ZOE Science & Nutrition - Recap: Why you should stop counting calories | Giles Yeo

Episode Date: December 23, 2025

Calories. They’ve been at the heart of dieting advice for decades. Eat fewer, burn more, lose weight. simple, right? Except it’s not that simple. Calories only tell us a fraction of the story. To really understand what's going on, we need to take a step back and look at the bigger picture. Helping us take this step is biologist Giles Yeo. He’ll explain why obsessing over the numbers doesn’t work, and how we can change the way we approach weight loss. 🌱 Try our new plant based wholefood supplement - Daily30+ *Naturally high in copper which contributes to normal energy yielding metabolism and the normal function of the immune system 📚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 Free resources from ZOE 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 Listen to the full episode 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. Calories. They've been at the heart of dieting advice for decades. Eat fewer, burn more, lose weight. Simple, right? Except it's not that simple. Calories only tell us a fraction of the story. To really understand what's going on, we need to take a step back and look at the bigger picture. Helping us take this step is biologist Giles Yo. He'll explain why obsessing over the numbers doesn't work and how we can change the way we approach weight loss. Everybody knows that you need to count your calories. There's a certain number of calories that you're supposed to eat.

And as long as you eat less than that, you'll lose weight. And if you eat like one calorie more than that, you'll put on weight. and we're living in this world where, like, counting calories is the way that we understand what happens and the calorie number is what determines our way. It's not correct if you deal with it the way we do today. In order to lose weight, you need to eat less.

Let's just even want to debunk anything because that's got to be true, okay? You need an energy deficit in your food if you want to lose weight. And there is no if, ands and buts about that because it's a function of physics. So in other words, if you now have a meal, let's call it a balanced meal, whatever you might actually look at. And if you then suddenly took that meal and says, well, instead of eating all of it, I'm going to eat two thirds of it or half of it in a balanced way in which I'm going to half the carrots and half the steak and half the potatoes and actually eat that, then ultimately, yes, you will lose weight.

So if you calorie count in a perfectly balanced way, yeah, you can actually, you can and you will lose weight. the issue is that is not the way life functions. And people begin to sort of take it to extremes and sort of worship the calorie and use the calorie as the only piece of information there. Because ultimately, I think in order to lose weight, you need to continue eating a balanced diet, but eat less of it. The problem with calorie counting is it takes away the nuance of it and you start to just count the calorie. And a calorie does tell you how much food. that is there, but that is all it tells you. It is completely nutrient blind. It doesn't tell you how much fat is in there. It doesn't tell you about sugar content, about fiber, about salt, about anything. Anything about that either makes the food taste good or bad or is good for you or not so good for you, the calorie cannot tell you any of that information.

So I think we need to, I guess, my point here is that the calorie is one-dimensional, Literally is one-dimensional when you're referring to a meal. What's the reality that happens then for people who are following calorie counting? Because I think, again, a lot of people are listening to that, well, surely if you do follow calorie counting, then you will lose weight. And, you know, the only reason it doesn't work is because you've got poor willpower and you can't stick with it. And therefore, it's all, you know, it's all your own fault. And I've, you know, that was definitely what I grew up with. So does counting calories work?

I mean, so imagine if you were saying that you're in some diet, whatever the diet is, and this particular diet prescribes that you only have 300 calories for lunch, just as an example, these diets exist. Now, if you therefore walk into a store because you're working or what have you, and you purely look at that, well, then in theory, you could buy 300 calories of a chocolate bar or 300 calories of a salad or 300 calories of a ready meal or whatever or 300 calories of soda. Okay. And if you do that and think about it, well, then it does make a difference what you're eating.

And the calorie counting is just a really not a very smart thing to do because you can say, well, I did have 300 calories. I just consumed it or less soda, which is slightly extreme, but not that extreme, because people do to decide that that's the amount of calories I'm eating, particularly if you're putting it, plugging it into your app. And so in that sense, it is not very useful because you could be having more calories but eating something different. Carrots, steak, something else compared to drinking 300 calories of a soda and it makes a big

difference. So I think because of the one dimensionality of the calorie, it is not very useful. And if you're focused just on one number and you're looking at the back and you're seeing that number, then that's all you'll focus on. It's easier, I grant you. but it's, I would argue that it's very, very meaningless. I think what we want to do is improve the quality of our food. Even as we eat less, we need to eat less, yes, but actually eat less, but probably

eat better quality food. The calorie is a completely useless number. And, Giles, is this just like your opinion or is there any actual science behind what you're talking about? There is science behind it. I mean, I didn't make this up. I didn't, you know, invent it and, you know, and called it the yo diet or anything like that, it is true. Because, okay, people say, yeah, but all calories are equal.

They are, once they're in you as a little poof of energy, poof. And I think ultimately we have to remember, okay, the mantra, let's go with a mantra. This mantra, you can say is from me. We eat food, we do not eat calories. Okay. And depending on what we eat, our body has to work harder or less hard to extract the calories from the food. Sweet corn is an example where clearly we can eat 100 calories of sweet corn, but we don't absorb anywhere close to 100 calories of sweet corn. Then our body extracts the calories from the food. And depending what you eat,

you can extract differing amounts of energy from the foods we actually eat. So I think you were saying something that, you know, I've heard often on this podcast and from others that the body weight is not as simple as just sort of calories in versus energy out. And maybe it would be if we were like some sort of simple machine.

but we're not, we're human beings. Our system is a lot more complex. What are the key things to know about how our body manages weight? And I think a lot of people listening to this will be immediately thinking about appetite because, of course, there's been all of this noise in the last couple of years about these new drugs that have this amazing impact on appetite that seem to have nothing to do with calorie counting and seem to be achieving like outcomes that, it seems sort of impossible, I would say, until a couple of years ago.

So what's actually going on inside us, Charles, and how do we know that? Let me just stress again, we do need to go into energy deficit to lose weight. And that's because it's physics. It's a function of physics. How you get there really depends on who you are. You know, clearly there is an energy balance equation, and that is true. The complexity is not in the physics of it. The complexity is, because that's the how, how you get to where you are.

The complexity in terms of weight loss, weight maintenance, is in no why. So why do some people eat more than others, for example, or why do some people appear to be more efficient with their food in terms of burning versus storage versus how fast you would actually burn the food? Let me give you an example. Why do some people stop eating when they're stressed, like work stress or what have you,

whereas other people start eating when they're stressed? So, for example, I'm a comfort eater. If I'm stressed, suddenly I'm, you know, my face is in a bowl, noodles. I don't want to back myself into a stereotype, but that's what I do. My wife, however, is someone who the moment she's stressed at my work or something like that, she's going, I have no appetite. It's literally diametrically opposite, but it's the same hormone that goes up, the stress hormone, cortisol goes up, but yet we behave entirely differently. That is just one behavior and the world is split into those who eat after stress and those who don't eat after

stress. So that's an example of the why, right? Other people, people, why do some people appear to be hungrier than others all the time? And, you know, or how come some people take more to get full? And these are not imagined behaviors. They're just, they're just not. Okay. Where, yes, clearly they're going to be cultural, sociological underpinnings about why, where, how much, and what we eat, clearly. But there are also huge biological underpinnings driving our appetite, driving what we eat, driving who we like to eat with, driving, you know, where, when, all these things. And all of that integrates eventually into some form of energy excess or energy deficits. And so you either gain weight or lose weight

depending on these innate drives, myriad of different reasons about why you end up eating more or eating or eating less. It's really interesting. I never thought about the idea that, you know, some people might be a comforty to and some people might turn off. I think if I'm really stressed, I often want to eat less, actually. Yeah, exactly. It says, oh, that dude, don't even talk about food. Whereas I do eat. I'll sit there.

And it comforts me. And so I know, I know that I do it. And you try and, you know, organize your life so you don't do it, but sometimes you just do it. Could you tell us a bit about the science of appetite? Because one of the things I'm really struck, you know, with my journey with Zoe over the last eight years, is that I ate a completely typical, like, British or American diet eight years ago. And one of the interesting things, you know, having followed sort of my diet now for, for quite a few years, is that it feels as though my appetite has changed a lot and that I don't have the same level of, I don't quite know

how to even describe it, like sudden hunger bursts in the same way. But what's going on there, Charles. So appetite is an interesting term because it's actually quite a, we sort of understand it, we talk about appetite, but it's actually quite a complex concept because it's an integrated concept. What I mean by this? In my head, I simplify appetite into sort of a triangle, okay, of which there are three points. One is hunger. So how hungry do you feel? I think we understand what that means. One is how full are you. Now, that is not the same thing. Okay, how hungry you and how full you are, are different circuits within the brain and the reward elements of food. How nice or lovely does the food taste to you. Now, those three all speak to each other. They're not

mutually exclusive and they involve different parts of the brain. And if you tug on one side of the triangle, the shape of the triangle changes, correct? And so in other words, if you are more hungry, for example, you're going to take more food to get fooled up. And if you're more hungry, the food has to be less rewarding for you to enjoy the food. If you're really, really, really starving, a bit of bread, a bit of cheese, a bit of rice, okay? It's like the simplest foods are the best. If you are not hungry, suddenly the rewarding element of the food has to be really, really big for you to continue eating. It is the concept of the dessert tummy, where why, after a full meal, you're never going to order another steak after a meal or whatever it is

you're eating, but chocolate comes and you eat it. my son has explained that he's got a separate, you know, ice cream stomach for the last decade. Yes, and he's right. He's right, is he? Where is it in? He thinks it's in his legs, or at least when he was six he did. I think now, I mean, he's 16, I think he probably isn't there. Where is his dessert stomach and how does that work?

So the dessert stomach is this integrated concept where the fuller you are, okay, the more rewarding the food has to be. So let me give you an example from an evolutionary perspective, okay? Take the grizzly bear, okay, Pacific Northwest, you know, Oregon, in the Washington area, hitting the salmon run, preparing for hibernation. And just to be clear, the salmon run isn't like a running race or a ski race. The salmon run is... Is when the salmon are swimming up the river in order to disboring their spawning grounds, and the grizzlies know this, and so they kind of park themselves in between the spawning ground

and where the salmon are coming and eat the salmon. at the beginning of the salmon run the bear eats the whole salmon down to the bone okay just eats it and you can see it's just a whole pile of bones but as the bear gets fuller and fuller and fatter and fatter because he's trying to gain fat the bear only eats the skin of the salmon and the fat underneath the skin of the salmon

why? Because this is calorically wise calorie wise or even though they don't count is the densest part of the fish and you can do this and this is what the bear does because he is trying to make sure that he can continue stuffing he or she is trying to continue to stuff as many calories into his body as possible even when he's now completely full of salmon. So he's like eating the really fatty bits because that doesn't take up as much space

with your calories you were talking about before. So it's like bear chocolate. It's bear chocolate. Now clearly desserts are a human-specific cultural underpinning. so the bear is not having dessert. But this concept of which the fuller we become, the more dense the food we want to eat before we actually will bother doing it,

before it tickles the reward parts of it, is a conserved thing. So this is not a human, your dessert tummy is not a human-specific thing. It is a conserved behavior. So it's got to be high in energy density, okay? And so what are foods that are naturally, so in other words, that for every given gram of food you eat,

you get more energy in it, So what are those? Those are going to be foods that are high in sugar, free sugars, or high in fat. And what are foods that are high in sugar and fat, their desserts? And so that primarily is the big driver. So fatty foods or sugary foods, you know, 50,000 years ago on the savannah, you know, we're not going to be eating a tart or citron and a muscat, but it might be honey. It could be really ripe fruit. It could be making sure you eat the fat bit of your steak or bison or venison or whatever.

is you're actually eating. Today, it's a tart or citron. But the whole thing is you're looking for something high in fat and high in sugar so that you can continue stuffing food into all the nooks and crannies even after you've eaten 2,000 calories with a venison. I'll end this recap with something I think you'll like, a free gut health guide created by our team of scientists here at Zoe. Many of us aren't sure how to best support our gut. So we developed an easy-to-follow guide, complete with tips, recipes and shopping lists, designed to help you look after your gut. The guide is delivered straight to your inbox, along with ongoing nutrition insights from Zoe,

the Science and Nutrition Company on a mission to transform the health of millions. To get your free gut health guide, just visit zoe.com slash gut guide. Thanks for listening. You know,