ZOE Science & Nutrition - Most replayed moment: The surprising science of weight loss | Alan Aragon & Professor Sarah Berry

Episode Date: July 28, 2026

Today we’re talking about fat loss. For decades, we’ve been chasing the perfect weight loss diet. From Atkins to carnivore, countless trends have promised remarkable results, yet fail the test of time. So how do we cut through the noise and find a formula that actually works? In this episode, I’m joined by nutrition researcher Alan Aragon and Professor Sarah Berry to unpack the science behind sustainable fat loss, and explain why, in some cases, the first step toward losing weight might actually involve gaining a little first. 🌱 Try our science-backed and tasty wholefood supplement Daily30 Get our brand-new app and Gut Health Test designed by world-leading gut health and nutrition scientists to build healthy eating habits 👉 Join ZOE Follow ZOE on Instagram. 📚Books by our ZOE Scientists The Food For Life Cookbook Every Body Should Know This by Dr Federica Amati Food For Life by Prof. Tim Spector Ferment by Prof. Tim Spector Good Mood Food (preorder) by Prof. Tim Spector Free resources from ZOE The Hormone Harmony Guide: Tuning Your Body’s Internal Orchestra Eating for Better Brain Health: Your brain-gut blueprint How to eat in 2026 - Discover ZOE’s 8 nutrition principles for long-term health Live Healthier: Top 10 Tips From ZOE Science & Nutrition Gut Guide - For a Healthier Microbiome in Weeks  Better Breakfast Guide Have feedback or a topic you'd like us to cover? Let us know here. Episode transcripts are available here.

Hello and welcome to Zoe Recap, where each week we find the best bits from one of our podcast episodes to help you improve your health. Today we're talking about fat loss. For decades, we've been chasing the perfect weight loss diet. From Atkins to carnivore, countless trends have promised remarkable results, yet failed the test of time. So how do we cut through the noise and find a formula that actually works? In this episode, I'm joined by nutrition researcher Alan Aragon and Professor Sarah Berry, to unpack the science behind sustainable fat loss. And explain why in some cases,

the first step towards losing weight might actually involve gaining a little first. Alan, why are we becoming more overweight? It's a combination of several things. So the way that I see it, it is a gradual shift towards sedentary living. And this has been facilitated by labor-saving devices, and even electronic and digital means to not even have to get up off the couch to prepare food,

you just make a call and then wait for it to show up at the door and that's it. In addition to that, there's a fundamental misunderstanding of how to maintain healthy body weight. And people simply don't know or are unaware that fundamentally, in order to lose weight, you have to impose a net caloric deficit over a period of time. And so when people are not aware of that, then they easily believe that there are magic foods that, for example, burn belly fat or magic foods that burn fat and then other foods that you should completely vilify or avoid. And that's where a lot of the confusion comes in.

And in addition to that, I would say that in the present time, people have a greater tendency to use food to, I guess, medicate. or entertain themselves, just from general work, stress, interpersonal stress, anxiety. And so food ends up being kind of used as that sort of tool. I think that the combination of those things is at least some of the factors underlying the obesity phenomenon that has basically started in the early-ish 80s and continued on to today. To add to what Alan said, I do think as well as the fact that we're more serious,

as well as we're all living such different lives and we have all of this food noise, our food landscape and the food choices that most people are making now are so, so different to 20, 30, 40, 50 years ago. And they're almost hijacking our system. You know, we have evolved to be able to handle excursions in blood sugar to handle fat, to handle all sorts of things that are thrown against us. But we haven't evolved to handle the food landscape that's out there that's evolving even more quickly than science can evolve. Maybe we can imagine a new client, Alan. So let's say they're in midlife, they want to lose, say, 10 pounds.

Where do you start? And could you take us through the journey with them sort of step by step? Okay, so not everybody is ready to go on a program where they transform their body. Okay, let's say somebody thinks they're ready. I would start with, let's see your sleeping cycle. How much sleep are you getting? Do you feel it's enough? And what is your history with regard to that? Because sleep is the X factor for a lot of the success or failure in programs. Because when you don't get enough sleep, not only does it kind of affect the obvious stuff,

meaning your energy to be physically active and certainly your energy to engage in any kind of progressive training program, but it also increases your appetite in your cravings, your hunger levels. and increases your cravings for calorie-dense, hyper-palatable foods. That's what sleep-deprived people mostly reach for almost instinctively. There's some very interesting research showing that subjects who are sleep-deprived consume across studies, on average, about 200 to 300 calories more per day while they're sleep-deprived. There's studies where they actually take people into these kind of chambers,

and they monitor them for weeks and they actually sleep deprived them. They say, right, you're going to become a short sleeper, so less than six hours. And they see anywhere between 150, 300 calories per day increase in how many calories they're having just from depriving. I mean, it's a pretty cool study that these guys do. Yeah, and the interesting thing is it went the other way too. They took a group of habitual less than six and a half hour sleepers. and they put them through a coaching and training, sort of this education program on how to improve their sleep hygiene,

and the goal was to add two hours of sleep a night. So they wanted to bring them up to, I believe, eight and a half hours or so. Seven hours of sleep appears to be this sort of threshold where, you know, below that, it's, you know, the outcomes are somewhat adverse. So they trained these folks to bring their sleep average from less than six and a half hours up to eight and a half, and they ended up eating about 260-ish, 270-ish calories less per day, which is pretty dang significant in the scheme of things, especially when you consider that while they were sleep deprived,

they probably had some sort of compromise in the amount of energy output that they had through either the exercise pathways or the non-exercise pathways, just lower spontaneous physical activity and less capacity for purposeful physical activity. So that's the sort of the basis of everything. Get the sleep, right? And also, so by changing the sleep, it changes the types of foods that you're having.

We did a study at King's called the Slumber Study, which was one of those sleep extension studies where people who were short sleepers less than six hours of sleep were asked to increase by two hours, exactly similar to the study you're saying. And what we saw was that by people increasing their sleep, they had no advice about what food to have at all. All they were told was, here's good sleep hygiene, we want you to increase your sleep. And we happen as part of this to be measuring the kind of food you're having.

They significantly reduced by quite a large amount, the amount of sugar intake that they had. So this deficit in calories is coming from the bad foods as well. So we are in this sort of perfect storm where we're surrounded by all this terrible processed food and we've got these incredibly addictive phones, you know, with TikTok and Instagram, whatever, keeping us up late at night so we sleep less and then we need to eat more processed food. So there's a sort of, we are surrounded by this environment that is attacking us, aren't we? Oh, yeah. Bidirectional badness, basically.

Yes. So you fixed my sleep. What happens next? Right. So fix the sleep. And then the other elements we're to try to simplify this is, okay, so you have a goal of fat loss. You have to make the individual understand that this is about fat loss. And the scale is just a very, very vague proxy of what's going on.

And so the usefulness of what the bathroom scale is telling you will get progressively less. So it'll get more and more useless, the more fit that you become and the closer you come to your goal. Why is that? Some people can actually gain lean mass or muscle mass while they're losing fat mass. And so they're losing inches. Their body fat percent is coming down. But the scale won't necessarily register that. And so people have to understand it's not 100 percent about the scale telling you what's going on.

I'll give you an example. So if you were to take somebody through who is completely untrained, they're fresh off the couch, and their goal is to reduce their body fat in half. In that process, they may gain, depending on the time period, let's say it's a six-month period. They may gain up to six, probably more pounds of muscle mass during that period. And I would rather people look, when they engage a program, I would rather them look at the six to 12 month overview rather than, you know, the popular, okay, I want this in six weeks type of thing. And so if they understand that they're going to gain a certain amount of muscle mass just by virtue of engaging the right training program and getting their diet correct, then this is going to offset, who knows, six to 10 pounds, of weight loss that they would have wanted.

And in that case, that's where it becomes important for people to take note of how clothing is fitting. You know, take note of how that might reflect circumference measurements. If you have more fancy devices for guesstimating body fat percent like the in-body or dexia bod pod, any number of these devices, then that gives you a little bigger picture than what the scale is saying. But let's imagine that somebody just, you know, they don't want to wrap tape around themselves and they don't have necessarily access or they don't want to go over to get their body comp done at some facility. Well, then you would want to limit your weekly weight loss to, I'd say a maximum of 1% of your total body weight per week at max. If you lose more than that, then there's this tendency that you're sacrificing too much lean mass while you're losing fat mass.

And so that would be the other sort of simple thing. We got the sleep. We've got the rate of weight loss. You want to limit it to half a percent to a full percent. And really, the one pound per week benchmark is fair. It's fair and it's realistic. Now with that said, I don't think people should be discouraged if they're losing even half of that. So if you're losing half a pound a week, two pounds a month, you know, heck, that's still 24 or 25 pounds in a year.

And most people have spent the last 10, 20 years putting on that 25 pounds. And so people have to have these realistic expectations of weight loss. So I would say half a pound to a pound a week is a good rate of expectations. expectation. If you lose more than that, then that's a bonus. And then finally, from just sort of a programming standpoint, okay, we got the sleep, we got the rate of weight loss, and we've got protein. Most of the focus that my colleagues and I have been on research-wise, has been on protein. So I have certainly a biased interest in protein. So the amount of protein that people consume per day that is optimal has been a matter of debate without overcomplicating

it. In the general public, 1.2 to 1.6 grams per kilogram of body weight is a fair and realistic protein target for the general population. But I think that that is just kind of a good starting point. I really think you start getting into optimal and helpful for fat loss and lean mass preservation once you get to the 1.6 grams per kilogram of body weight and imperial terms that's 0.7 grams per pound. If you fall somewhere between 1.2 on the low end, I'd rather see people do 1.6 all the way up to 2.2 grams per kilogram of body weight. So about 0.7 to 1 whole gram per pound of body weight is really sort of the sweet spot for the goal of weight loss or fat loss.

Exercise is similar to food in the sense that you have to find the type of exercise that you actually enjoy and even look forward to. That's the way to get compliance. So as we get older, we just lose our functional capability muscularly because we just sit around and barely move. And for people who have really no clue as to how to engage like any sort of resistance training program, then you can just think of three basic movements in any variation of the planes. Push, pull, squat. those three movements.

If you can engage those through a progressive amount of volume over time, and you become familiar with how to apply effort to various movements within a simple pull, push, and squat type of thing, then there are ways to do full-body training sessions. There are ways to do split sessions where you might do up. body one day, the next day you do lower body and then you repeat that cycle again through the week. And then you have other splits yet where you're doing some variation of either the three times full body or the upper lower split plus some specialization on a lagging body part. So that's some of the basics of it. I think that's ways you can fit it into your lifestyle without it feeling

daunting as well. I'm someone that's never like to exercise. I've never been to a gym. I play a bit of tennis, but other than that, the thought of doing any kind of exercise class fills me with horror, so I'm just not going to do it. So I've started doing what I call exercise snacks because I am sitting at my desk all day. I am now 48. I do need to be thinking of not how I look, but my muscles, the fact that I know I'm at that age, they're all going downhill. And so I have by my desk one of those exercise band. So I do what Alan says every now and then. You might see me on calls going like this. And squats, every time I boil a kettle, I do squats. I can get 20 squats in. I have about eight cups of tea a day. That's 80 squats without even thinking about it. I'll end this episode with something

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