ZOE Science & Nutrition - Is exercise or nutrition more important for weight loss?

Episode Date: March 31, 2022

Our transformation into coach potatoes happened in the blink of an eye. Only 100 years ago, most people relied on manual work to make their living.  Today, things are different. Many of us live our lives in front of a screen. Online shopping and remote work mean some of us don’t need to leave the house at all. So how bad is this for us?  The answer is now clear: Low levels of physical activity lead to an increased risk of disease and a lower quality of life in older age. However, when we come to the question of what sort of exercise you should be doing, how often, and how much it contributes to weight loss, the answers might surprise you. In today’s episode, Jonathan speaks to a Human Physiologist to learn about the interactions between diet and exercise and their impact on human health: Dr. Javier Gonzalez is an associate professor of Human Physiology at the University of Bath and also a technical advisor to the athletes in the INEOS Tour de France cycling team. Download our FREE guide — Top 10 Tips to Live Healthier: https://zoe.com/freeguide Timecodes: 00:00 - Intro 02:00 - Episode start: quickfire round 03:45 - Why does exercise matter? 04:42 - How much exercise do you need to see health benefits?  05:40 - Defining exercise 08:16 - How much walking to do to see health benefits? 09:03 - What is cardio training & strength training? 10:41 - Differences between cardio and strength training 12:18 - Importance of strength training 15:28 - Is exercise or nutrition more important for weight loss? 18:03 - Dr. Javier’s research on fasting & exercise 22:16 - Should we exercise in a fasted state? 25:26 - Fasting and bone health 26:35 - What can we learn from professional athletes? 28:03 - How does glycogen get produced? 31:55 - How does exercise relate to gut health? 33:09 - What we should eat to benefit from exercise 35:40 - How to think about protein intake 37:26 - How should non-athletes think about food to complement their exercise 40:51 - Personalization & differences between men & women 43:57 - How important is exercising for menopausal women? 45:56 - Summary 51:42 - Goodbyes 51:53 - Outro Episode transcripts are available here. Follow Javier: https://twitter.com/gonzalez_jt Follow ZOE on Instagram: https://www.instagram.com/zoe/ This podcast was produced by Fascinate Productions.

Welcome to ZOE Science and Nutrition, where world-leading scientists explain how their research can improve your health. We've all heard the message, exercise is important. We should all go to the gym more often. If we want to lose weight, we need to exercise. But how much of this is true? In the context of human history, our transformation into couch potatoes happened in the blink of an eye. Our hunter-gatherer ancestors needed to venture out daily to find new sources of food. Only 100 years ago, most people relied on manual work to make their living.

Today, things are different. Many of us live our lives in front of a screen. Online shopping and remote work means some of us don't need to leave the house at all. So how bad is this for us? The answer is now clear. Low levels of physical activity leads to increased risk of disease and a lower quality of life in older age. However, when we come to the question of what sort of exercise you should be doing, how

often and how much it contributes to weight loss, the answers might surprise you. The fitness industry, like the diet industry, seems to present a brand new trend every month. So in today's episode, we'll find out what the latest science says, answering questions like how important is exercise for weight loss? Today's episode, we'll find out what the latest science says, answering questions like, how important is exercise for weight loss? Can fasting make exercise better for our health? And how much exercise do we really need to do to see the benefits? To answer these questions and more, I'm joined by Dr. Javier Gonzalez, Associate Professor

of Human Physiology at the University of Bath, whose research is focused on understanding the interactions between diet and exercise and how this impacts human health and disease. Javier is also a technical advisor to the athletes in the INEOS Tour de France cycling team. Javier, thank you for joining me today. So why don't we start with a quick fire round of questions from our listeners. Let's start with, is exercise the most important thing for weight loss? For most people, no. Okay, interesting. Does a walk count as exercise? It depends on how you define exercise, but

again, for most people, yes. If you're working out, do you need to eat lots of protein powder? No. Does too much cardio stop you from burning fat? No. Is exercise important during menopause? Yes. And exercise, I would argue, is always important. Fantastic. I love this question that we got on Instagram. Is yoga effective for weight loss? Probably not as effective as other forms of exercise, but it does have other benefits. Okay, brilliant. We should come back to that. And a related question. Do you need to be doing both weight lifting and cardio to get benefits from exercise? To get all of the potential benefits that exercise

can offer, then the answer is probably yes. Okay. And last question. Do men and women respond to exercise in the same way? No, but there's plenty more as well that influences that response that I'm sure we can get into. Brilliant. All right. Well, I think there will be quite a few answers there that will surprise many of our listeners and one or two that surprised me. But why don't we start at the beginning and then we'll sort of dig into all of this in more detail. Javier, why does exercise matter for health at all? At this point, we usually remind you about getting 10% off Zoe membership with the coupon code you can find in the show notes. Though I would love for you to do that, I'm actually here

to tell you about a common request we receive from people like you. It goes something like this. I've just discovered the show and now I listen each week, but I don't have time to go back and listen to all the previous episodes. Could you share some of the key things I need to know how to improve my health? The team has gone back through hours of recordings to find 10 of the most impactful tips led by science and put them into a free guide that you can download right now. To get yours, simply go to zoe.com slash free guide. So exercise is crucial for health, probably because we evolved in a environment where we needed to have a high level of physical activity. And nowadays, of course, most of us or a lot of us have jobs that are desk based and our lives are relatively sedentary. We end up doing less leisure time activity quite often as well and so we're not well adapted to that

environment that we're living in nowadays. An exercise has a number of benefits. It seems to affect almost every single tissue in the body. We commonly think of it improving perhaps our heart health, also our musculoskeletal health, the health of our muscles and our bones. But it seems like it even affects things like our fat tissue and our brains and almost every single tissue in the body is affected by exercise. And so how much exercise do you need to do to start to get those health benefits you're talking about? Yeah, the government guidance would be something like, it depends on which country, but at least in the UK, the government guidance is to do at least 150 minutes a week of moderate intensity exercise or 75 minutes per week of vigorous intensity exercise plus two strength sessions. Now that's an okay starting point for the general population but everything counts so as little as 10 minute bouts of any form of physical activity can start to accrue benefits and the general advice

is the more the better. So a very rough guide, and I'm sure different people will respond differently to exercise and some may enjoy certain forms of exercise. So in that scenario, I think the simplest advice would be do what you like and do as much of it as you enjoy doing. And is there a minimum amount at which this sort of starts? So, you know, if I just walk around the block really slowly, where does that start? Because those words you described, moderate exercise, like what does it mean, have you? Yeah, it's a great question because actually we should probably define what exercise is in terms of how that relates to physical activity. So physical activity encompasses every bodily movement that we make that increases the amount

of energy we're burning. And it doesn't actually have to include movement. So that's the textbook definition. I actually prefer the definition of muscle force production. And the reason I prefer that is because if you're sitting at your desk right now, the muscles around your torso are stabilizing that torso, your spine and everything. And that's got an energy cost to it. So you're expending more energy sitting upright than you would be lying down on the bed. And so that's already a form of physical activity, or at least an increase in energy expenditure. So any muscle force production, anytime your muscles are contracting, you're burning a bit more energy and that contributes to overall physical activity.

So I'm working out right now while sitting on my ass. Is that what you're telling me, Javier? Exactly. At the very lightest level, but yeah, you can feel good about yourself. I'm guessing that's not enough, though, to meet the criteria you were describing? No, no. And where exercise comes in, it's a bit of a funny definition because it really depends on your motivation. So if you go for a walk and that walk is part of a task, like you are walking to the shops, then it might not count as exercise. But if the intended purpose of your walk is to improve your health or fitness, then it comes under the definition of exercise. So I actually prefer the term physical activity to exercise because physiologically, that's what we're really interested in. It's all of the energy expenditure. And when we're talking about moderate intensity physical activity,

activities like brisk walking, starting to get your heart rate slightly elevated, but still able to hold a conversation. When we get into vigorous intensity, that's where you start and not be able to put a full sentence together without taking a breath. Got it. So that's like when I walk with my friends who are much taller than me, and I'm just trying to keep up. That's it. I like the idea of a brisk walk because it comes up actually in quite a few of these that actually that is the first level that might really make a difference to your health right which is a lower far than many people expect which is well if i'm not going into the gym pumping iron like none of this counts for how long would you need to do that to start to get some of the

health benefits that you were talking about with physical exercise yeah you can start to see some quite profound benefits actually with as little as 30 minutes of brisk walking per day. And that doesn't have to be all in one go. So you can split that up into five or 10 minute bouts across the day and accumulate it over the day that can actually start to improve things like your blood lipid levels, levels of fat in the blood. So that's pretty amazing. So you're saying that 30 minutes a day of brisk walk actually can make a profound difference to like measurable markers in our blood and that we don't even have to do it all at once. You're actually saying, you know, I could cheat and do that in

three or four different pieces. Exactly. Exactly. That sounds quite counter to what I think many of us would imagine. Let me come on to the related question that a lot of people were asking us to discuss before this, which is this idea of cardio versus sort of strength training or weightlifting. And firstly, could you just explain what those things are? Because they're words that we hear, and I think many of us aren't really clear exactly what they mean. And then explain, like, why is there this difference? And does it matter for people thinking about this for their health and probably their weight as well? Yeah, sure. So when we're talking about cardio, I guess most of the time we're talking about, well,

at least in the scientific area, we would probably call it endurance exercise. I guess the term cardio comes from the idea that most of the adaptations you get are in the cardiovascular system. And these are things right from the lowest intensity of brisk walking through to running, cycling, swimming, and that kind of thing, where you might do an exercise session that lasts for 30 minutes up to an hour. You get some athletes doing very long training sessions of four or five hours of this type of exercise, then strength training might be doing weights in the gym, where you are lifting weights, maybe from five to 10 repetitions and repeating that in sets. It doesn't have to

necessarily be lifting weights. Strength training does also include body weight exercises. So it could be things like squats, so body weight squats, things like press-ups and pull-ups. But even actually for people who are slightly advanced in age, even just getting up and down from a chair a number of times can be a form of strength training that can help improve their capacity for daily living, really. And what's the difference? Because you talked about the time, but what's going on physiologically that differentiates these? And then can you explain a bit what impact that has and why it matters? Sure so they do sit

on a spectrum so you can get areas that slightly overlap and you can probably envisage that if you think of something like cycling up a hill a very steep hill there's a point where that probably turns into more of a strength workout on your legs than it does a cardio workout so the force of you pressing down on the pedals crosses over into that strength workout and flip it the other way around where you might be doing a circuit class in a gym session you might be using weights but it's relatively light weights and you're lifting a lot of reps and that can transition into a cardio workout. However if we go to the extremes of cardio versus strength then they do have quite different adaptations and that's why the advice would be that to get all of the health benefits of exercise it's good to do both cardio

and strength work and the cardio exercise will improve things like your cardiovascular system so your heart can get stronger your blood vessels become more compliant or more elastic if you like so they can help lower your blood pressure whereas with strength training you get a number of other adaptations so your muscles clearly can get stronger but even your ligaments and tendons can get stronger. And I guess one of the things that people often don't think about is bone health. Heavy strength training can improve your bone mineral density and so improve the strength of your bones also. I think maybe just to talk about that second bit, this is one of the reasons why strength training is not just for people who are like in their twenties and look amazing on Instagram,

right? There's some real health linkages. Could you talk for a minute more about that? Because I think often we think about strength training perhaps has been very much about sort of the body beautiful, but there's more to it, right? Absolutely. So our strength will typically peak when we're about 30 to 35, maybe 40 for some of us, if we're lucky, and then it will gradually decline after that point, almost no matter what we do. However, by doing strength training, we can slow that decline. And the aim is that there'll be a certain point where we gradually just become weaker as we get older. And there'll be a point where even getting out of a chair or lifting the shopping bags is now becoming too difficult. We're not strong enough to do that.

And so the idea is if we can maintain strength training, we can delay the point at which getting out of a chair is now impossible to do alone. So it becomes really important for healthy aging, not only from that strength standpoint, but also then the bone health. So if we do have a fall, then we're less likely to fracture the bone because the bone has a greater bone mineral density. Got it. And what's going on between these two? So there's obviously stuff going on at a very physiological level, which is quite different between this cardio exercise, which you're talking about going on for a long time, and this sort of strength training where I'm just doing

this in a very short period of time. Can you help us understand a little bit more about what's going on, how that ties, I guess, to our energy system, because I think that's going to start to bring us through to nutrition, which obviously we're very interested here at ZOE. Yeah, sure. So it's probably worth starting with strength training. So things that are very short duration, they're almost like mini bouts of exercise and the energy we use there and then extend to the longer duration exercise. So with strength training, when you initially do a very high intensity movement, let's say you lift a weight with your bicep. The main energy system you're probably using there is something called the phosphocreatine system. system and that's commonly why people who lift a lot of weights sometimes supplement with creatine

because that can increase the creatine stores in the muscle and that can help that energy system so they can do more repetitions without fatiguing but that doesn't really use the fuels in the same way that longer duration exercise does so when you increase to longer duration exercise, one of the benefits of cardio is that you're burning through energy. And the main fuels that we use there are carbohydrates and fats. So one of the other differences between cardio and strength training is that with cardio, we're going to be burning through total energy, more than strength training on the whole. And we're going to be burning through our carbohydrate and fat stores. In addition to that, we get a high heart rate that's maintained over a long period of time. There's greater blood flow through all of the circulatory system. And that's

why we get those adaptations in blood vessels as well. Because our body sort of has to improve the way in which it can get this energy to these muscles that are working away. Exactly that. Yeah. You know, I think one of the biggest questions that we all ask, which is, is exercise or nutrition more important? So if you were to ask me weight maintenance, I would answer very differently. For weight loss, for most people, diet is almost certainly more important than exercise. And I guess just to validate that, for most people, it's a lot easier to eat energy than it is to burn energy.

So as an example, a typical one hour gym session for an average person might be about 400, maybe 500 kilocalories of energy. Now my bowl of porridge in the morning or oatmeal is easily over 500 kilocalories of energy and so in a small bowl you can easily overeat what you've may have just burnt in the gym. Now we should also remember that our resting metabolic rate is constantly going on. So we're constantly burning a baseline level of energy. So we shouldn't try to always offset what we burn through exercise. But clearly, exercise doesn't make a big dent in our energy budget, compared to how easy it is to eat those calories. Now, it is very different with elite athletes that we can maybe come on to later, but for the vast majority of people, that's the general finding. Which I think is really interesting, right? And it's quite counter to, I think, a lot of the messaging that we've heard over the last 30 or 40 years, some of which I think comes from very large food companies that

have a particular angle to deliver there, where I think the story we're told is, you know what, everything to do with weight is because people aren't doing enough exercise. And, you know, if only people were doing more exercise, it'd be fine. And therefore, you know, it's fine to sell sugary drinks in schools is my favorite example of this to kids, you know, as long as there's a playground, because after all, they could just go and burn this off. And I think what you're saying is, obviously, exercise is really important, but you can't just go and do a bit of exercise to burn off eating all of this incredibly poor quality food that we're all surrounded by now in the developed world. Exactly. I guess the way I would frame it is probably that exercise has a number of benefits,

but we shouldn't expect that just by beginning exercise, we will lose weight. It can actually help control appetite and it can help with things like body composition, but that's when in conjunction with diet. So really, yeah, diet comes first, but exercise can really help us achieve the goals that diet is achieving as well. Now you're doing some really fascinating research actually about interaction between fasting and exercise, right? Which also I think really challenges this idea that a calorie is just a calorie and that a good diet is about making sure that the number of calories in equals the calories out. Can you tell us a bit about this research that you've been

doing and what it tells us? Yeah, sure. So we've done a series of studies now and we're continuing this line of work. And with the short term studies where we study people for about 24 hours, we might ask them to skip breakfast or eat breakfast and exercise or rest. And we tend to find that when they skip breakfast and exercise, they burn more fat during that that when they skip breakfast and exercise they burn more fat during that bout of exercise and that's been known for quite a long time we tend to burn about 20% more fat when we're fasted in that overnight fasting state compared to say an oatmeal based breakfast. Our work tried to understand then if that continues over a full training program, because what we would see

in a 24 hour period might be very different over a six or 12 week timeframe. So one of my former PhD students ran a pretty intense study where he fully supervised every single exercise session. He recruited 30 men to complete this six-week training program, and he measured the amount of fat and carbohydrate they were burning every 15 minutes of every single training session over a full six weeks. And we did see with the very first session, the group who were performing that exercise in a fasted state were burning almost double the amount of fat actually in this study compared to those who were performing the exercise in a fed state. Those lines were parallel throughout the six weeks of training so as people became fitter they were all burning more fat but the group who were in the fasted state was still burning more fat at the end of the training program than the group in the fed state. Now this links into that idea that it's more than just calories, because we did actually give both groups the same number of total calories before

and after the session. So the only difference was the timing in which they consume those calories. So whilst one group was burning more fat, both groups had the same energy balance, and so they had the same weight loss throughout the whole study. So for weight loss, it seems to be more about energy balance than it does to be about fat burning or fat use, but for other health outcomes, that's where it became really interesting. So we found that the people who were burning more fat

actually improved things like their glucose control and their insulin sensitivity to a greater extent than the group who had breakfast before exercise and weren't burning through their fat stores. So what you're saying is actually they were getting the same number of calories, but some of these people were exercising fasting, and somehow this is changing the way their body was working. And you were seeing these measurable and sort of clinically important improvements in these health markets that you would expect to, you know, have an impact on their long term health, because their body was getting better at burning fat than burning blood sugar. Is that the right way to understand that? Yeah, yeah, we think it's something to do with the turnover of fat stores within probably within

muscle. So if you think of our fat stores we store most of our fat in fat tissue but we also have these small fat droplets within our muscle an important fuel store within the muscle but what we find is in people who are sedentary these pools of fat in their muscle you can almost think of them as stagnant pools and you get buildup of toxic metabolites. And they seem to interfere with the muscles ability to respond to insulin and to take up glucose out of the circulation, take up sugar out of bloodstream. And what we think is going on here is that by performing exercise in a fasted state, you burn those pools in the muscle, they're

turning over more quickly, they're not as stagnant. You don't get that buildup of toxic metabolites. And so the muscle is healthier. It can take up more sugar out of the bloodstream more effectively. And so does that mean we should all be doing all of our exercise in a fasted state? Does it just mean that, you know, when I take my daughter to school and push her for 30 minutes, it feels like a brisk walk, she's getting heavier, then at least I should do that before I have breakfast. How do I think about applying this? And how should our listeners think about applying that to their lives? Yeah, it definitely depends on what your particular goal is, and might even depend on you as an individual. So I should caveat that we have only currently run this study

in men, in middle-aged men, and we are keen to do this study in a wider population, including women as well. But the other thing to consider is what your goal is. So if, for example, you want to do an important session, you want to work hard in your session or as hard as possible, then actually having a breakfast is a good thing because your performance will be impaired if you haven't had a breakfast. And that's even if your exercise session is in the evening. So there have been studies where people either ate or skipped breakfast in the morning. They all had lunch at lunchtime, but their performance in the evening was still impaired when they had skipped breakfast in the morning. So my advice for the kind of average person would actually be to mix it up. So to perhaps do two or three sessions a week where you might perform them in a fasted state and other

sessions in a fed state. And everything in biology and physiology is about trade-offs. There are actually potential downsides to performing exercise in a fasted state as well. And if I'm listening to this and I'm not only thinking about health improvements, which is obviously incredibly important, but I'm also thinking about weight loss, how do I understand that? Because you said, hey, I'm now burning fat. People are like, well, that's good. I want to burn some fat. But then you also said actually, because what you actually saw was not a change in weight loss between these groups, because you fed them exactly the same amount of food, which is a bit artificial, I guess, compared to what they might do naturally. How do people think about this

for weight loss? Do you have the data yet? Or is that also part of the future studies? Yeah, that's part of our future studies. From our short term studies, it seems like if you don't force people to eat what they had skipped before exercise, then actually over 24 hours, they don't fully compensate for having done their exercise in a fasted state. And so if that continues over the long term, then they may lose more weight. But yeah, I'd be very hesitant to say that because we know that longer term of exercise on appetite are very different to the short term. So we hope to have that answer in know that longer term of exercise on appetite are very different to the short term. So we hope to have that answer in a year or two's time.

Well, we'll be excited to talk about it. And as you know, this is an area we're really interested in helping to support as well. So I think the playback here, I think, is doing some exercise in a fasted state can be really beneficial for health. And I'm hearing you say potentially also from what you've seen supported for weight loss, but that that is not really proven by the data yet. Because as we know, you can do these 24 hour studies, and then you translate that into three months, and suddenly, you know, these effects get balanced out, which is part of why this science around everything to do with nutrition and exercise is so complicated, right? Yeah, absolutely. And I think it's probably worth just mentioning as well, if people are going to

try this exercise in a fasted state, especially people who are perhaps concerned over their bone health, it might be worth taking some calcium before those sessions. Because one of the downsides to that type of exercise is it's probably a catabolic state for the bone. Javier, what does that mean? So the bone is in a state of breakdown. Okay, doesn't sound good. No. And it's probably because when we exercise, we sweat out salts, as we might be aware of, but we also actually sweat out calcium as well. But it has been shown that taking some calcium before a bout of exercise

in a fasted state can help prevent some of that bone breakdown. So for certain populations, I would advise taking some calcium before those sessions to try and prevent that. The show you're listening to right now that's providing you the latest evidence-based health and nutrition information from the world's top scientists, well, making it takes a lot of time. We think it's well worth it, all in the name of improving your health. All we ask in return is this, send a link to this podcast to someone you think would benefit. And if you haven't already, click follow this podcast wherever you're listening right now. Okay, let's get back to the show. And if I'm doing a brisk walk, am I worrying about that even? Or is that more like a more

energetic activity than you're describing than that? Yeah, you're probably okay with a brisk walk. But this is probably more relevant for athletes doing this type of training more vigorously. Yeah. Bringing up professional athletes, I think is a great way to talk about your work with, I think some of the most amazing athletes in the world, right? Professional cyclists. And I know that you work with the INEOS Tour de France team. They seem like almost a different species of person than I am. Is there anything that you do there that you think is relevant for ordinary people listening to this call? And indeed, also, what is really different? So how do we learn from this for those of us who are not these super athletes? Yeah, I think you're absolutely right. They are

completely different species in many ways. There are some things we can certainly learn from them. And actually, the idea of performing exercise in a fasted state really stems from professional sports, running and cycling in particular, where these athletes would do exercise sessions, not just in a fasted state, but they would train twice a day. So their first session would really deplete their carbohydrate stores. They would then eat low carbohydrate at lunch and maybe do another session in the afternoon. And so they're really pushing the limit on, they're almost taking that fasted exercise to the next level. And the idea behind that is that one of the stimuli to adapt

to exercise is a low glycogen concentration in muscle. And what that is, is it's our storage form of carbohydrate. So when we store carbohydrate in our muscle, it's in this form of glycogen. So Javier, right, because we talk a lot about blood sugar, right? So when we eat carbohydrate, like rice or bread or Coca-Cola or whatever, right,

it turns into this blood sugar. Just help us to understand then, so how does the glycogen fit with that? Sure. So the blood sugar or glucose in the blood will be taken up by muscle during exercise that happens independent from the hormone insulin. But when we're at rest, we have a meal, we get an insulin response

and that insulin will help drive that sugar into the muscle. Once it's into the muscle, it has two fates, if you like. One will either be it'll be burned as a fuel, and the other will be that it will be converted into glycogen. So that's where it's stored in its kind of fuel tank, if you like, within the muscle. Got it. And you said there's a limited amount of this that's in the muscle. Could you explain that for a minute? And that ties in, I guess, to what you're describing with these super athletes. Sure. So whereas our fat stores are, for all intents and purposes, limitless, we could just run for days and days and days on our fat stores, our glycogen stores will run out very quickly.

And it's actually why people often term it hitting the wall during a marathon, where after about 90 minutes or so of vigorous intensity exercise, those glycogen stores will be pretty much completely depleted. And we have to really drop the intensity. I think I hit the wall quite a bit sooner, have you? But yes. So yeah, it will run out very quickly. And when that glycogen is low, that seems to be a signal that starts a cascade of events in muscle that stimulates some adaptations. So the kind of idea behind training in this depleted state was that you're ramping up the volume on that signal to adapt. So it really stemmed from

professional athletes and it's now starting to filter into the health area. Got it. So these people, they're saying, I'm using up all of that glycogen, I'm continuing to exercise hard, I've got to find other ways to create energy. And that can't just be the blood sugar you're saying, because they're intentionally not eating meals with, you know, they're not drinking sort of sugary drinks to keep this going. So they're presumably having to get to burn fat. Is that what they end up having to do? Yes, exactly. Yeah. And so they're burning fat in that state. And the downside to burning fat as a fuel is that it's a relatively slow burning fuel. So you can think of it as kind of a diesel fuel, whereas our carbohydrates are a petrol. And so you do have to lower the exercise intensity when you're burning fat as a fuel. So

it's more the kind of low intensity endurance sessions that they might do this type of work with. And you're creating sort of flexibility then, are you? Like I've got this ability to run on both these fuels and that's a good thing, is it? That's the ultimate goal, yeah. Because especially athletes, they do need to be able to burn fat as a fuel when appropriate. So at those low intensities, but they still need to be able to burn fat as a fuel when appropriate, so at those low intensities, but they still need to be able to burn carbohydrate as a fuel. When the race really gets going, they need to sprint up a hill or sprint to the finish line. That's a carbohydrate dependent activity. And it's where different modes of training and nutrition can really adapt that metabolic flexibility.

Some strategies that have been used in the past influence one of those, but you lose the flexibility of the other. So one example of that is actually low carbohydrate, high fat diets. When they're eaten chronically in the longer term, then you do increase the ability to burn fat as a fuel very effectively but it seems like the ability to burn carbohydrates as a fuel is down regulated even once your glycogen stores are full again so even though you've got that carbohydrate in the muscle you're not able to use it your body has adapted to using fat all of the enzymes for carbohydrate are down regulated and so you just can't tap into that energy when you need to do we know about how gut health fits into any of these discussions around exercise?

Have there been any studies that look at these links? And is there anything you can share with us there? Yeah, I think it's a really exciting area. I think we don't know very much about it at the moment. What we do know is that if you just compare athletes with non-athletes then they do have very different gut microbiome profiles it's difficult to disentangle whether that is an effective exercise or an effective diet because most athletes are burning a lot of energy and eating a lot of energy so the total volume of food is very high but also the composition tends to differ as well from non-athletes. So it might be higher protein, potentially higher carbohydrate as well. And because of that higher volume of food, they're probably also getting more total fiber, more prebiotics as well. And so there's a number

of reasons that could account for differences in the gut microbiome between athletes and non-athletes. I think the next step would really be to do randomized controlled trials of exercise to see how that directly affects the gut microbiome, ideally with and without weight loss. So you can then disentangle the effects of exercise from weight loss. Whenever we're thinking about exercise, then I think we get a lot of questions about what should we eat sort of before, during, and after exercise. And I think we get a lot of questions about what should we eat sort of before, during and after exercise. And I think there's a lot of myths here, right? You already answered right at the beginning. Do I need to have a protein shake if I'm doing exercise? And I think you gave a pretty strong no. So could you tell us a bit about what are the facts about sort of the

requirements? And we don't always believe a lot about this idea of sort of macronutrients and so because there's so many different sorts of foods, but help us to understand what are the facts about sort of the requirements? And we don't always believe a lot about this idea of sort of macronutrients and so on, because there's so many different sorts of foods, but help us understand what are the realities of this? Yeah, well, one of the main roles of protein, or one of the reasons for taking protein, or at least eating protein in conjunction with exercise is to facilitate muscle reconditioning. And what I mean by that is the adaptation of muscle. So muscle is mainly comprised of protein. And we often think of the contractile protein. So the part of the muscle that produces force, the part that gives it the size and the bulk that you see in a bodybuilder. But actually, the proteins are also involved in the enzymes within muscle, the mitochondria within muscle,

which are the kind of powerhouses of the muscle that produce the energy for cardio exercise. And so protein is important in remodeling all of those different aspects of muscle. So I stand by the point that you don't need protein powders. Protein itself is certainly important for both people who exercise and people who don't exercise the reason i said no to protein powders is because you can achieve the same goal with dietary food sources of protein and in many ways they can actually be more effective than certain protein powders so just to validate that if you you compare, for example, a control condition where they might not have any protein at all versus soy-based protein versus whey,

then what you tend to find over a training program, same amount of training, that people will gain more muscle mass with the whey versus the soy and more muscle mass with the soy versus nothing. But what's really interesting is they had a fourth condition in this particular study that I'm referring to, and it was milk. So just plain milk and it performed just as effectively as whey protein. Amazing. So you don't have to eat something super artificial. You could just, and I'm not suggesting everyone should eat milk because it's a big variation we see in response, but that's sort of quite amazing. And how much protein do you need? Because I think this is also an area where anywhere you go on like the grocery stores or anything now, here's this ultra processed bar

with a big label on it saying like high in protein, which obviously makes me think, oh, well that's good. I have that. And I have heard people say, oh, you must eat some vast amount of protein within 30 seconds of doing exercise or all that hard work is wasted, which I think if you're like me and you don't really love exercise, you're doing it because it's important for your health. It's like, oh my God, I'm going to have wasted all that hard work if I don't get this protein in 30 seconds. I've always been a bit sceptical, but I bet there's real data on this, Javier. How do we think about that? Yeah. So I guess before I tackle the dose point, I'll just talk about the timing point where it's

one of those things where there's a grain of truth, but it's taken completely out of proportion, where immediately after exercise, we are more sensitised to protein. And so if, for example, you have a pint of milk, which has about 20 grams of protein in, in the hours after exercise, more of that protein will be incorporated into your muscle than it would do if you hadn't exercised. And it's still a relatively small amount. So of that 20 grams, it tends to be about two grams have been incorporated, so about 10%. So exercise does sensitize the muscle, but that doesn't completely drop away within 30 minutes. It just gradually comes down over about 48 hours. So even 24 hours after exercise, your muscle is still sensitized to protein intake more than it would be if you hadn't exercised. It's just

slightly less than it would have done immediately after exercise. So rather than a window, it's just a gradual decline in that sensitivity over a full 48 hours. And so if I'm thinking, you know, I'm a listener, I'm listening to this, does that mean I should be worrying about this? Or actually, if I'm eating a good balanced meal with like plenty of plants, which we know have lots of different protein in them, and I'm not a super cyclist, am I going to get everything I need? Or is there something I need to adjust to sort of compensate for? Yeah, if you're eating three or more meals a day, you're probably eating close enough proximity to your last exercise bout that you're getting

a benefit. So you probably don't have to worry about it. If you're going to have exercise and not eat for 10 hours, then yeah, you probably want to fit some protein in between. Got it. So if you're doing sort of quite very time restricted eating, for example, I guess that would be a good example of one of the sort of sustainable dietary patterns then potentially thinking about how exercise fits with that time window is something that given what you're saying it sounds like you don't want it 12 hours away from when you eat equally well it sounds like sometimes you might want to do the exercise before you eat and other times you might want to be doing this shortly afterwards etc exactly and there may actually be a case here for,

there might be some scenarios, I'm not completely against supplements, for example, I think they have a place and it might be here where someone might be performing time restricted feeding or intermittent fasting and not want to eat a lot of calories and a supplemental form of protein can then provide the protein without many calories. And so there's probably a scenario there where they can be useful. And I think the other scenario is for convenience as well. So yeah, I'm not completely against them. I just think you can achieve most of the goals, almost all of the goals with real food.

Brilliant. And I think often the challenge is you can have a window thinking just about the exercise, but when you step back and look at the overall health impact, then we know so much now about the importance of the quality of overall food. So I think figuring that out is interesting. Now, I have a question here, which is actually the reverse of this. How do I best fall for endurance exercise? So if I am doing some of this extreme exercise that we're talking about, how does that change this advice if at all yeah and this would definitely depend on the level of the athlete here so if you take

the tour de france cyclists what you see in their diet would be viewed as pretty horrendous by most people in terms of the amount of sugar for example that's in it because they are burning through so much energy and sugar is such a good fuel for high intensity, prolonged exercise that the amount of sugar Tour de France athletes get through is actually incredible. So some of the reports in some studies have been up to half a kilo a day of pure sugar, which is incredible. Which I imagine you're not telling us to copy at home, kids. Is that right? Absolutely not. This is one scenario where we treat them as a different species because in an hour, they can burn through almost 2000 kilocalories of energy, whereas your average person might be burning through 400. So it's just a completely different

ballpark. I'm guessing that all these muscles I'm using right now to keep my body upright while talking to you is not getting me to the 2000 calorie output. Unfortunately not. Okay. That's really helpful advice. So one of the things we touched on at the beginning and which I'd really like to sort of talk about here at the end is personalization and differences. And I think you already said that you see differences between men and women, but that there were also other differences. Would you mind talking a bit more about that? I think both in general and then I think we'd love to talk a bit more specifically one of these big changes that we see with women is obviously sort of before menopause, perimenopause, after menopause. What does the science say and how should people think about that depending upon where they are as an individual? Yeah, I think it's a great question.

It's one that commonly comes up when I give talks actually is should women do their exercise differently to men, especially with this theme of whether they should exercise before or after eating. And there's a bit of confusion as well, because I think in some TV programs that have been shown over here, at least, it was suggested that women respond very differently to men. And it's true that women tend to burn more fat than men during exercise. So when we control for all of the important factors, and we compare men and women, women tend to be able to burn about 13% more fat than men. But that's actually relatively small, that difference, compared to other factors. So if, for example, we look just within the group of men or within the

group of women, then the difference between the highest and the lowest person is more than 300% difference. So there are greater differences between individuals within each sex than there are between the sexes. So we've done work on this, and we're keen to do more work on it. The next step is to understand what are the factors that determine why one individual can burn a lot of fat versus another. And sex is probably one of those factors, but it's probably not a big one. So I guess rather than a fat oxidation gender gap, it's more of a gender overlap in that regard. If we extend that to, say, the menopause, then it does link because one of the main reasons we

think women can burn more fat than men is the hormonal status of women. So estrogen, amazingly, they have done the studies where they've given men estrogen and immediately their fat oxidation increases. And it probably also depends on the number of receptors women have to estrogen. So the estrogen is a hormone that will stimulate a variety of responses, but it can only stimulate those responses when it binds to its receptor. And we've actually found that women with more of the receptors for estrogen show the higher rate of fat oxidation.

So there's this complex interplay between the hormone, but also other aspects of physiology of the person to actually get a response there. So that's sort of the science showing you all these differences. If you're listening to this, trying to figure out what to do, and maybe let's take that example as a woman is I think a great example, which is something that we end up talking a lot about, right? Which is that your body is changing and what worked for you when you were 35 may be different. And this is true for men as well, but it's particularly true we see with women because of this really big change around menopause. What should they be doing? How important

is exercise around menopause when one of the side effects we often see is weight loss? But I think there's also other implications you touched on, I think, earlier to do with sort of bone density. How do we think about both exercise and diet, I guess, together through this period? Yeah, those are the points I would most focus on in people who are considering how to mitigate the effects of menopause. And with the kind of strength loss and potential loss of bone mineral density, it's where strength training really comes into play so ideally lifting relatively heavy weights or it can be running as well so you get a reasonable impact when you run much more than cycling the forces that go through the ground when you hit that ground and through your leg and foot

also stimulate bone growth and tendon strengthening so combining either weight training and or running with diet can really be the key there. So on the dietary front, it's probably four main areas I'd consider. One is calcium. So are you getting enough calcium in your diet? The second is vitamin D, which I know in America, in the US, quite a lot of foods are fortified. In the UK, not so much. So you might need to take a supplement there, especially if you don't live in a sunny climate.

The third would be omega-3s. So making sure you eat plenty of oily fish to get your omega-3. And the fourth would be adequate protein intake, because we often actually forget that a lot of bone is actually comprised of protein as well. And when we eat protein, one of the hormones that is released, it's known as GLP-1, that also stimulates bone growth as well. So those four dietary factors combined with some form of exercise that is going to load the bone is probably crucial there. I think that's really fantastic and very actionable advice. I would like to maybe

just sort of summarize what's been a very wide ranging conversation and where I think there's many things that we haven't really had a chance to get into. So I look forward to hopefully coming back to this in the future. I guess the starting point is this really rather surprising fact that exercise is not the key to weight loss. It's very important for your health, but actually on its own is not really going to transform your weight loss. That actually exercise starts at a lower level than I think many of us imagine. So apparently I can do a brisk walk. And I think you said 30 minutes a day was really going to have an impact on my health. And I didn't even have to do this all in one go. So I could actually have maybe like three pieces, which I think, again, is not at all what I think many of

us understood. You then explain there's actually two sorts of exercise and that this strength exercise, which is very different from this longer term cardio, are both important. That the longer term exercise, which I guess is your brisk walk through to running or cycling is great for our cardiovascular system and our blood pressure and trying to deal with heart disease. But actually strength exercises is very important. And if we want to stay strong long term, and that can even mean so that we can continue to get in and out of a chair and things like this, then actually we need to do that because

you painted this slightly depressing story that I think from about 35, we're all getting weaker and weaker. And that therefore, we sort of have to fight against it because most of us are doing what I'm doing right now, which is sitting on a chair talking. And the good news is that apparently that burns some calories because I'm using some muscles, but it's not really enough to get me out of that chair in the future. Is that right, Javier? That's correct. Yeah. Good summary. And then I think we talked about this amazing studies that you have been doing and that you

are recruiting for the next stage of looking at the impact of fasting on health. And I think this very counterintuitive discovery that actually, you know, doing exercise while fasted can actually improve some of your health outcomes. And that for most of us, the answer isn't to only do this fasted exercise, but actually a combination. And I think in general, one of your stories here is actually a sort of variation is important. And this flexibility of your body is very important. You taught us a bit about glycogen and why people hit the wall when they do the marathon. And that there's a lot of stuff that professional cyclists do for fun that we probably don't want to do at home. That as a result, they have these amazing gut bacteria, these different microbiome. And we think there's something really interesting,

but this is really an area that is still very early. And then we talked about the food that you need to eat if you're exercising. We understood that actually our muscles are mainly made of protein, which I guess explains why people talk about protein all the time, that we do need it. It's not just a marketing myth created by big food companies, but that actually there have been clinical studies where they've shown that if you drink a pint of milk, that works just as well as a fancy powder. And that although there is some scientific truth around this idea that in the hour after exercise, you're going to incorporate even more protein. Actually, if you're not a professional athlete, if you're eating three meals a day and that those are sort

of balanced meals with probably whole foods and proteins, you're fine. If you are doing something like time-restricted eating and you ended up with a very long period between exercise and food, then actually potentially you should think again about that and either maybe adjust a bit or even think about supplementing, for example, with calcium. And then I think we finished with this fascinating stuff about personalization where you said it's true that women on average burn, I think you said 13% more fat than men, which sounds like a really big difference. It's related to estrogen. But when you go and look within the differences within women, for example, you're seeing this

300% variation, which is very similar to some of the things that we've seen in some of the big Missouri Predict studies looking at inflammation and things. So there's this huge variation within individuals. And so a one size fits all guide is going to have the same problems as everywhere else. But this does mean that as you go through menopause, there's a big change because of the change in hormones. And that there's really some very specific things I think that you recommended. And let me see if I've got that right. So firstly, you're going to be losing strength, you're going to be losing bone

mineral density. So you really need to think about that in addition to thinking about how your diet might need to shift because of the weight gain that may go with this. And so I think you're pushing, you know, particularly here quite strongly that you need to think about strength conditioning. Can you be lifting quite heavy weights? Because I think you were explaining they need to be quite heavy to have that impact. That interestingly, actually running is a form of strength conditioning, which I think will be a surprise for many people. And that on diet, you had some very specific recommendations. So calcium, are you getting enough? Vitamin D, omega-3. And for people who are not vegan, then actually dairy-based products were a good solution

there. And if you're not vegetarian, then sort of oily fish in terms of omega-3. And then addition, making sure you're having adequate protein intake, where again, you said, you don't need to be doing some sort of special shake. It's about understanding that you're eating a sort of balanced meal that's got lots of protein. Yep. Javier, that's an amazing sort of tour across all of these things. I think that's really fantastic, sort of actionable takeaways. Javier, thank you so much. I think that was so interesting. We enjoyed it very much and look forward to having you back in the future

with the results of those new studies. My pleasure. Thanks for having me. Thank you to Javier for having me. 10% off your personalized nutrition program. Finally, if this episode left you with questions, please send them in on Instagram or Facebook to Zoe, and we will try to answer them in a future episode. As always, I'm your host, Jonathan Wolfe. Zoe's Science and Nutrition is produced by Fascinate Productions with support from Sharon Fedder here at Zoe. See you next time.