'I was taken by a senior colleague to some fancy schmancy dinner. It's like Harry Potter style. And the guy opposite me - bearded white dude says so what do you do? What do you do? And you're supposed answer, right. So what do you do? And so I was a young chap at the time. And so I told him, I said I study the genetics of severe obesity. And I remember what he did to my dying day. He went, do you know what your problem is? Dude, I'm trying to have dinner. I don't know what's your problem? And then he went, you give fat people exactly like that an excuse.

Ahh.

That's Giles Yeo. Today, he's a world renowned geneticist at the University of Cambridge. He's a pioneer in the field of obesity research. But that dinner party he's describing was 20 years ago, at a time when researchers had very different views on what causes obesity.

At the time, I was just saying, look, do you say that we're giving people an excuse if they have muscular dystrophy? Would I suddenly be giving them an excuse? And he went, yeah, but you have no choice when you get cancer or you have no choice, when you have muscular dystrophy, you have a choice about what you eat. I don't think I convinced him. And so till that day, I didn't have to try and convince other people, I guess.

Professor Yeo says this conversation was the catalyst that kickstarted his career.

And it was from there. I then did it as more than a job. I started it as a job, like all of us sometimes do. You're just doing it. And I was doing my genetics thing. But it was that encounter with that guy I cannot remember his name now...

Dumbledore.

Yeah. Dumbledore. That's the reason why I stuck in the field.

Professor Yeo went on to conduct groundbreaking research that shows obesity is not always a choice. It's a disease. And not just any disease, but a brain disease. And what's more, for some people, the desire to eat more or eat less comes down to our genes.

I guess in casino terms, the house will always win if the die is weighted just a little bit one way versus the other.

It's a very new and provocative way of thinking about a condition that impacts more than 40% of Americans. But the thing is, this approach could have big consequences for the way that we treat obesity, the way that we prevent it. So today I'm chasing life. I sit down with Giles Yeo. I got to tell you, he does a really excellent job of explaining all this without shortcutting the science. It is still a controversial topic in the medical community and in general, but today I think we're in good hands. So I hope you're ready. I'm Dr. Sanjay Gupta, and this is Chasing Life.

'You know that story Professor Yeo shared at the beginning of the episode - that awkward dinner party and his senior colleague calling obesity a choice - that really sticks with you. It was obviously an instance of fat shaming, but I also know there are a lot of folks out there who might point out deciding what you eat and how much you eat is a choice. So I wanted to start there. I asked Professor Yeo for his response to that.

You're right. So your body weight is going to be a function of maybe hundreds, maybe thousands of feeding events over the past few years. But imagine if, because of your genetic hand of cards, just what you got from your mom and dad, you are a few percent less likely to say no. 5% over thousands of feeding events is hundreds of thousands of calories. And so, over the period of time, that food intake does begin to influence your body weight. It is not a choice.

That's fascinating. I think anybody who's listening to this can't help but think about their own personal situation. I'm pretty diligent about my eating. There are people within my family who have obesity. I get to the point of the day, sort of near the end of the day, where I start to have this food chatter. I'm starting to spend more time in the kitchen all of a sudden, you know, and then the pantry closet. And it is a battle of wills constantly. And I think to myself, okay, I have to win this battle of wills. But for some people, the odds, as you say, are really stacked against them at those points.

So I guess this does two things which speaks to it, right? This chatter occurs with me as well. You know, I do love food. And I think about it and I know what I'm going to have for dinner tomorrow night, probably even. And yes, I mean, we you and I probably have a little bit more. I don't want to use the word willpower. People says we have more willpower and I don't think that's the case. I think we have some internal signal, internal hormones or whatever you want to call it that's actually happening. That is putting a specific drive on how likely we are to say yes or no to food. And you can imagine, like as a thermostat for some people who are skinny and have a six pack. You know, I have a one pack. If you're skinny and a six pack, then fine. You might think you're morally superior, but actually you probably have less chatter, whereas there are going to be people with far more chatter than you and I that really the chatter starts early in the day. The chatter is louder. And so if you don't actually take care of the chatter, you can't do anything. You can't proceed in life. And it's a spectrum. It's not that there's some people who do and don't. There's a whole volume control of chatter. I mean, for lack of a better time, that some people don't hear it at all. And other people, it's a shouting, you know, shouting noise that they cannot do anything about unless they feed the chatter, unless they feed themselves.

You know, it struck me when I was reading through your work, you've been studying obesity since the 90s. How much have we learned, do you think, in terms of both scientifically and even culturally around obesity during that time? Over the last 30 years or so.

I think we've learned a lot. One of the important things we've learned is that obesity is a brain condition, for lack of a better term. Okay. See, when we first started studying it, the very, very first mutation that was identified was in a gene called leptin. And leptin is produced from fat. That seemed to make sense, right? Maybe obesity was a fat problem. Maybe obesity was a stomach problem. Maybe obesity was any number of different things. But with all the info that has come, it is now clear, crystal clear, unequivocal that it is a brain problem. It is a problem of our brain influencing the hunger. So hunger is a brain scenario, even though the feeling of hunger comes from your stomach. And we now know that obesity is just your brain influencing what you eat and how you eat. I guess that's probably the biggest thing. The other thing we've learned is that that different people, we can say different ethnicities. Do your genetics really, really do influence this. So you can do it from an individual basis like within one specific ethnicity, but you're always going to get fat and thin people. But if you take the 35,000 foot view and looked at at East Asian people, people that look like me, South Asian people, people that look like you, you know, and how we react to the environment, how more or less likely we're going to become ill, depending on how large we are. So it's the genetics and the fact that our brain has such a key role in obesity.

I know it's always hard to answer this question, but do you, do you how much do you weight genetics in a situation like this? And and again I'll preface by saying, so my dad is one of five brothers okay. And he immigrated obviously to the United States. His brothers are in various countries around the world. Two of the brothers have struggled significantly and have had obesity at various times. One has obesity now. How much of this do you think is genetics versus other?

'There is a number. Actually. As with most human traits and behaviors, a lot of our understanding of genes versus environment has come from the study of twins. And actually. If you study twins, then there is a range. But the heritability - so this is the percentage of a variation of a trait that's down to your genes versus the environment - the heritability of fat mass weight is between 40 and 70%. So if you take an average it's probably 50-50. There is a big range we can discuss why I guess, but 40 to 70%. So if you take an average then it's probably 50% your, nurture and 50% your nature, shall we say?

Gosh, you know, that's actually higher than I would have even thought. You know, I think a lot of times when we trying to look at this common refrain, look, so much of this is within your control and still a fair amount is within your control, you're saying. But you know, half of it being your genes. That's a significant number.

'I will never, ever be able to run as fast as Usain Bolt because of my genes. But it doesn't mean that if I train, I won't run faster than I do now. And so your genes will sort of put you within a range of possibilities, like, I'm never going to be as a twiglets, I'm never going to be a stick insect. Right? But it doesn't mean that if I look after my diet a bit better, you know what I mean? That I won't be able to be a little bit a little bit leaner. And so I guess that that is the challenge where people say you can do something about it - to a degree. Okay, that is more difficult than others, but you will never, ever be able to completely fit your genes.

If someone has normal physiology, you know you're checking their blood sugars and their insulin tolerance and blood pressure, all these kinds of things. And let's say those things are all normal or within normal ranges, yet they have a BMI that would qualify as having obesity. How do you sort of define those folks? They're physiologically healthy and yet they carry too much body weight.

'Yeah. So why is it bad to carry so much body weight? And let's be more precise with the language. Why is it bad to carry too much fat? It's rarely because of the actual obesity of itself that you get ill or die. In other words, I mean, there are gravitational issues, sleep apnea, arthritis, that kind of thing, and the inability to move as much. So it's the lot of inconvenience. I'm not belittling it, but actually what ends up killing you are the whole host of co-morbidities, type two diabetes, certain types of cancers, Alzheimer's, high blood pressure, etc. That's what kills you. Now, why that does is I think there's this concept called, lipo toxicity or being poisoned by fat. So people misunderstand what happens when you gain or lose weight. They think that you gain fat cells and lose fat cells. And that's not true. Your fat cells are like balloons. They get bigger when you gain weight and get smaller when you lose weight. And the safest place to store fat is in your fat cells because they are professional fat storing. Okay. But the problem is at some point your fat cells will become full and then your fat has got to go somewhere else. And when the fat goes into your muscles, your liver, your pancreas, your kidneys, into organs that are not designed to store huge amounts of fat, that is when you end up being ill. Okay, that's the key thing here. Everyone's fat cells can expand to differing amounts before they become full. When someone is larger, BMI, whatever, but actually all their metabolic parameters look fine, then I think the likelihood is they probably are fine. I mean, maybe they won't look good, you know, whatever good means, maybe they won't look good because they don't have a six pack, but they are healthy. You know, for all the metrics we're measuring now, because they are going to be skinny people who look perfectly happy but have type two diabetes. So this is why I think we need to consider not only the weight, but your metabolic health. And they're going to be a number of measures that we can use before we say that someone has obesity.

So does that throw into question then the idea of classifying obesity in and of itself as a disease. I mean, if someone has normal physiology yet they have high body weight, have too much fat to be more precise. Is it still a disease?

It is if you redefine the term obesity. I it is, it is. I maybe doing some verbal gymnastics here, but I think it's an important nuance. The moment we begin to understand that obesity is not high body weight, but obesity is a state where high body weight begins to influence your health. Then it is a disease. I'm not saying we're there yet in terms of of calling obesity obesity, but I think we should get there because then I think we are having a clearer conversation about what it means, who you medicate, who you medicalized when we're talking about high body.

Yeah. And I think you might be the perfect person to sort of redefine some of this stuff. I mean, you know, it's interesting that BMI, as you know, is is a pretty antiquated, blunt measure for individuals, just base your whether you have a disease or not, on some metric from a couple hundred years ago that was mostly European soldiers not taking into account children, not taking into account different cultures, I think is...

Or women!

Or women for that matter. Oh, I yeah, that would be an incredible thing for you to do. I mean, it'd have to be simple. Obviously you can't make it too complicated, but is there some... I'm not even asking a question here, but I just thinking out loud. There must be a better way to ultimately define this for people.

I mean, obviously, ultimately defining it would be. And this is difficult to do because it doesn't cost money, would be to have some kind of measure of metabolic health now. But leaving that aside, okay. Because then that means going to a medical professional. I think there are some easy wins, even if they're not perfect. For example, imperfectly work in your waist size. Hey, even there's no waist size or even better, your waist to hip ratio. So your circumference of your waist over the circumference of your hip. If you take that ratio, it gives you an idea of your body shape. Do you have a big bum? Do you have a big tummy? Do I look like a sausage? Right? It gives you an idea of what that thing is and what that's important because it tells you where your fat is being right and placed given a higher BMI. And famously, we know that pear shaped people, largely women, but not exclusively versus apple shaped people, largely men, but not exclusively. That men put fat in a different place and are more likely to have metabolic disease. So I think if you actually take BMI and then work in your waist to hip ratio, I think even there that will draw in the precision far, far, far better by bad people don't do it as much as they should.

I'll bet most people don't realize that your waist size and your waist to hip ratio can actually be more helpful than BMI alone. That's because a lot of the fat stored around our waist is something known as visceral fat, a potentially dangerous type of body fat that surrounds your liver and your organs. It can contribute to serious health issues. Heart disease, type two diabetes, strokes. So if you'd like to figure out your waist to hip measurement on your own, here's what you do: measure your waist around your belly button area. Then measure your hips at their widest point. Divide your waist size by your hip size and that's your waist to hip ratio. To give you some context, if you're a man, health risks seem to increase substantially when that number is 0.9 or above. For women, it's 0.85 or above. That's according to the World Health Organization. But the good news is you don't have to be defined by those numbers. And Professor Yeo says it is possible for us to treat and prevent obesity, but it's going to require a total rethinking of our approach.

People worship the calorie, people count the calorie. And then by doing that, you don't focus on actually improving the quality of your diet.

That's an issue. Now we're going to talk about it after the break.

'So I gotta a start by telling you the way Giles Yeo thinks about obesity, it's pretty new for me -probably pretty new for you as well. He calls it a disease, but he also takes it a step further. He classifies obesity as a chronic and relapsing brain condition. Think about that. That's a huge shift in the way we've thought about obesity in the past. Before, it was often viewed just as laziness or a failure of willpower. So what does that mean in terms of how we treat obesity as well? Professor Yeo thinks there are some big changes coming in that new drugs like what Wegovy and Zepbound could help because they actually target the food chatter in the brain.

'These new class of drugs that now work Ozempic, Wegovy are all modified gut hormones. And these gut hormones, which are released every mouthful of food we eat, it goes down through the your tube and out the other side releases hormones and most of these hormones make you feel full. And if you modify one of them - GLP one - so that they stick around the blood for longer. They end up signaling to the brain, but they know where they're supposed to go to the brain, because the gut hormones are there to signal to the brain to tell you, stop eating, you are full. And so if you're able then to target the brain in sort of like a homing missiles, sort of a scenario, a self guided missile, then it works better. And that's how these drugs work. First of all, we understand that the brain needed to be targeted. We needed to find a safe way to target the brain. And what these new class of drugs do is they safely target the brain to get you to eat less. So I think that lesson has been learned.

They're expensive. Professor, you know, I mean, you're talking $1,000 plus a month, potentially. I'm a doctor. I like to obviously do everything I can to help my patients. But it seems a little bit ridiculous, to be honest, in terms of what the cost is of these drugs and what we're asking people to do. Are we missing the boat here in some way, or what is your overall impression?

You're right. I think that it is a lot of money on the face of it. But if you manage to reduce the burden of cancer, of heart disease, of high blood pressure, of hyperlipidemia and of everything else that's there, and heart disease is still the biggest killer in the world right now. Strokes everything. Then the amount of money you'll save is going to so far outweigh the amount of money we actually end up spending on these drugs. And on top of that, there are a lot of money now, but that's because there is a fund. The thundering hooves of this class of drugs that are coming up and this very soon, that's going to be a huge open market warfare on these drugs. And that will drive down the cost. It's not going to be look, it's not going to be pennies, but to my mind it will fix itself. But definitely the costs of not treating far outweigh the costs of treatment.

Let me flip that question then and ask you this. My BMI is not is not high. But I have a terrible family history of heart disease. And this is the sort of thing that it's not that uncommon among South Asians in particular. But, you know, my grandfather died of a heart attack at age 50. My father had bypass surgery when he was 47. I'm going to be 55 now, you know. So I got to tell you, you know, I try and do everything, professor. I exercise every day. I am very diligent about my health. I do cardiovascular training, but I still worry about it all the time. And then these drugs come out and they say, hey, look, people's lipids came down, their blood pressure improved, their food chatter went down. And I'm thinking, I don't qualify for these drugs. I'm not saying I should take it, but have I wondered about it? Absolutely.

'And I think that the more we learn about though, it may very well be the case one day. Not at the moment. I just want to be crystal clear. Not now. Not at the moment. Not now because I think we need to know all the science. But let's say everything is safe. Imagine. Let's imagine a world a decade, 22 decades from now, where we know all the long term causes. We know the dosing regime. I mean, at the moment when we walk into a drugstore, okay, and we buy Tylenol and we actually we take it, oh, I've got a fever. Oh, I've got a back pain. And they take it. Are they side effects? Yes. If you have a whole bottle of Tylenol you can still end up in hospital. But we give it to our children, right? We go and we understand the dosing regime. We understand and we now self-medicate ourselves with Tylenol. Now, I'm not saying that this will become Tylenol, but if it's going to be safe and if you're going to be in the situation where actually we understand a lot more about this and it becomes a pill, okay, why would you not take it, if you will, the way we take Tylenol now, why would you not do it?

I'm curious, what do you make of the rising rates of obesity overall? I mean, more than half the world is expected to be overweight or obese. You know, in the next ten years or so in the United States, were probably three quarters of the population either already overweight or have obesity. It's a broad question, but if you were somebody who was in charge from a policy perspective, and maybe you'll be asked to do something like that, what sort of guidance would you give at a policy level?

I mean, you are completely right. I think over the past, I think ten, 15 years, we have reached an inflection point in, in human evolution where there are now more people on this earth dying because of over nutrition as opposed to under nutrition, whereas before we never had enough food. We now have too much. And in fact, if you actually go to the and this is a key thing, the 2019 Unicef Childhood Malnutrition report came out and there was a line in there which I think crystallizes the problem that we actually have. And it said, why are so many children getting not enough of what they need? And we understand what that means. And so many more children are getting too much of what they don't need. So how do we tackle it? I think part of the problem, there's a huge socioeconomic gradient to the risk of obesity that you're more than twice as likely to end up with obesity if you are poor, than if you are not even rich like middle class. And a large part of it is down to the food system in which that we, at least in the United States, in the UK, where where I'm from in Europe, that actually unfortunately, the healthiest foods at the moment are not the cheapest foods. And so the poorer you are, the more likely you are to have food that is not great for you. So if I were made president, Prime Minister, whatever your leader is called for a day, I think what I would do is make healthier food cheaper. In fact, not only make it cheaper, I would make it the cheaper and more convenient option so that if you are Mrs. Smith with three minimum wage jobs, having to feed your kids, and you walk into the grocery store and you only have ten bucks, that that ten bucks buys you healthy food. Now you and I can go get not healthy food. That's not an option. That's our privilege. That's our choice. That's our stupidity. Whatever words you want to use. But we have to make sure that we tackle this on an equitable basis, which means making healthier food cheaper and more convenient.

I love it. I mean, I remember reading a study once where it was cheaper to buy a caramelized apple rather than just a a healthy...

Apple apple!

Clean Apple, yeah, it was kind of amazing. You've been pretty vocal about calories. I've watched again some of your lectures, read some of your papers, and I know the answer to this because I've read your work. But do you count calories? Should people count calories?

I don't think calories are useful. Let me tell you why, since whenever I say this people think I'm anti physics, I'm not anti physics. I understand that 200 calories of potato chips is twice 100 calories of potato chips I think, but so is 200g of potato chips, 100g of potato chips, and no one is trying to compare 200g of potato chips to 200g of carrots. So I think the problem with the calorie is while on an individual food, it gives you how much food you're eating. And that's yes, clearly a lot of us need to eat less food. It does nothing to tell us about the nutritional content of the food. So calories as a measure are nutrient blind. So you could be eating just potato chips or French fries the entire time. Oreo cookies. And that's fine in small amounts, but not healthy. It doesn't tell you about protein, fiber, micronutrients, nothing. That's why I have a problem with calories. People worship the calorie, people count the calories. And then by doing that, you don't focus on actually improving the quality of your diet. And that is an issue, I think.

So how do you approach this in your own life then? How with that in mind, in your own research in mind, how has that impacted your own eating habits?

'Well do as I say and not as I do. I think it's the it's the first thing of all. So I think I think, you know, I could I you lose about 10 pounds. Yes, I could. In fact, my wife tells me I need to lose 10 pounds, but we'll leave that alone. I am privileged and I have a choice, but I tend to do most of my own cooking. I probably have one night a week, Friday, that we go out and get takeout. Okay, because that's the night I don't cook. If you can do it, then actually a good start is actually cooking because then you know what you're putting in. Yes, sometimes you added a bit more butter or you add a bit more of this, but the reality is you're never going to put as much fat, sugar and salt as you would if you get it pre-processed or what have you. That's just the way it is. I don't judge people for what they eat. I think we can all eat things in differing amounts. I just think we need to think about the quality of the food that we're eating. But I speak from a very privileged position. I understand that, and I still think that we need to work with the food system that we currently have, and we need to work with the food manufacturers that are currently there, and demonizing them is not going to help because they produce our food, and we need to try and export to them to produce healthier food. And don't tell me to replace a chocolate bar with a banana, because sometimes life demands a chocolate bar and sometimes life demands a banana. The question is, can we make a healthier chocolate bar? And so I do think that's important because sometimes you want to talk about sometimes you want a cake, sometimes you want frozen lasagna, sometimes you'll eat a carrot. Can we make sure that everyone gets a slightly healthier chocolate bar when they need a chocolate bar? And I that's what I'm.... people think now that I work for the food industry, I don't. I work for the University of Cambridge. But I think we got to be pragmatic.

You are a foodie. I follow you on Twitter and you're a foodie. Everyone should follow you on Twitter. They should read your books. I mean, who better to learn from than someone like you and I? And I can tell that you're you're an optimistic person. Are you optimistic when it comes to the issue that we're discussing? I mean, if we're to have this conversation in 10 or 15 years, how do you think we'll be talking about obesity?

I am an optimist. I do see a change in the needle in the way that people talk about obesity by the fact, look, we're having this conversation. So I do think that there is at least a needle that is moving. The biggest challenge is to convince the policymakers that it is a problem and that we need to do more than rely on the drugs. I sense that there are going to be a lot of politicians who think that the drugs are an easy way out, not for the person, but for the government. They'll say oh, this means we that we don't have to build more playgrounds for, for for the kids. We don't have to make sure that the, that the cycle lanes are a bit better to go to go into the school. So I think that I am optimistic for the treatment. I'm optimistic for the societal discussion of it. I'm less optimistic for now about the policymakers, sadly.

With all you know, when you're walking down the street and you see someone who appears obese, what goes through your mind immediately, just reflexively.

It's changed over the past decade. The thing about obesity is that it is a very public. If you have heart disease, I don't know if you've had disease or diabetes, but I know when you have obesity. On top of that, I know what you eat when you're in a restaurant, and I know what you shop when you're in the grocery store. It's a very public thing. And so therefore everyone judges, including myself. Now, now I shut out. First of all, I don't print. I don't say it's in my head. And so I tackle the demon in my head and I says, listen, mate, write about something like that. But a lot of people who don't have the the advantage of the knowledge that I have because I spent so long in the field will make a judgment. I'm not saying I don't blame them. I say we need to educate them about that, but it's just so public. It's just so there we it's just very different to other let's called use the word diseases, other diseases out there, which tend to be silent. You don't tend to actually see them there within yourself rather than something so external and so public.

What a pleasure. And it is Friday. We're recording this podcast on Friday. So does that mean it's takeout night tonight for you?

It's... Normally it is. I'm on a plane in New Zealand in two hours. So, so, but but I'll eat on the plane.

Well, thank you for spending this time with us. I learned a lot. I really been looking forward to it. So thank you so much, sir.

Thank you so much for having me on.

That was my conversation with University of Cambridge professor Giles Yeo, a world renowned geneticist and pioneer in the field of obesity research. Got to tell you, I got a lot out of this one, and I hope you did as well. Coming up next week on the podcast, we have another very special guest. Author and comedian Lindy West joins me on Chasing Life.

Having had my weight fluctuate, I know for a fact that the smaller you are, the nicer people are to you. And it's just like heartbreaking to know that.

'One more thing before we go. I know we've been talking a lot about weight this season, but let's not forget how food also brings us joy. What is your favorite comfort food and why? Give us a call (470) 396-0832. Leave a message or you can record a voice memo and email it to ask sanjay@cnn.com. We might even use it in a future episode. Chasing Life is a production of CNN Audio. Our podcast is produced by Ery Mathewson, Jennifer La, and Grace Walker. Our senior producer and showrunner is Felicia Patinkin. Andrea Kane is our medical writer and Tommy Bazarian is our engineer. Dan Dzula is our technical director. And the executive producer of CNN Audio is Steve Licktieg, with support from Jamust Andrest, John Dionora, Haley Thomas, Alex Maniserri, Robert Mathers, Leni Steinert, Nicole Pesaru, and Lisa Namerow. Special thanks to Ben Tinker, Amanda Sealy, and Nadia Kounang of CNN Health and Katie Hinman.