The Diary Of A CEO with Steven Bartlett
Moment 209: The Real Reason You’re Gaining Weight (Even If You’re Exercising!)
Fri, 18 Apr 2025
Tried everything to lose weight and nothing’s working? It’s not your fault. According to geneticist Giles Yeo, your body is hardwired to hold onto fat—especially as you age. Yeo breaks down why your metabolism slows, how your genes shape your hunger, and why exercise isn’t the fat-loss fix you think it is. If you’ve been eating better, moving more, and still not seeing results… this is the science-backed reality check you’ve been waiting for. Listen to the full episode here - Spotify - https://g2ul0.app.link/y96HFbLIDSb Apple - https://g2ul0.app.link/9Ow3Z5SIDSb Watch the Episodes On YouTube - https://www.youtube.com/c/%20TheDiaryOfACEO/videos Giles Yeo - Why Calories Don’t Count - https://bit.ly/3XWPtaL Gene Eating - https://bit.ly/3Yc37X6 Learn more about your ad choices. Visit megaphone.fm/adchoices
Chapter 1: How do genetic differences affect weight and eating habits?
With my genetic makeup, how might there be differences in my genetic makeup that make my relationship with food and eating and weight loss different from yours?
Oh, okay. I probably don't have as good an answer. Genetics does not have as good an answer about why different people eat differently, aside from cultural differences at the moment. So the genetics. The reason behind that is because it's very difficult to accurately determine what someone has eaten in order to do genetics.
What we do know, because we can actually observe, is how people of different ethnicities are susceptible to different diseases. So famously, East Asian people, people that look like me, South Asian people, Indian, Pakistanis, Bangladeshis, cannot get as large BMI-wise, before becoming at risk of type 2 diabetes, right?
Compared to white people, Polynesians famously, who can get pretty large before they actually end up getting diseases. So that's a classic example where this is why South Asian people, East Asian people have a higher predisposition of diabetes, even though... obesity is not particularly a big thing in their cultures. But then you then begin to look at body shape. That does matter as well.
Where do you put your fat? Do you tend to put the fat on your bum, on your tummy? How tall are you? How short are you? And all of these things, which we can see visually, we can see, there are people who are then susceptible or not susceptible to specific diseases. Other things you can't see.
Why are African-Americans, for example, more likely to end up with cardiovascular heart disease, less likely with diabetes, whereas why are Indians more? And so you then begin to ask the question, and there we have genetics.
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Chapter 2: What is the 'obese gene' and how does it influence body weight?
What about in terms of this obese gene? I read in chapter two of your book that there is a gene for obesity.
There are more than a thousand genes for body weight. The obese gene in chapter two, which I talk about, is this leptin gene, is this gene which lets your brain know how much fat you have. Ah. So that's the exact gene. Leptin is the gene that I'm talking about in chapter two with the obese. It's called the obese gene because the mouse was called obese.
There was a lack of imagination because the mouse was a naturally occurring mouse that had a mutation in the same gene. Scientists found out what that was and then found out that it was conserved in humans. And that's where my boss, Steve O'Reilly, then came in and found that that gene was also mutated in some humans. So that's the obese gene.
It's the fat gene, fat gene, meaning gene from fat, that lets your brain know how much fat you have.
And is that possible to be not just on or off, but slightly defective? So some people can just get... a little bit more hungry than others? Or is it a binary thing where it can be on or off?
So leptin, for whatever odd reason, is pretty much binary. So if you have a little bit of it, you're fine. If you have none of it, you're not. However, there is obviously a pathway. Leptin signals to the brain, which signals to something else. And there is another gene that I looked at called MC4R. It's part of the pathway. It's is a rheostat. It's like a thermostat.
And so, for example, we have found thousands of different mutations in this gene. And you can imagine that depending on the severity of the dysfunction, some are completely dead, some are 70% functional, we can predict how much someone will eat in a test buffet meal scenario if they have a 50% functioning gene versus a zero functioning gene. And we now know that 0.3% in this country at least.
So 200,000 people in the UK, a million people in the United States will carry mutations in this MC4R gene, making them more likely to end up with obesity. So that at 18 years old, if you carry a mutation in this MC4R gene, you are on average... 18 kilos heavier, 40 pounds heavier at 18 years old on average. And that's 200,000 people in this country. So it's not super common, right?
It's still 99.7% of the people's body weight's not determined by this. But there are a lot of people's body weights who are dependent on this specific gene. But it is a tunable system. So it's a little bit or a lot means that you're either slightly heavier or a lot heavier.
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Chapter 3: Can genetics determine how hard it is to change your body weight?
And you begin to lose muscle mass. So all of those things put together means that you inexorably become larger. Then what happens at 60 years old, your metabolism then starts to drop as well. And then you get even larger middle-aged spread, et cetera.
So on that point about the more muscles you have, the higher your metabolism. That means if I've got big muscles, then I'm burning my food faster. Yes. Fantastic news. I'm going to work out later. Lift some weights. Because I was really startled by that. After I read it in your book about... us gaining more and more weight as we age, I googled it.
And the Healthcare Research and Quality Agency said that we naturally tend to gain weight as we age to the tune of one to two pounds per year, according to their review. And that's from the Agency for Healthcare Research and Quality. which I found quite startling.
But completely accurate. So the numbers, so what the numbers that we have is, yeah, I think that's right, actually. So between 20 and 50 years old, those 30 years intervening, the average person, average, will gain about 15 kilos in weight, which is 32 point, yes, two pounds a year, one to two pounds a year. 15 kilos in weight is gained over 30 years on average.
Some gain very little, others gain a hell of a lot more. We look at ourselves in a mirror. I look at myself in a mirror, but it's true. I don't want to be that guy. Yeah.
Mate, I don't know how much choice you have. What can I do to try and stay? Because for me, it's not really about the weight thing or how you look. It's more about like, I don't know how to say this. There was this big set of stairs the other day. Really, really long set of stairs leading down to this lake. I was in Indonesia a couple of months ago.
And I remember thinking about those stairs and thinking, God, if I wasn't, you know, athletic and strong and didn't have good knees and things like that. There's no way I'd be able to get down this long winding hand carved set of Indonesian stairs so that I could go on this boat trip that I was going to go on. And I just thought about how It was a weird thing.
I know this is kind of a strange story to tell, but it crossed my mind. I got to the bottom of the stairs and I turned to the person I was with and was literally like, you know, that's why I've got to stay in shape for as long as I can, because I want to do these boat trips and I want to go on this little rafting thing.
But I won't even be able to access it unless I can go down up and down those stairs, like 200 meters of stairs down this cliff. So that's what I care about. I care about being active and strong and fit for as long as I possibly can. And from what you said about gravity and weight, being overweight is going to inhibit my chances of being able to do those stairs.
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Chapter 4: Why do people tend to gain weight as they age?
It is so, so, so related, independent of weight, you know, from there. So muscle mass is the most important for healthy aging the moment you get 60, 70 plus.
Interesting. Okay, so I'll keep doing resistance training.
Correct. Always keep resistance training. And lifting weights as long as I can. Lifting weights as long as you can. At some point, you won't be able to lift weights. Well, I don't know. Don't write me off.
Yeah.
That's the naivety of youth. Yeah, you just assume you'll always be able to do what you can do now. Yeah, it's something I think a lot about. And I think a lot of people will watch this podcast because... probably, especially this time of year, we're in January, they'll probably be trying to find ways that they can cut fat. They want to be a bit skinnier.
You said, I think you said half a stone you want to lose. I'm in the same place. I think most people want to lose a half a stone or something. What is the way that you would suggest to do that? The simple way, you know, not the like complicated, go buy this guy's course and do 3 million sit-ups, whatever. The simple advice you would give someone that's hoping to create sort of sustainable,
Weight loss.
16%.
And there's a sweet spot. So if you eat too much... and you're not lifting, you're stressing your kidneys because your kidneys have to get rid of the nitrogen from the protein, okay? So 16% is a sweet spot, and it doesn't mean steaks only. It can mean beans, tofu, any kind of protein from anywhere, 16%. Second is fiber. We need to eat as much fiber as physically possible, okay?
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Chapter 5: How does muscle mass impact metabolism and weight management?
Chapter 6: What role does lifestyle play in weight gain despite genetics?
It is so, so, so related, independent of weight, you know, from there. So muscle mass is the most important for healthy aging the moment you get 60, 70 plus.
Interesting. Okay, so I'll keep doing resistance training.
Correct. Always keep resistance training. And lifting weights as long as I can. Lifting weights as long as you can. At some point, you won't be able to lift weights. Well, I don't know. Don't write me off.
Yeah.
That's the naivety of youth. Yeah, you just assume you'll always be able to do what you can do now. Yeah, it's something I think a lot about. And I think a lot of people will watch this podcast because... probably, especially this time of year, we're in January, they'll probably be trying to find ways that they can cut fat. They want to be a bit skinnier.
You said, I think you said half a stone you want to lose. I'm in the same place. I think most people want to lose a half a stone or something. What is the way that you would suggest to do that? The simple way, you know, not the like complicated, go buy this guy's course and do 3 million sit-ups, whatever. The simple advice you would give someone that's hoping to create sort of sustainable,
Weight loss.
16%.
And there's a sweet spot. So if you eat too much... and you're not lifting, you're stressing your kidneys because your kidneys have to get rid of the nitrogen from the protein, okay? So 16% is a sweet spot, and it doesn't mean steaks only. It can mean beans, tofu, any kind of protein from anywhere, 16%. Second is fiber. We need to eat as much fiber as physically possible, okay?
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