outside, right? It is amazing how many night owls suddenly say, oh, I'm doing really well as a morning log. Now, I can't say that that's for

every single person, right? And I recognize that many sleep experts are saying that there are these chronotypes. But as you say, those studies where you go out camping or they go out to the mountains, when that happens and we're removed from artificial light, it all starts to sync up a bit better, doesn't it? It really does. And the evidence is just so darn clear to me, you know? And, you know, and I think we've created this notion of chronotype out of convenience, you know, really, because it just lets folks off the hook, you know?

It's, you know, I'm the night owl. I'm going to stay up and I'm going to watch Netflix until 1 a.m. But, you know, there's other evidence too, when we look at the timing of light exposure on mood and brain circuits, right? It's a beautiful paper. It was published in 2017. And basically, you know, what it said is that when we're viewing light between 11pm and

4am, your dopamine system, motivation, reward just doesn't work as well as it would have if you didn't view light between 11 p.m. and 4 a.m. And of course, if you're doing that, you know, once every now and again, not a big deal. But if you're chronically viewing light between 11 p.m. and 4 a.m., which is probably 70% of the world's population at this point, like a lot of folks are getting light to the eyes, which is, you know, confusing the control center of the brain saying we're supposed to be awake, which is then telling all of the clocks in the body that it's time to be awake at times when, again, they're not programmed to be awake.

They're not programmed to be, you know, firing, right? So again, this puts enormous stress on the system. So I think studies like that tell us, okay, there's something that we need to protect this timeframe. This is a time when we are not supposed to be active and awake, right? And so there's just more literature that's kind of mounting. And then, you know, all of the research that I've done over the course of the last four years for my thesis, the one behavior that bubbles up and is predictive of physiological and psychological functioning is sleep-wake timing. The more stable it is, the higher levels of psychological functioning, the more positive psychological functioning folks have, and the stronger the physiological markers. So we see relationships between

when we do these circadian behaviors, they impact our sleep-wake time, which then impacts our cardiorespiratory fitness and our parasympathetic activity. Wow. Like this, I'm about to submit this for peer review, so this is preliminary data. Jamie Zeitzer, a professor of asleep and circadian scientists, is on the paper as well.

So, really excited about it because this is the first time we've been able to show these really clear effects and they're super significant. So it was a pre-post quasi-experimental design. So it's just a super cool, huge data set. 338,000 folks were a part of the study. So, it's super cool. But it just reinforces everything that we're talking about that there is this, there are, I call it, there's four behaviors that are absolutely critical to creating, to help facilitating the sleep onset offset consistency, which we know is, again, I've just seen it over and over and over and over again in the data, God's view, sleep-wake timing is the most important behavioral experience we have, the most important behavior that we can adopt. Okay, we're going to go deep into that because it's absolutely fascinating. Before we do, I want to acknowledge there will be shift workers who are listening to

this who may be experiencing stress as they hear this. So we're definitely going to cover shift workers at some point. So I think it's really, really important that we acknowledge that there are people out there in society who do some of the most important jobs, who are living with circadian rhythm disruption. And I think that's something we really need to look at as societies. Is there a way to change that? What can we do to help them? So we'll come back to that. What you said about dopamine was really interesting. You mentioned that if we are regularly up looking at lights between 11pm and 4am, then our dopaminergic system doesn't work as well the following day. Now that has some quite profound implications.

Your motivation, your ability, your drive, your willingness to do the things that are required off you are going to do the things that are required of you are going to be affected by that. So you might think you have no focus. You can't resist temptation. You don't have passion. You may think that that's who you are. That's your personality, but maybe it ain't your personality. Maybe it's a consequence of the fact that you were viewing light at midnight. And then what also happens in my experience is that because we feel like that, we then consume more caffeine,

more sugar to get us through. We're consuming caffeine later in the day. And then we reinforce that belief that we're night owls because I'm not tired now till midnight. But hold on a minute. Maybe that's a knock-on consequence of the fact that you're consistently looking at lights at 11.30 PM. You're pushing back your melatonin secretion. Everything's off and you're then engaging in

behaviors that reinforce the idea that you're a night owl. And I don't, Chris, I was thinking about this this morning, right? We know that our circadian rhythm is not exactly 24 hours, right? It's slightly beyond that. And then we are setting it every day based on light and dark. So even if you accept that there are genetic chronotypes, the fact that we can change and respond to jet lag and time zones means that we can change it and our environmental inputs ultimately are what dictates it right so that I think it's empowering because it goes okay you know what can I do what choices can I make to harmonize my circadian rhythm in the context of my life as much as I can. Yeah, that was perfect. So well said and so validating for me to hear someone like you

say that because I just feel like people have really, really strong reactions to kind of fudging with their sleep-wake time and, you know, the precious chronotype. But I just think the evidence is really clear. And I've personally have been able to shift my circadian rhythm to an optimal kind of zone. And I have seen, you know, I obviously have been tracking data, my data for a really long time. Even prior to coming to WHOOP, I was a really early adopter in HRV. So heart variability is an incredible proxy for just our mental and physical health resilience. Incredible proxy for that. So when I was coaching, I was really deep into tracking these things.

So I've seen in my own experience, as a coach, I was very much a night owl. I was cutting film late into the night. I was sending coach, I was, you know, very much a night owl, you know, like I was cutting film, like late into the night, I was sending emails, I was doing all sorts of stuff during the night. And, and I can see now that I had just literally adapted to a lower level of functioning. And I know this because like, I didn't even know what I was leaving on the table. Like, it was just like, it's one of those moments where you're like, you know, I thought I was being so productive and I, and I was by all intensive purposes, very successful. You know, we won 12 Ivy league championships in 13 years and a national championship. I had, I was coaching Olympians. I was, you know, I got my master's,

you know, I did, I was doing a lot, but when I look back on like my health, I was a mess, you know? And when I first got my data, I was probably 15 years old biologically relative to my chronological age. Wow. And I've been able to completely reverse that. You know, now it's in the other direction and it's been eight years of work, but a lot of it is just literally was my first place I started was, all right, I was like, I'm going to stabilize my sleep-wake time. I found a, I saw a paper in 2017, you know, Andrew Phillips published this paper. He's a, he's a super famous sleep, sleep scientist and does all sorts of stuff with circadian rhythms. And he did a study at Harvard and, you know, looked at the students and was just trying to understand, okay, what is going to predict GPA, you know, thinking that it could be sleep duration, it could be all sorts of things.

And, and sure enough, he found that the students who had the more stable sleep-wake time had better grades. So I was kind of, and then I, and I was seeing it in my, in the whoop data as well. I was looking, I had, you know, under my purview, I had thousands of collegiate athletes. And again, the one thing that predicted injury and illness was sleep-wake time and sleep-wake variability. So I was like, wow, this is like key. So I started, I just was like, that's all I was focused on. I'm like, all right, what are the behaviors that lead that are going to enable me to fall asleep at a, you know, at a similar time each night, what do I need to do in the lead up to bed? And then I started

really getting in circadian rhythms and that's what, you know, kind of led me to, to, to pursue my PhD and kind of in this focus area. But it has totally transformed my life in terms of my own health. You know, I went from a 60 HRV when I came on the platform to, you know, now, I mean, today my HRV was 140. You know, my resting heart rate's 49. I'm 50 years old, you know, like, you know,

it's, so it's really, it has, it's completely transformed my life, aligning my circadian rhythms. That is really empowering for people who think that the way that they feel right now is the way they have to stay. And it's simply not true. You can change any time you want. Yes, for some people it's harder than others, but actually a lot of the time it's not as hard as we think. We don't necessarily need a huge lifestyle overhaul. A few simple things done consistently really very quickly start to move the needle.

You said it's been eight years of work. I found that really interesting, that phrasing, because I imagine some things are tougher than others. But I imagine also there's been a feed forward cycle whereby it was hard initially, but then you start to feel the benefits. It's just a way of life now. Yeah. And then you want to continue that way. That's how I feel. I love living in good circadian harmony. I just feel great when I do it. I know. I know.

Yeah. I don't think until people get to that point, they understand how motivating feeling good is. And when you don't do it and you feel off, like you're like, I don't want to do that again. I don't want to do this. So for example, I don't drink alcohol anymore. Now I would never say I'll never have a drink again. I may do, I may not. All I can say is at this moment in time,

given what I have to do in my life, you know, I may not. All I can say is at this moment in time, given what I have to do in my life, you know, I'm happily married. I've got two children who I like to see and spend a lot of time with. I helped to look after my mother. I have a pretty busy and full on job. Like I, I don't want to leave four or five hours on the table one morning because I had two glasses of wine the night before when it affected my sleep. So no one had to tell me to stop. I just did it enough times to realize, you know what? I prefer feeling great when I wake up and having a sharp head. Do you know what I mean? That's how it is. People have to experience it for themselves, don't they? Let's go to sleep wait time, right? Because I've heard you say before that

if there was one behaviour you would recommend to everyone, if possible, it would be to have a consistent sleep-wait time. Let's unpick that. What exactly do you mean? And why do you think this is one of those top, top behaviours for people to do? top behaviours for people to do. This episode is brought to you by Airbnb. Now I've been using Airbnbs for many years now for pleasure and for work. And last year when I was in London for a few days of work, instead of staying in a hotel, I stayed in a wonderful Airbnb, which was centrally located and had a really nice kitchen, so I could start off each day with my own food, just the way I like it. I've also just booked an Airbnb for a work trip to Oxford, in which I plan on recording a few episodes of this podcast. Now over the summer, one of my best friends from university told me

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So when we, you know, really is about boundaries, about, hey, how do I actually practice being the person I want to be? How do I practice living my values every single day? And for me, this was the path. And it started with sleep-wake time, really because, again, you know, And for me, this was the path. And it started with sleep-wake time really because, again, you know, I have access to all of these data and, you know, millions and millions of sleeps, you know, and many of our studies were also looking at measures of psychological functioning. So things like workplace resilience, feelings of control, feelings of purpose, feelings of efficacy, and homesickness

in military populations, contributions to teams and frontline healthcare clinicians. So we're talking about massive data sets. Could you just explain that, actually, before you get into this, the people who don't know what you do in your job and your role with Whoop in particular, if you could just explain this data you have access to, how much data is it? Because it's citizen science, isn't it? It's a very different way of doing science than what we're conventionally used to. Yeah, so the citizen scientist stuff is a lot of the

retrospective analysis. So going back into our data set at Whoop, which is basically Whoop is a physiological monitoring device. We are capturing heart rate data at very high frequency. We're transforming that data and giving our members insight into their sleep, insight into their recovery, okay? So their capacity to take on strain and insight into their cardiovascular load, we call this strain. And when we coach them, we get feedback. As a result, we get massive amount, I get massive amounts of de-identified data from our members. And there's also running alongside folks are journaling. So we know when folks are breastfeeding, when they are on their menstrual cycle, we know when they're drinking alcohol, when they're reported.

So we have these incredible data sets to be able to look at retrospectively. So we don't go on fishing expeditions, really, but we pre-register everything. So my team will pre-register before we go in and look at the data. We develop a hypothesis. We do, you know, we do a very traditional scientific method. We register it. So when we publish it, people can go on the registry and see, okay, this is what they said they did, what they were going to do. This is what they did, right? This is where it lines up and where it doesn't, right? So we're not just, you know, cherry picking, right? We don't want to do that.

So my team will do retrospective analysis, but we also do prospective research, which are, you know, like with a thousand paratroopers in Army Alaska where they're wearing boop device. And then also there's also an intervention, right. Where we're giving them a roster of some of these circadian alignment coaching behaviors. And then we have a control group who's not getting any of that. They're

getting generic sleep advice, for example. So we don't, we'll do, I'll do research on those folks. I'll do you know, I've done, I'm sitting on probably the most physiological data of, of, of frontline healthcare clinicians of anywhere on anyone in the world. We've done, you know, I've done, I'm sitting on probably the most physiological data of frontline healthcare clinicians of anywhere on anyone in the world. We've done, you know, Stanford Medical, UCSF, Las Palmas. We've done, you know, we're doing lots of work in those populations trying to understand circadian rhythm disruption, how this impacts psychological functioning, how it impacts functioning on teams, how it impacts things like psychological safety, also corporate executives. So in my role as global head of human performance, principal scientist at WHOOP, I'm basically in charge of kind of looking at both doing retrospective and prospective type of research so I can understand what behaviors are going to move around our sleep, our recovery, and our, you know, in our training, our ability to train. So, yeah, so that's kind of like my day job.

What I find really interesting, you have access to all this data, but these, yes, you have, you know, different professionals, people in the armed forces, healthcare professionals, but you also have a lot of data from regular members of the public. General population. Busy people with busy lives trying to juggle everything. You're seeing in real life what are the consequences of their behaviors on their physiology, which I think is really, really interesting.

Okay. So with all that data, having done this for years and assessed it multiple different ways, on multiple different occasions, you have concluded, along with the research, that a regular sleep-wait time is one of the top-line behaviors we should all be striving for? No question. Yes. I mean, I think it's, it, I, I will go on a limb and say that I think it is the most important behavior. If we're talking about wanting to really optimize our health and longevity. I think when we, when we have a stable sleep, wake time and we're getting sufficient sleep matters, right? We need to spend enough time in bed, right? There's no question. And I think, you know, that sweet spot for folks is somewhere, you know, between seven and eight hours for like adults. And I will say that when folks

start to stabilize their sleep-wake time, they actually need to spend less time in bed because their sleep becomes more efficient. They don't end up with kind of that, you know, they end up with less light sleep, less awake sleep, right? Because their sleep becomes more efficient. So this is different than sleep-deprived sleep where you end up with, you know, massive amounts of time and rather than sleep. And that's obviously, it's compensatory. It's important. Our bodies need to be able to do that. It's functional, but you don't want to be doing that chronically.

Right. So anyway, yes, sleep, wake time bubbles up in, in, in all of our research as predicting both psychological functioning. In fact, we did around COVID we did when Dr. Chuck Sizer was on this paper as well. We basically looked at, we sent a survey out to all of our members, 70, when Dr. Chuck Seisler was on this paper as well, we basically looked at, we sent a survey out to all of our members. 70,000 people replied to our survey. It's a 20-minute survey where we were just asking all sorts of mental health questions, lifestyle questions. Do you have kids? Do you not have kids? Like, you know, it's the whole nine yards. It was

a very thorough survey. We were asking all sorts of questions about their lifestyle. And basically the end result of that study, and we looked at, because these were all members on our platform, we had the three months prior to lockdown and then the three months after lockdown. And the one behavior that we saw that was most protective of psychological health, mental health after lockdown was sleep-wake timing. Now, how much does it matter what that sleep-wake timing is, or is it the point that it's a consistent sleep-wake timing day-to-day? Okay. So there's a couple of things there. So one of the things that we're starting to see is that, so in the healthiest population on our platform, the 18 to 23 year olds who are collegiate athletes. Okay. So we're talking like tip of the spear, genetic motto, congratulations.

You know, these are really high end athletes. So when you look at that population, after one hour of variability in their sleep-wake time, that is when we start to see a degradation in their heart rate variability and a degradation in their resting heart rate. So heart rate variability is basically a measure of our ability to respond and adapt to life stressors. When our heart rate variability is suppressed, that means our body has taken on load, life load. It could be a combination of training. Maybe we drank a lot of alcohol or we had a super

heavy meal. That is going to suppress our HRV. A fight with your partner, too much work, you know, all sorts of stuff. Psychological stress. Absolutely. Basically a low HRV is going to produce kind of a higher baseline heart rate, resting heart rate. You're going to hum a little bit less efficiently. Your body's going to have to work a little bit harder. So heart rate variability is an incredible proxy for just our mental and physical health resilience. Incredible proxy for that. And we see in the data that when we start to get outside that hour of variability in this very healthy population, just one hour, we see a sharp decline in their HRV and increases in rest and car rate. So clinically meaningful in both directions.

That is just one hour, just a one hour variation. One hour, one hour. That is what I would argue that many people do that every Friday and Saturday nights. Social jet lag. They have a rhythm in the week and they let loose on a Friday and Saturday, but that has a consequence, doesn't it? I mean, social jet lag is the other thing. Like want to try to, again, across the seven days, you want to just try to have stable sleep-wake time. You don't want your weekday to be a lot different than your weekend in terms of variability.

And we see, there was a really interesting study, social jet lag and other aspects of sleep are linked to non-suicidal self-injury in college students. This was an 885-person study where they looked at their whole entire history of non-suicidal self-harm and then the three months of the study. And basically they saw that for every hour of variability between week, day, and weekend, there was a 17% increase in non-suicidal self-injury. I mean, this is just remarkable. It's wild, right? And yeah, I mean, it's just this confusion and this misalignment. It has just profound effects.

And I think what's like insidious about this, and it's like you just start, and this is what I saw in myself, you know, it's like this just this really insidious, slow decline, right? And it's just every day you get a little less capable of being the truest version of yourself and like maximizing your potential. You know, like you just get a little bit further away from that until you literally adapt, like I said earlier, to this kind of lower level of functioning mentally, physically, emotionally, you know, your ability to kind of engage in your life and be present. And it just is diminished, engage in your life and be present. And it just is diminished, right? And this is kind of the root, right? And that I think we're just not having a clear enough conversation about.

What kind of variability do you think we can tolerate and still have optimum functioning? Because we're not, we're the best one in the world. we may not fall asleep, but our eyes may not shut at exactly the same time every night, despite our best efforts. And when people are trying to incorporate a more stable sleep-wake time, the most important thing is to wake up at the same time every day, which you can control, and view light. at the same time every day, which you can control and view light, even if it means potentially having a bit of a shorter sleep, that, that same wake up time is absolutely critical for setting your circadian rhythm, right. And dropping that melatonin at the time that you need to, right. To fall asleep and stay asleep. So that, that, that's like when we talk about the coaching piece of circadian alignment, that's where you start. You wake up if I, if you know, all right, I want to wake up at seven.

You, you wake up and literally as soon as you wake up, get yourself out of bed and get out into the morning sunlight or the morning natural light. It doesn't have to be sunny out, but just, you want to get out in a natural light. You want to look up at the sky, you know, for at least five, you least five to 10 minutes and then go about your day. That's going to help set your circadian rhythm. Okay. So this is super fascinating. Okay. So we want consistent sleep wait times. We're recognizing that it can be challenging for people in different jobs and different points in their life. But if possible, you're saying one thing you should try and control as much as possible is the same wait time every day. And you are arguing that perhaps,

even if you're sacrificing 20 minutes or 30 minutes extra sleep, the benefits you get from that consistency outweigh the negatives of not getting enough sleep. Can I just say in my own experience, and this isn't an equals one, that is absolutely true for me. There's no question at all. I am someone who, well, I think we all do. I thrive on rhythm. I am my best version of myself when I'm asleep by nine o'clock and I'm awake by 5 a.m. When I do that regularly, I'm flying. Just firing it all still. Yes. Sport, parenting, work. And when I shift off, when I think,

ah, you know what, I'm going to watch something tonight on Netflix a bit later. And, you know, I could tolerate it for one night. But I'm not as good the next day. I'm really not. I don't know what, what's your, I mean, if you're, if you're open to share, you look fantastic for being 50 years old. Thank you. What time do you go to bed and what time do you wake up? Yeah, I'm same, you know, around nine 30. I'm usually asleep by 10 every single night. Same. You know, around 9.30, I'm usually asleep by 10 every single night. And I wake up around 6.15, I would say, pretty much on the dot. But you've got your rhythm that you try and stick to, basically. Yeah. So based on the data, I keep my sleep debt under 45 minutes.

What does that mean? So sleep debt is basically, Whoop has a feature that it basically tells you kind of what you need based on how efficient last night's sleep is, your baseline sleep. So kind of my sleep characteristics over the last four weeks, and then any naps I might have taken and how much load I put on my body during the day. It might say, hey, you need like 12 more minutes of sleep because you really had a super active day, which makes sense, right? Physiologically. So sleep need is not perfect, but it actually, I've been able to validate it with some, with NBAC and Stroop. That's another study on psychological safety that was really fascinating. But so sleep debt

kind of correlates with these kind of performance metrics that we care about. So it's not a random number generator. There is something to our sleep need calculation. So I do listen to it. And, and in fact, I've seen in a study with 230 collegiate athletes, I've seen sleep debt correlate to, um, so when, when athletes are, um, taking on more than 45 minutes of sleep debt, we see there, there are more, uh, they're predisposed to illness and injury. Folks who basically keep it under 45 minutes are essentially bulletproof. So again, seeing this data, I've basically adopted that. And I have not been sick in, I'm going on eight years. Wow.

I did not get COVID. I have not a sniffle. I had a headache. I got a little dehydrated after a long run. I had a little bit of a headache, but I literally have not been sick in like eight years. And that's really the important point, isn't it? Because we spoke at the start about the importance of a solid circadian rhythm. We spoke about the importance of matching our external behaviors to our internal clock. That affects many things. We mentioned risk of cancer, weight gain, longevity, brain function, energy, but we didn't mention our

immune system, right? And you're just speaking to that now because I delight you. I'm so passionate about this. A good, robust circadian rhythm. It impacts everything, including your propensity to get sick. It sure does. Yeah. And I think it kind of goes back to mechanistically, when you think about when these stress systems are activated chronically, that is when you get sick, right? So HPA axis, autonomic nervous system, and your immune system, right? When they're having to work overtime, you are going to be more vulnerable to illness and disease. It's just the reality of the situation, right? So it's about finding that point of stress. Stress is really good and super important, but there is a point of diminishing return, right? And that's where we need to kind of figure out what is that horrible level of stress? Like,

how do I create enough buffer in the system that I can tolerate these moments where I have a lot of stress? And buffer in the system is minimizing sleep debt, keeping it under 45 minutes. And I would say from a variability perspective, and this is kind of your original question, and I would say from a variability perspective and this is kind of your original question the other marker I used to look at is sleep-wake time and I try to keep my variability below you know around 30 minutes. So as a recommendation for people try and have the same bedtime and the same wake time if you're slightly off on your bedtime try and keep the wake time consistent. If you do need to shift it a little bit day to day, try not to more than 30 minutes or so. Is that kind of the essence of the sleep-wake recommendations? The older you get, the less tolerable your system is going to be to variability, right? You're going

to be more sensitive, right, to variability. Now, within that 18 to 23 population, you know, we have some folks who are really sensitive and some folks who are. I'm just talking about the mean. Right. So of that group was basically one hour. Right. So, you know, it stands to reason that if this group is super fit and and, you know, young tip of the spear athletically, if their tolerable level of variability is one hour, it stands to reason that's going to just keep getting... Again, we have to prove this out in the research that we're doing across all the populations. But I feel like that's probably what's going to happen, right? We're going to start to see this kind of window narrow as folks age. Now, I believe that you think a close second to sleep-wait time is a regular eating window. Is that still the case? And if so, what is your advice and what are your recommendations there? Okay, so there's a couple things with the timing of your eating. So we see at population level,

So we see at population level, it is second only to alcohol in terms of its ability to disrupt our sleep and markers of recovery. So when I say markers of recovery, I'm referring to heart rate variability. I'm referring to resting heart rate, respiratory rate. These are kind of our markers of recovery. And then sleep, referring to our ability to get into these deeper stages of sleep. So REM and slowly sleep and minimizing our awake time. We're going to have light sleep. That's totally normal and desirable. It's important.

There are really important things happening during light sleep. But we want to have about 40% of the time that we're spending in bed. We want to be in these deeper stages to restore. So the only thing that moves around our sleep more than alcohol is a late meal. So we're talking like millions and millions of sleep, right? And millions of people kind of reporting over time, right? Like, you know, we're looking maybe at three or four years of like people reporting late meals. And there's just no question that it has a negative impact on recovery and sleep. So given that, you know, it's interesting, we spoke before how we're not as different as we

might think. And I agree with that. At the same time, I believe there is quite a lot of individual variation in terms of, let's say, the diet we might thrive on, for example, or the movements and the exercise regimes that work really well for us. So I'm really interested. And this is where I find the data that you guys are capturing at Whoop really, really interesting compared to, let's say, a more conventional scientific experiment where people are brought into a lab and they're taken out.

The numbers are so small. You can't do within-person statistics, right? Like you can't do multi-level modeling, right? When you have an N of 13. And that's where this is like so exciting is that we can look at, we can do within-person analysis, right? And between-person, within-person, between-person

across like hundreds of thousands of books, right? So we can actually get person, between person, across like, you know, hundreds of thousands of books, right? So we can actually get to a place where we're saying, hey, this isn't just population level, this is like within person, right? And then we really start to understand, we beat down the variability in a way that, yeah, these traditional experiments can't. So for someone who, let's say, can't afford Whoop and is like, okay, I want to implement stuff from what you have learned from all that data, but I can't go on that platform myself. Are there any consistencies as to food timing in the evening and its impact on sleep? Some people are going to be more tolerable to a late meal than others, but can you make a generalized recommendation based upon what you've

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100%. So, you know, there's lots of other kind of external literature that supports this as well. So this isn't, you know, just our research, but what we've seen is that, you know, this, this concept of time-restricted eating, which is not intermittent fasting. Okay. And to become not a nutritionist, I can just talk about timing of things um as someone who studies circadian rhythms um but you know time-restricted eating and intermittent fasting they're often conflated in in kind of discussions on the internet and whatnot but time-restricted eating is basically just um consolidating your your eating window during a period of time um during the hours. Okay. So in that window can be eight hours. It could be 10 hours. It could be 12 hours. Right. But the key is, is you want to eat a bulk of your calories when it is still light out. And then after the sun goes down,

we're really not meant to be eating food. We're not primed to metabolize food. And we know from the studies that have looked at insulin at different points of the day, we become way more insulin resistant as the day progresses. So you want to have like a big nutrient dense meal early in the day. Breakfast is so important, especially for women need to be eating breakfast.

Lunch is really important. We want to need to be eating breakfast. Lunch is really important that we want to get tons of protein, lots of veggies. Like this is when we're like really primed and metabolized. And then as the day progresses, we want to, you know, decrease our, our calorie intake preparing for sleep. Cause once we sleep, once we fall asleep, what's happening mechanistically is you have a competition, right? Between digestion and sleep. They can't do both at the same time, right? You're still going to fall asleep, but you're not going to be, it's kind of like alcohol.

You're asleep, but you're not in these deeper stages of sleep. So that, and that's what we see in the data. We see that these late meals are compromising deeper stages of sleep. People are spending more time in light sleep by the tune of 30 to 50 minutes. So this is like meaningful amount of time awake. Okay. And an average decrease in sleep efficiency by up to 17% when folks are reporting late meals.

It's like wild, right? So food within two hour bedtime. So the recommendation is you wanna try to back up your mealtime. So you're giving at least a two hour buffer from your last calorie to when you intend to sleep. And just general rule of thumb, bulk of your calories when you're meant to be active,

which is during the daylight. So that's a really big piece to this kind of whole puzzle of also being able to maintain sleep consistency, right? Different foods will potentially impair our ability to fall asleep. That said, I did a study with 700 collegiate athletes where we looked at pre-sleep feeding. And it looks like a bolus of protein that's bioavailable is not really going to impact your ability to, you know, fall asleep and stay asleep. I think it's if we're having that big Indian meal a couple hours before bed, that that's the one that's going to like kind of hit us hard. Yeah, that's really interesting. So, okay, let's unpick that a little bit. Well, I'm very conscious these days, Kristen, more than ever, that we're living in a world of

increasing health information on podcasts, on social media, in the media, And it's not always the same, right? Sometimes people are hearing conflicting information. And so, I mean, I have my own views on how we solve that. But in terms of what you've just said, many people have heard over the last few years that this whole idea that breakfast is the most important meal of the day is not necessarily true. Many people practice intermittent fasting and they'll have coffee in the morning and they'll delay their first meal to let's say 12 o'clock and they'll eat their second meal at 8pm. And they will say that, hey, they're thriving living like that. They're eating good quality food. They're not overeating. So there is an individual variation, I think. But I also agree with what you just said in the sense

that all the literature I have seen around circadian rhythms, yes, light is the number one influence on our circadian rhythms. But I think food is number two from what I can tell. And they're sort of saying there's some really good Spanish studies showing that if you have the bulk of your calories in the first half of the day, so let's say before 3 p.m., you know, it's better for weight loss, it's better for blood sugar control, better for sleep. And that study controlled for diet too, which was awesome. Everyone was eating Mediterranean diet. But yeah, folks who were eating after 3 p.m., yeah. So I agree. So on a personal level, a few years ago, I did buy an Oura ring.

I found that I learned within six weeks, maybe less, I kind of feel that I learned what it was going to teach me. And one of the key things I still remember was a late dinner massively impacted the quality of my sleep. And I could see it on the data there. So here's the problem, right? Here's the problem these days is that you may want to live in perfect circadian alignment, but society isn't really set up to support that, right? So for me, sitting down with my wife and children at the end of the day is quite an important family moment, right? So sometimes it does slip on.

But having said that, having kids has been the best thing for my circadian rhythm because everything gets shifted back. And I eat early with the kids and I have done for years, right? So I guess what I'm trying to get to is for someone who just heard what you said, who is saying, you know what, I hear you, but I'm thriving on intermittent fasting at midday and 8pm and I've got energy and focus. What would you say to them?

what would you say to them? I can only go back to the literature in terms of what I know and in terms of how we produce insulin and when we're most resistant and sensitive. And so that said, I think if people are eating low glycemic kind of foods, it probably is less important, right? I think it's really, if we're just eating, you know, really fatty, um, you know, high carbohydrate kind of foods,

you know, we're over fueling. Um, I think that's when it becomes problematic eating later in the day. But I do think if we're eating really cleanly and we're keeping kind of our blood sugar at bay, I don't think that that's going to have a huge impact on sleep and recovery. So I do agree that there's variability. I think we can't really ignore the science though, that the morning timeframe is really when our body is expecting food and when we're really optimized to accept and utilize those nutrients. So I think we're probably not able to capitalize on that meal as well at 8 p.m. as we are at 8 a.m. And I think that's just the reality of the situation. I love that. And I think, again, going back to these vicious cycles we get into

with our behaviors, if you're eating a large meal at 8pm and you think it's not impacting your sleep, okay, let's just accept that for a moment that it isn't. You're not going to be hungry first thing in the morning. And so you think, again, you reinforce the belief that, no, no, I'm not hungry in the morning. But I've done this with patients. I've done it with myself. If you bring your dinner time earlier, if you have a lighter meal, let's say you do eat with your family. This is what I do sometimes. I'll have a soup or a bone broth in the evening. So it's a lighter meal, even though I'm having it maybe closer to bedtime than I would want. So it's going to be easier to digest. 100%.

Then you are hungry in the morning. So it kind of, all of our hunger cycles, our energy, when we feel sleepy, it's kind of all impacted by what we did the day before, what we continue to do. Do you know what I mean? And I don't think people really deeply understand that yet. Yeah. I think it's, you know, there's a phase relationship, right? And Dr. Samer Hattar, one of mine, you know, I just love him. He's done incredible research in the area of circadian physiology, circadian biology. But he always, he says that there's a phased relationship, you know, between our activity, our meals,

our sleep, you know, when we view light. And I think to ignore these relationships really comes at an enormous cost, you know, to our health and our functioning. So I think we have to respect this relationship. And, you know, I don't think there's a single reason why we shouldn't try to respect this relationship and you know i don't think there's a single reason why we shouldn't try to optimize for it you know um and and i think like kind of goes back to just reconfiguring your family a little bit you know and i have a couple teenagers

and we just have kind of reorientated ourself to be able to be more aligned with this natural light dark cycle. And, you know, fortunately, you know, my, my co-parents like super on board, like we're able to kind of navigate all that really well. But, but I think we have oftentimes with our partner, a lot of these like kind of hidden commitments that really, I think pull us a little bit further away from maybe our ability to kind of show up in the world as we want to. And maybe that's that glass of wine at nine o'clock or 10 o'clock or, you know, that we have regularly and, you know, thinking about, okay, maybe I can, knowing I want to maybe make some of these changes, maybe we can go on a walk instead, or, you know, how do you kind of replace

some of these behaviors that are getting in the way? And I think, so I think when folks maybe hear this conversation, like, it's easy to get a little overwhelmed, because they're thinking about all these commitments that they have with their partner and their family that that kind of don't align with this way of living. But it's just a matter of, you know, just reconfiguring. Yeah, that's a great point. As on reflection, I don't think I've been out for dinner with my wife. I don't know, in over five years, but we've been out for lunch, right? You know, when we were dating, we would have gone out for dinner all the time and stayed up late and all that kind of stuff. But it's kind of interesting that we just realized that we don't want to be out in the evenings for dinner. A, we've got kids. But B, it just doesn't suit the rhythms. And then my sleep in particular doesn't

suit if I'm eating late. So that's interesting. You know, if I think about these top two behaviors that you are talking about, a consistent sleep-wait time and a consistent eating window, and ideally finishing two to three hours before you want to be falling asleep. Rhythm underpins those two behaviors, doesn't it? You know, going back to circadian rhythms, those two are all about rhythm, a consistency with our rhythm. And again, I will share that I mentioned my sleep-wait time, nine till five is when I'm at my best. But when I'm eating consistently for me in a 10-hour eating window that's the same every day, when I can do that consistently, I just feel my best self. And when I move off it, and occasionally I will, you know,

I'm in London for work and there's a dinner. I'll always try and do it earlier, but I'm never quite on it the same day. You know, the next day I'm never quite on it like I want to be. Yeah. It's kind of one of those things where we plan so many aspects of our lives, but we don't necessarily plan, I think, some of the most important things in our lives, like this, this foundation, right. That's going to allow us to, you know, pursue our, our, our values in, in a way that feels really amazing to us. Right. And, and I think that's kind of, there needs to be some, some pre-planning in order to make sure on average, you're able to kind of hit your sleep weight targets. You're able to,

you know, keep your feeding window, your eating window inside 10 hours. Right. Um, and, and I, and just a quick distinction between intermittent fasting and time restricted eating. I'm going to say this before, um, intermittent fasting implies like some like caloric restriction, whereas time restricted eating. And again, going back to this notion that it's free, democratically available, even if you cannot afford really nutrient dense, high quality foods, you can control when you eat your food. Right. Even if the food is not like as great as it should be, you can get really close to your metabolic goals if you're eating during the daylight hours. Yeah, I remember when I first found out about Sachin Panda's research, maybe seven, eight years ago, some of the early mouse studies. And I remember a graphic with the mice and how even if they weren't eating junk,

but they were doing it in a confined eating window, the negative impact was just much reduced. It was fascinating. I have the same graph in my mind. Yeah, it's this beautiful graphic. It was just like, oh, wow. I think it was the first time that I saw something that really connects with me, something I already intuitively knew, which is that I thrive on rhythm. But when I saw that, I thought, wow, rhythm, rhythmic living is very, very important. And that's what the modern world has taken away from us. It's kind of decimated that rhythmic nature of life. You know, on that, one thing I'm interested in when you look at your data,

in, I think you're on the east coast of America, right? That's right. So I live in the northwest of England. And there's a huge variation between light-dark cycles now as we're recording in nearly mid-summer here in the UK, right? So it doesn't get dark till maybe 10.30, 10.45 PM. And it's light at maybe 4.15 AM, something like that. And then, you know, in November and December around Christmas time,

the kids are coming home from school at 4.15 and it's dark, right? So do you see in the data that our requirement for sleep changes according to the seasons? Yes. Shorter in the summer, longer in the winter. We're meant to just kind of adapt to the seasonal variations. Yeah. It's rhythm. It's again, it's rhythm. It really is. But people spend 97% of their adult lives indoors. Yeah. So we're missing the number one input, which is lights. Yeah. Natural light, right? Like artificial light, you know, obviously, you know, after the sun goes down, we have not adapted to blue light after the sun goes down to be really clear. So that's a lot of the consequences

that we're seeing with regard to health. But yeah, I mean, just light during the day. I mean, certainly, you know, as the sun is setting, you know, light in the morning when it can impact our circadian rhythms, right? So there's kind of like the circadian dead zone between I think 10 a.m. and 4 p.m. generally. So that's why like that morning bookending your day with light is so important to set your circadian rhythms. So before 10 a.m. and as the sun is setting, you know, you want to get outside in the light for a minimum of 20 minutes. And then we know that the bare minimum that folks should be spending outdoor is 67 minutes if we are interested in mental health. So just the natural light in general has such an impact on our skin health, on vitamin D, our mental health, our mood, our alertness.

So important, right? Did you say 67 minutes? So important, right? Did you say 67 minutes? Yes, that's what we know. That's kind of what's been defined in the literature as being like the minimum effective dose of natural light is 67 minutes for humans. Yeah, I mean, that's fascinating. And I think that makes complete sense.

I mean, we've evolved outdoors. We've never spent this long inside. 67 minutes, though, to some people will be like wow an eternity yeah i'm like i'm nowhere i'm nowhere near that and i know i mean yesterday i you know i'm finishing my my dissertation about to turn it in um but i mean i was i did not spend 67 minutes outside yesterday but i'm acutely aware and i think if this goes back to the scheduling piece we're talking about is like you you just have to really, you know, if I know today, fortunately it's a, it's a holiday and I'm going to, I'll be outside all the rest of the day,

you know, I'm going to kind of make up for it. And I think that that, you know, it doesn't, it's not a perfect science, but that's kind of in my head how I think about it. And I just try to, on average across a month, schedule my time so I can hit these minimum thresholds. And that's really how I'm operating. There's also research now, isn't there, that children, I think, who are not spending, I think it's two hours of time outdoors each day, have got an increased risk of myopia yes which is really yeah really really interesting yeah when it's narrow like you outside you're forced to expand your your visual um you know system and and that is again when we think about how we've evolved right like we

haven't been we haven't evolved to just like be like this all day long you know which is what really people are when it and when you talk about phone consumption and being on screens. I don't know if you're familiar with this at all, Kristen. I work with one of the most incredible movement coaches I've ever come across. She's just phenomenal. And she's got a machine that's only about four or five in the world where they can track all of your movements as you're running on the treadmill, everything that your spine and your pelvis are doing. It's absolutely incredible. And she can interpret it really well. And here's the thing, when you are moving with peripheral vision, your movement is completely different and more fluid than when you've got concentric vision.

So one of the things we're working on is when I'm running is to have that softer peripheral gaze and you can feel more rotation. So your visual system even impacts the way that you move, which is utterly remarkable. It is crazy. I mean, just the panoramic vision. And I think what happens physiologically during this is like when we expand our view and kind of create this panoramic panoramic vision we decrease our heart rate and increase heart rate variability um so it's funny like when you rory mcelroy he's a super famous golfer he talks about this like he used to kind of after uh maybe a bad stroke or like just even because he's walking from hole to hole he'd look down at the ground and he learned about this research and, um, and started, you know, keeping his

shoulders back, looking up, expanding his vision. Um, we also tell kind of surgeons and, you know, folks in kind of these high stress, high stakes environments to expand their vision when they're feeling stressed because it immediately reduces your heart rate, increases your heart rate variability. So yeah, it's, it's kind of kind of cool to see how vision impacts your physiology in such a profound way. And then obviously biomechanically as well. Yeah, super interesting. Okay, you've touched on alcohol a couple of times. Let's talk about alcohol.

What have you seen in the data? Did you say food was worse than alcohol for impacting our circadian rhythms? It's second. Second to alcohol. Yeah, and I think like the, what's tough about alcohol is like, it's not just impacting you the day after it has like a five day tail. Wow. Yeah. So, okay. Let's unpick that. So you're, you're saying from the data you've seen and you're measuring people's heart rate variability and their load and their recovery. Their heart rate, their respiratory rate,

their activity levels. So you're saying that, and I want to know, what are we talking here? Because let's say someone has two glasses of wine, okay? And they feel that they were up a few times at night. They have a bit of a headache the next day, they're craving a bit more caffeine, they're extra hungry, but they decide to compensate. You know what? Today wasn't good. I'm going to go to bed early tonight, eat early, not have any alcohol, and they then get a good night's sleep the following day. I think most people would feel that they're back to normal the next day. It sounds like you're saying from the data that that's simply not the case for most people. Right. They probably feel better, but physiologically, they're not back to their baseline.

Wow. So if they're reporting drinking two plus drinks, okay, so two or more drinks, it takes on average five days to return to your baseline. Wow. I know. On average, of course, means that for some people that may be six or seven days and someone else, it could be three days. But that is exactly that is still just average across, you know, hundreds of thousands. I mean, at this point, millions, you know, of data sets, right?

Over, you know, the course of the time folks have been on the platform. Yeah, it's the average two plus drinks averages five days to return to baseline. And again, yeah, it could be two days for some, seven days for others. But this is where the problem lies, right? Like you basically inside that window of five days, you could be having more drinks, right? Like you basically inside that window of five days, you could be having more drinks, right? And, and so you just keep pushing, then that's basically what we see is, you know, folks who have, you know, history of, you know, pretty, you know, lots of alcohol consumption, they come onto the platform with very low heart rate variability.

Wow. Yeah. Now, we've all got a different tolerance level to alcohol. Okay. So from the data that you've seen, are there people out there who can maybe have a small glass of wine or half a beer in the evening and it not impact their sleep yeah i mean i think the key is to make it as far away from your um the time you intend to sleep as possible you know that's where it just kind of seems to wash away and not impact your sleep you know it's it takes about so stress monitor is a new feature that basically looks at your heart. It's an algorithm that's looking at your heart variability and your resting heart rate continuously across the day. And we basically map your stress on a scale of

zero to three. So I know I'm, I'm same as you. Like I don't really drink. I think the last time I drank, I don't even know, but it was a long time ago. But I basically, I had a Prosecco and it took four hours for it to clear my system. One drink. So, and I looked basically, I went to bed and I think I had the Prosecco at seven, maybe, you know, I went to bed at like 10. and the next day I look back on my data and my stress monitor data, basically what I was elevated in that usually when I'm sleeping, I'm in like one, a one stress, right? Three is super high. One is really low. So I'm 10.7, whatever. So it was basically, I was like 2.7, 3.2 was the highest. And then it kind of started to go down,

but it basically took four hours for that one prosecco to clear my system before i was like back down to like my typical stress level wow so the front end of my sleep was compromised after one drink and again that could just be my tolerance level to your point my weight like all of that is going to impact how it absorbs and how i digest you you know, and metabolize the alcohol. But I've had a theory for a while that is around our total stress load, right? So we've got all kinds of inputs into our life, work stress, life stress, emotional stress, training stress, whatever it might be. And so we've got a certain amount of headroom left

to deal with other stress. And so when I used to drink alcohol regularly many years ago... Yeah, you wipe away that headroom. Well, yeah, but what I noticed was that, let's say, I don't know, in my late 20s, for example, if I was a junior doctor, right? So busy, working shifts, night shifts, all kinds of things, right? So knackered all the time and just getting by. I would find that a glass of wine in the week, I just couldn't tolerate that well, right? Or maybe it's in my 30s. It was a while ago now, right? But there was a point in time in my life where during the work week, I realized that drinking any alcohol, it just wasn't agreeing

with me. But if I was on a holiday, so I was on a beach somewhere, it was sunny, I was chilled, I wasn't doing any work, then that same glass of wine wouldn't have the same impact on me. And I thought, wow, or certainly this, I wasn't tracking anything. This was purely my perception. I thought this is really, really interesting. Maybe it's to do with my background stress load and the headroom left that I have now to deal with this toxin into my body. What's your perspective on that based upon what you've seen? Yeah, I love that. I, you know, I, I call it kind of buffer, you know, you want to try to, I think the more external stress in your life, the more, um, you want to, I, you know, I, I, this is kind of like I say

with military operators, acute care surgeons, you know, people in these high stakes, high stress environments, I kind of say, Hey, this is the cross you have to bear like outside your craft because of its demands and the stress, just like you junior doctor, right? Like the demands and stress of just living that life, everything else kind of needs to be perfect. And that's, that's the cross that, that folks bear in these high stakes, high stress environment environments, right? If you, if you, If you don't want to compromise your health and your longevity and just kind of maintain a little bit of a neutral state, you know, pay down illness and injury risk, you kind of need to really dial in on your nutrition,

your hydration, obviously to the degree that you can stabilize your sleep-wake time, you know, just getting this bookend of light as often as possible, you know, thinking about your social connections, you know, surrounding yourself with people who, you know, nurture and support your values. So, so important. You know, so there's just like these things, like these boxes that you need to kind of be checking when you're in these situations where you have a lot of stress, you know, maybe you're caring for an ill child or a parent or, you know, like there's things that life is going to throw at us. Right. And, and I think, and we're all going to face these moments. And I think that's kind of why in some ways, like I try to live the way that I do is like, I know I'm going to

encounter those moments and I want to be ready for it. You know, I want to be able to, um, to handle it, you know, with, with, you know, a sense of balance and proportion and grace. And, and if I am, you know, all over the place with my lifestyle, I'm just not going to be able to do that. So I think there's this thing about creating buffer in the system to be able to deal with the natural kind of variations in demand and priorities across, you know, a month, a week, a month, a year. Yeah, I appreciate you sharing that. Before we move on from alcohol, just to sort of finish off then, do you think that some people can tolerate a little bit of alcohol without too much of an effect on their sleep and or their resting physiological states? You know, are some people, you know, can they metabolize it better and they

can deal with half a glass of wine three nights a week and they can still function well? Like, do you see people on the platform where you go, actually they're drinking, but it doesn't seem to be affecting them much no wow no one is immune to um that i've seen when people drink it impacts their resting heart rate and their heart variability and their respiratory rate wow and their their sleep markers like it just is it's pretty ubiquitous i mean there might be the outlier here and there that you know i i can't you know i'm not gonna do a statistical fistfight with those folks but um but but i can say that you know from what i've seen in our data you know which is massive amounts of of data at this point um it appears that no amount of alcohol is good for your your resting physiology

okay thank you for sharing that okay so i mean that's pretty clear on your view on alcohol and what it's doing to us it's so hard seeing the data it's really striking you know like it's like very hard for me to have any other point of view because I see it so black and white, clear as day. I think I saw that also when I was wearing a tracker. And I think I also, from recollection, saw that, wow, this is what a glass of wine is doing to your sleep. And once you've seen it, and I guess some people need to see it over and over again, but for me, I saw it to go, okay, I get it now. I can see what's happening. I can feel it subjectively and I can see it in the data objectively. So both of those

things together are sending me a strong signal. What's the deal with caffeine from what you've seen? Yeah. So, you know, again, same sort of thing as alcohol, like we all metabolize it a little bit differently. Some people can metabolize caffeine very quickly. Others are slow metabolizers. So I think understanding kind of where you sit is important. But yeah, I mean, generally speaking, we see caffeine after 3 p.m. impacts sleep onset. So when people fall asleep, changes, it delays when folks are drinking caffeine after three wow yeah that one's like pretty clear do you understanding that we're all different and that if we don't have access to our own data, we have to go on generalized

recommendations, you're pretty confident that you can make a recommendation about sleep-wake time, about eating windows, about alcohol, like some universal recommendations for people. Yes, of course. Do you have a universal recommendation regarding caffeine? a universal recommendation regarding caffeine? Yeah, I would say most folks should probably have their last sip of caffeine by noon. Yeah. And I would say for folks who have short sleep, so let's just say you had short sleep, you're waking up at that normal, your body is going to wake up. If you've been waking up relatively consistently, your body is going to naturally, that cortisol, that balsal

cortisol is going to just happen on its own. So you're going to kind of wake up or want to wake up at that time, even if you've had short sleep. So let your body wake up at seven and actually don't have caffeine, but actually take a nap at 11 if you can. That's like the best way to deal with short sleep and maintaining circadian rhythm. Have a bit of a rest that doesn't impact your biological sleep at night. So any naps you want to kind of try to take before 1 p.m. and then same philosophy with caffeine. I would say 1 p.m. would be like the hard stop for, in my view, for naps, based on what I've seen the data, and caffeine. Yeah, I think that's such a great point about naps. It's something I've done for many years is if I'm able to, it depends what my work is for that day.

But if it's a work from home day to have flexibility, for example, then I will maintain my 5 a.m. wake up time and I'll just try and get a mini, a short nap at some point in the day if I can, even if I don't even sleep and I just shut my eyes for 20 minutes. It is amazing what benefit that has. Yeah, we just did. We're about to analyze our Yoga Nidra data. I have a script out there on the internet that I did. We use this with frontline healthcare clinicians because, and elite athletes, like a lot of folks in these kind of high stakes, high stress environments struggle with napping

because they're just chronically activated. But yoga nidra, which is just basically a mind body scan is just an awesome alternative to napping and actually mimics slow wave sleep. This is not research that we've done, but external research to whoop that I saw that was really cool. So yoga nidra is another kind of strategy I think folks can deploy when they have short sleep and they're looking to increase their alertness. Can you explain to people what that is for people who've never heard that term before? Yeah. Yoga Nidra, it's a, it's a yoga practice and it, it basically involves just very simply a mind body scan. And you just listen to a script, 15, 20 minutes. I

think there's some 10 minute scripts out there. And it basically just kind of takes you head to toe where you just journey through sensing different parts of your body. You don't move. You just kind of sit there and you're in like this awake state that feels really meditative. Like once you get going and you just feel really calm and centered, it's, it's pretty amazing. And you actually might fall asleep. So it's good just even if you, to start with this yoga nidra practice and, um, and you actually might fall asleep. So it's good just even if you to start with this yoga nidra practice, and you actually might find yourself being able to nap because it really does. Again, if you're if you are actually carrying a bit of sleep debt, you're going to feel sleepy. And and

you might actually fall asleep with this yoga nidra. Yeah, it's something many people find useful. There's loads of free kind of scripts there on YouTube for people to check out and find one that they like. It reminds me of a post, a friend of mine, Brian McKenzie, I think you might know as well. Yeah. Like I had Brian on the show a few years ago. He's so good. He's great. I think he did a post on Instagram a few years ago. I think his dog had fallen asleep in the afternoon in front of the fire. And I can't remember what he said,

but it was something like, that's the kind of stress response system type vibe we need. We should be able to just switch off and take a nap like a dog can. But the fact that we can't is because we've got all this stuff in our head and we're overthinking and we're ruminating. And that really connected with me because I thought, you know, that's hard for many people. I found that hard in my life at various times and I still

can do if I've got too much on my plate. So I just thought it was a beautiful image to go, wouldn't it be nice if humans, if we could, you know, just switch off and take a nap on tap when we need to? I mean, I think that's the superpower of the 21st century is being able to be, you know, activate when you want to activate and deactivate when you want to deactivate and having enough buffer in the system to be able to kind of fire up your autonomic nervous system, like on demand. Yeah. You know, and, you know, be able to intentionally increase your heart rate, intentionally decrease your heart rate. I mean, that's autonomic control, right? And, and I think that's like, you know, the call to arms here,

you know? And I think that the side, the second and third order effect of that is, you know, when we can control our physiological state, we can control our attention. Yeah. And I think that's, that's the real power, right? In this world, right? Cause there is just the, the, the, the internet, the everything is just, it's designed, it's curated to take our attention. It's, it's robbing us of like our, our own compass for what we want to do in our life. You know, it's just, I, that's a whole nother discussion, but, um, but it's, it's, it's bang on. I'm totally in agreement with that. You have written the most beautiful article on your LinkedIn page

about attention. And I was reading all your, those LinkedIn articles today. They were really, really brilliant. And if we have time, which I suspect we won't today, we'll get into that. So I'll have to save that for a part two, if not. But I did say we're going to cover shift workers because I think that's important for people who've heard all this stuff. Are there any other behaviors that, you know, we've obviously, we mentioned sleep, wait time, eating windows, alcohol, caffeine, a bit of yoga, nidra. Before we get on to shift work, are there any other kind of behaviors you're really keen to share with people? Yeah. I mean, I think just leading into the conversation around shift workers, I think it's all relative, but I think a lot of folks have what they would perceive as really stressful lives,

right? So number one, you know, this is a study we just finished with our membership base. We had, I think, 19,000 folks participate. We're taking blood pressure readings over the course of three blood pressure readings over the course of three weeks. And then we asked them questions about their perception of their day and the reflection of their day. So did they perceive their day as threatening or did they perceive it as challenging? Okay. That was one question that we had a bunch of questions about sleep anxiety. But the threat and challenge was really interesting in that. So we're monitoring stress throughout the day. So we've got, again, an algorithm that is looking at heart rate variability, resting and heart rate, you know, 24-7. And the algorithm

basically maps it on a scale of kind of one to three. The higher in that zone, the higher stressed you are. And what was so interesting is that when people perceive their day as challenging, they end up in the higher stress zone. But what's so interesting is that and when they perceive it as threatening, they actually are less stressed. Wow. So there's some sort of paralyzing effect.

And what's even cooler is that there is a relationship between if you perceive it as threatening versus challenging, how that impacts your sleep and recovery next day. Wow. So the more challenging you perceive stress, the better you sleep and the better you wake up the next day. The more threatening you perceive your stress, the stress to be, the less well you sleep, the less recovered you are tomorrow. Is that to do with mindset and growth mindset, for example? Yeah, totally. Right. So and I think like, you know, I think a lot about like the model that I've been working off of for like the last two decades, you know, has mindset in it. But I think my point of view is that it's hard to just talk ourselves into a better future, right? When we're short-slept and

when we have circadian misalignment and when we don't have purpose and efficacy and control like these core psychological needs, you know, that we don't have an infrastructure to kind of think about those and support those needs, you know, our mindset is going to be compromised, right? So I think a lot of the models out there talk about mindset, but they forget how physiological and psychological influences actually show up in our mindset, right? I'm going to be much more capable of perceiving my day as challenging if I have a decent amount of sleep, if I have positive relationships in my life, if I feel like I have the skills and resources to take on the tasks in my day, I'm going to perceive the day

as more challenging, right? So it's way more complicated, right? There's a lot more variables, I think, happening or influencing mindset than I think a lot of the models that exist currently. I find them very, very deficient. Yeah, our physiology affects our psychology and our psychology also affects our physiology. I've been thinking about this for the last year. So I've been writing a book about some of this, right? Not quite through that lens, but this whole idea that, I don't know,

let's say you're at work and you receive an email from your boss. The state of your nervous system at that time will determine how you interpret that email, right? So if you're underslept, over-caffeinated, you're under-fueled, over-fueled, dehydrated, you can read that email as threatening. The boss wants to fire me. They're not happy with me. If you are calm and relaxed and everything's going well at home and you slept well, you're less likely to interpret as threatening. At the same time, I kind of feel that you can train yourself to not take offense, to not see that as threatening. Go, okay, that's

an email. That's just a neutral email. How I interpret it is up to me and how you interpret it then will affect your physiology. If you interpret it as threatening, then your heart rate's going up, your breathing rate's going up. So I don't know. I feel that you might be, we might be on similar pages with this, but this- No, we are. 100%. It's a two-way system, isn't it? It really is. And I think what the opportunity is, is that, and I said, oh, there's a lot of variables. There's really not that many variables. You know, like when I look at my model, I basically have, you know, if you have purpose, if you have self-efficacy and you have control and you're, you know, slept, you have appropriate sleep, circadian rhythms, and, you know, you're training

and you're working on your, you know, your fitness, like, it's really kind of those six things, right, that are going to impact your mindset. So your ability to kind of perceive the day, have optimism about the day and feel like, you know, you know, challenged by by the stress ahead is contingent on kind of these six things, right? And so when people are wondering, oh, why is my motivation all over the place? Why do I some days perceive things as stressful? Sometimes I perceive them as, you know, as threatening. Sometimes I perceive them as challenging. It's often because people don't have an infrastructure to think about purpose, right? Aligning their behaviors with what they say they care about, right? When that's off,

that dissonance is going to affect your mindset. Okay. Or, you know what? I don't have the skills and resources to do what is being asked of me today, right? That's going to throw off my mindset. I don't have control. I don't feel like I have autonomy over my day, right? And you can think about this in the context of kids too, right? Like when they feel like they don't have like a sense of control or autonomy or don't have the skills to do what mom and dad or teachers are asking of them, like stuff goes awry really, really fast, right? And that impacts mindset. But this is the stuff that I don't think

is really talked about in a coherent way. It's just, everything is really silent. And that's what I have. I struggle with the field of psychology and physiology. They're so siloed. And that's really, if I make any contribution to this world, like bringing these two things together in like a very coherent way is really my life's work, is what I want my life's work to be. I love it. Honestly, I absolutely love it.

They have to be brought together. They can't exist in isolation. Okay. Before I go down a rabbit hole there, which I so want to at the moment. I must deal with night shift workers because I said I wanted the start and I really don't want people leaving this feeling worried and scared, right? So, okay. I know, I know. You did a series of beautiful Instagram videos,

which I would direct people to if they want to know your views on this, right? Yes. One was, if you're on a series of night shifts, so I don't know, when I was a junior doctor, we would do seven nights in a row, for example. Right, right. You had some advice on how to stay on a night pattern. I wonder if you could share some of your top line recommendations there, please. Yeah. So if you are trying to stay on your nighttime shift pattern, you'll get home from your shift around, let's just say, 7 a.m.

And in the lead up, if you can, and again, this is the caveat is you need to be able to do this, all of these things I'm talking about as safely as possible, right? So in the lead up to your shift, so let's go back the other direction. So let's say you're let's go back the other direction. So let's say you're waking up at 3 p.m., 4 p.m. You want to try to get your as big a meal at that time as possible when you're still relatively primed, less insulin resistant. You want to try to, you know, eat as much food as you can during that time, because what you don't want to do is eat over the course of the nighttime. That's going to put extra stress on the system. So if you are eating during that time, eating really nutrient-dense food, stuff that is easily digestible, and then if you can like, you know, at the back end of your shift and what would be

kind of that morning timeframe, that would be ideal, right? Again, your body's kind of primed to, you know, metabolize and use those, those nutrients. Um, but again, I think it has to be low glycemic load because you don't want it to impact your sleep, which is going to, you know, you're going to need to sleep around seven, probably, you know, shortly after the end of your shift. So, and you want to try to, I think sleeping as close to the end of your shift is from what I've seen, what I've heard, and in the data that we have on frontline healthcare clinicians, that seems to be the best, the best situation to get, the best protocol to get in the most hours of sleep during the night and have the most restorative sleep. People who delay their sleep end up with much shorter sleep and

more fragmented sleep. Okay. So once you get back from, you know, once you try to minimize light in the lead up to bed. So sunglasses, hat, again, as safely as you can, because that light to the eye, again, is really gonna wake up the system. So a nice protein-rich meal just to make sure you're not hungry during sleep and you're kind of capitalizing on that moment where your body's kind of primed to metabolize food, get your protein, minimize light, and try to go to bed as soon as you can, once you get home from

your shift. Um, and then, uh, sleep, um, you know, try to get a consolidated sleep, you know, seven hours. And then when you wake up, work out, have a meal, be active, catch up with the family before you go on to your shift. And then once you're on your shift, you're doing your normal thing, stay hydrated. I think there's all sorts of types of shift workers, right? Manufacturing, not just frontline healthcare, but hospitals in general are really, really dry. I think it's like as dry as the Sahara Desert or something. It's like they're really dry. I think it's like as dry as the Sahara Desert or something. It's like they're super dry. So you want to drink a lot of water because that's another, that's like the

third thing that impacts sleep and recovery is dehydration. Right. So hold on, remind me, remind us of the first two. So you want to block light in the lead up to sleep, right? As much as possible to kind of signal to your body that it's time to sleep. If you need, you know, a high protein, easily digestible, you know, shake or whatever, just to get some extra calories before you sleep, you can do that. And then you want to try to sleep, you know, for seven hours minimum. So you don't want to get consolidated sleep. And then once you wake up, have a big meal, work out, visit with your family, whatever your setup is. And then that would be a time where you can have some caffeine. And again, you want to make sure you stop caffeine at least eight hours

before you intend to sleep. And that's another thing where people go wrong on night shift is they're having a lot of caffeine, which puts a lot of stress on the system. So if you're going to be sleeping at 8am, that means, let's say you're a hospital worker, at midnight, you don't want to be having caffeine, you know. But that is, it's just a vicious cycle, isn't it? Because if you need the caffeine to keep you awake to be alert, yeah. Creatine would be the other recommendation that I think I talk about in the post. But there's been some really interesting recent research looking at the impact of creatine and sleep deprivation. And that it's protective against the symptoms of sleep deprivation.

Wow. So there's something really powerful happening, creatine in the brain. And most people are probably a little creatine deficient. You can find it in foods, but I think especially people who are in, you know, these really demanding, you know, shift work type of jobs, they're, you know, oftentimes not able to get the meals on board that they need. So supplementation actually becomes really important for this population. So creatine is one that from the literature,

I would recommend. Okay, great. So we're using light, food, caffeine, exercise, and creatine to help manipulate the circadian rhythm so that you can stay on night shift. And most importantly, like decrease, like it's like you're trying to, it's stressful, right? So we don't want to layer that more stress on top, right? By, you know, this protocol that I outlined is going to minimize the stress on the system. Yeah. Right. Yeah. And how do you advise that people go from night shift back on to day shift then? Yeah. So, um, okay. So let's say you get home at seven o'clock. Um, this is a time where have a nice big breakfast. Um, do not have coffee or any caffeine. I'm going to tell you why that's really important in a second. Um, so, you know, have your, have your breakfast, um, get that big

bolus of light, okay. Sunshine, natural light, even if it's cloud covered, you know, have your breakfast, get that big bolus of light, okay? Sunshine, natural light, even if it's cloud covered, you know, get out for as long as you can, exercise, be active. You are going to start to have massive sleep pressure around 11 or 12, provided you didn't have caffeine, okay? That is the time where you want to just rush a nap, you know? And what's important is obviously you've been up all night, right?

So you're going to be very sleep deprived, but we want to try to protect your sleep that night. Okay. So we want to have a, you know, a 90 minute to three hour nap. You don't want to sleep more than that because again, you want to be able to fall asleep at night, but you're going to have a lot of sleep debt on board. So get that three-hour nap. Wake up.

Have a green tea. Some sort of caffeine, natural caffeine, if you can. And this is the time, do your errands. Be with your family. Get a nice dinner on board. And then when you naturally feel sleepy is when you want to succumb to that sleep pressure. And then aim to wake up the next day at the same time you saw light the previous morning. Okay. Okay.

Yeah. It's all there in those Instagram posts and you explained it really well. And I think there was enough there for people to at least take it on board and go, okay, these are things I can manipulate. And again, zooming out, it's this theme throughout this conversation that we have a circadian rhythm.

It's important as much as we can and some people are going to struggle for sure that we have a circadian rhythm. It's important as much as we can, and some people are going to struggle for sure, that we match those external behaviors to our internal circadian rhythms. We can use a variety of different things to do that. Light exposure, food, timing, exercise, hydration. Caffeine. Yeah. Actually, if you can learn to master this, you kind of become a master of your physiology because you understand how to manipulate it, right? Yeah, yeah.

I think that this is very much the path to mastery. Just even just learning and attention. And, you know, that's a whole other kind of discussion. But yeah, I mean, I think that this is really, it gives us the yeah, I mean, I think that this is really, it gives us the foundation, I think, to live our values with, you know, joy and energy. And I think that's kind of at a fundamental level, what we're all after, you know. I completely agree. Okay. Before we finish, Kristen, I must talk to you about the pros and cons of trackers. So I'll give you my perspective

to start off. Okay. So my perspective is that trackers can be useful to help us tune in to our internal physiology. For me, the goal has always been though, to not get dependent and overly reliant on trackers. I want them to teach me. So I do not have a Whoop band. Okay. So you obviously work for Whoop and the data you have accumulated is just phenomenal. I'm very interested in that data and what we can all learn from it. Are you able to make the case to me why I might benefit from wearing a woot strap? Well, I think having your baseline data is a pretty incredible source of insight in terms of how you're tracking, you know, and whether or not how you're living, how you're managing stress, you know, whether or not it's working for you. And I think you mentioned this earlier, you know, there's lots of subjective questions, you know, that we should be asking ourselves, you know, around what are my energy levels? Do I feel

alert when I want to feel alert? Do I feel sleepy when I want to feel sleepy? Am I attending to things that I care about? Am I able to control and direct my thoughts, right? Like these are questions that all humans should be asking of themselves, right? Because the answer to those questions is a direct comment on how likely how we're managing our physiology. I think where the data become really interesting is when there is that change in your life or you have, you know, maybe your period is becoming irregular and, um, you know, you want to try to triangulate and understand why that might be happening.

You know, am I entering perimenopause? I'm entering menopause. Like what, you know, so I think there's, or, um, you have, you're taking on more, more stress in your life and you, and you notice, wow, okay, it is actually impacting my sleep objectively. Now I know where to apply my effort. And I think at a baseline to answer your question, I want to know how to apply my effort. And I feel like Whoop is constantly kind of coaching me so I can show up as the best version of myself. It's helping me understand how to align my sleep-wake times. What is my sweet spot for the time I need to spend in bed? Just being able

to keep a check weekly. I'm not obsessing over my data, but I love that weekly readout where I can see, hey, my sleep debt's creeping up to an hour and 10 minutes. I know that, hey, 45 minutes is the sweet spot. That's where I stay bulletproof. I need to reorg this week to make sure that I'm kind of hitting that target. Oh, my sleep-wake variability is increasing. Wow, I'm up to almost an hour. I need to dial that in. You know, it just, it's hard to keep track of all that, right? There's a lot of cognitive load associated with just, you know, kind of knowing where we sit inside these metrics that ladder up to my ability to be the best version of myself. It's not a gazillion things, right? It's just a few things, right,

that I'm really paying attention to on the daily. Yeah, I can believe that for sure. And so if you're not in tune with your body at all, I can see a really powerful case to go, let me at least start understanding what's going on when I do this. When I have alcohol, oh my God, my sleep goes down. Okay, that could really help you change your behavior. Do you think someone could get obsessed and check it every day? And I'm not saying, look, I think it's, I always talk about blood pressure monitors because I've seen this for many years that about 50% of patients, okay, just a rough average, would thrive if they bought a home blood pressure monitor. They'd use it a few times a week. It would help them. Keep them in check. Keep them in check. Yeah. But the other half

would be obsessive with them. Check it three, four times a day. As soon as one- Like a CGM. I'd be like'd be like i was just like insane yeah and so what was what was fascinating for me is because that then you know we're all biased by our own experiences so i have a bias based upon what i saw with blood pressure monitors which are very different kinds of monitors i accept to go okay i think our personality probably plays a huge role as to whether we're going to obsess with this or use it as a tool for self-improvement. So on Whoop, because I'm interested in trying it, because I kind of think... You need to try it. I'd be so curious. Yeah, look, I'm open-minded to stuff. So I've tried lots of stuff. It's just I haven't tried that yet. And I'm sort of tempted to go,

okay, well, what am I going to learn? Is it something I can look at once a week and it not affect my day to day? Because I also like knowing what's going on with my physiology. So you're basically thinking I should try it. Well, I think the science is so good, you know, and the underlying data that informs our algorithms is just like, it's the best on the market. You know, it's like super high fidelity, you know, or obviously we're not, there's no watch. It's just literally collecting data. And I love that just from the standpoint of like attention. Like I don't want, well, that's interesting. It's coming on my wrist. Yeah. So that's interesting. So you can't

actually check it in real time. It's kind of, no, you have to go, you have to actively go into your app to see the data. So that's quite a nice way of making sure it doesn't take over people's lives. Yeah. And that's by design. Yeah. Yeah. Okay. It's, you know, it's not a watch. Do you see it as something that people could wear several times a year? Or do you think the benefit comes from wearing it 24 seven? I mean, I think there's so much benefit to just having it on, you know, like there's just so many cool insights. And of course, like I'm like, I love it, you know, because it's just, we keep evolving. We keep making it better.

Like our coaching gets better. You know, the AI is so fun. I work on the coaching aspect of the app, you know, because I was a coach for so many years. So that's like kind of like my jam. But yeah, I mean, I think just like, I just like people have different entry points, right? you know because i was a coach for so many years so that's like kind of like my jam but um yeah i mean i think just like i just like people have different entry points right like and what you need to focus on is different than me is different than the person on my left and right for the most

part but um but we all kind of have these fundamental things that we should be paying attention to which we've outlined in this discussion and you can track in whoop, which is cool. Right. And you can start to see the impact and, and four core, uh, core four of this paper, um, that hopefully we'll make it through peer review and be able to be out into the world. I, this is a great example of how four behaviors that we ran as a challenge. we ran as a challenge. Um, it was time-restricted eating, um, zone two cardio, uh, breath work and morning sunlight. Okay. Shifted people's circadian rhythms and improved cardiorespiratory

fitness and parasympathetic activity, like in ways that are just like kind of mind-blowing. And it was just like, you know, it was beautifully controlled. We had a match control. You know, we know their journal history. We know the folks that in the challenge that journaled these behaviors before. We know the folks that never journaled them.

We see the changes. It's just, so I think there's lots of opportunities to start to understand the impact of behaviors on these metrics that ladder up to healthspan, right? And to your longevity. So you start to be able to, I think for me, I've never been closer to my body. And I've never been, I never have understood my mind and body better than I do today. And I, and I honestly can say, I just would never have been able to do that without the

data. Yeah. It just puts, it's the, it puts the puzzle together for me. It's a wisdom accelerator. It like accelerates your wisdom. And I am so much smarter because I understand my body so much better. I know what a nice bath does and what, what hot does and how it affects me and what the right dose for me is. How much time I need to spend in bed, all this I would never have known. No, I love that. And if we had longer, which we don't today, I would absolutely be

jumping off there to be talking about how it's helped you tune into your intuition. But let's save that for a part two at some point, maybe not some of you in the UK or when I'm in America. I've thoroughly enjoyed my conversation with you today. I really have. I think you're, you're just, you're doing incredible work, honestly. And I love the way you communicate your ideas. For someone who's heard us today, Kristen, who is really struggling in their life and they just feel their health is not going the way that they want it to do. Let's say they can't afford Whoop or technology like that.

I know we've covered a lot today. What advice would you have for someone who feels that life's not going their way and they really want to break out of these patterns, but they don't know how? What would you say to them? I'd say, get off the phone, get outside, whatever you can spare, however much time you can spare outside, getting your, your, your eyes up, looking into the eyes of other humans, um, you know, looking at the trees and the birds. and i know we haven't talked about it today but you know like nature just has saved my life and i and i think that we are so disconnected from from like the natural beauty in the world.

And I think that's the place to start. And it's free. And I think just take time to, again, away from your phone, like to listen to your thoughts. And a lot of those thoughts are nonsense. Some of those thoughts are worth keeping. And a lot of those thoughts are nonsense. Some of those thoughts are worth keeping. But I think, you know, connecting to, really connecting and asking those questions of yourself of who you want to be and what are the things that you need to bring in your life so you can practice being that person. And maybe it's just, you know, increasing your patience and your tolerance and, you know, thinking about

how you are with your children. And I think those kinds of things, the things that are absolutely free and available to all of us is the place to start. And if you can get that right, a lot of other things in your life will start to fall into place.

Kristen, it's a beautiful answer. Thanks for all the work you're doing and thank you for coming on the show. Thanks for having me. It's been so fun. Really hope you enjoyed that conversation. Do think about one thing that you can take away and apply into your own life.

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