World's No. 1 Exercise Professor: "Our Comfortable Lives Are Causing Cancer", "The Truth About Running", "Hand Sanitiser Is Making You Sick!

Cancer, violence, aggression, obesity, stress. If you want to fix all your complex problems, well, this is controversial, but the vast majority of the evidence suggests that... Daniel Lieberman, a Harvard professor who uses the information of our evolutionary past to understand the health crisis we are in today, and educate people on how to live a long, healthy life. The vast majority of us in the Western world will die from a mismatch disease. For chronic stress, that's what we call a mismatch. Obesity, heart disease. Many cancers are mismatches, and it's because we now live in a world where we're

able to have incredible levels of comfort. With all this choice, for example, the number one medical complaint is back pain. Because I'm sitting in this comfortable chair, I don't have to use any of the back muscles. So we develop weak backs that don't have any endurance. We know that people who sit a lot at work, but then also sit a lot in their leisure time, and then weigh more risk of disease. And if you aren't physically active, you don't grow as much skeleton, and then when you hit 25 to 30. For the rest of your life, you're going to start losing bone. Oh, shh, I got it. Even in this highly sanitized world, where much more life

is likely to develop allergies and various kinds of autoimmune diseases. Because our immune systems are so unchallenged, they've ended up accidentally attacking us. Also, famous studies show that the richer the country, the higher the rate of cancer. The angladeshi women who moved to England, their cancer rates go way up. Because of diet and physical activity and stress, things that have changed in our modern world for which we are very, very poorly adapted. There's a lot to take in. Is there an actionable conclusion that I can do today? That is going to reduce my chances of getting one of these mismatch diseases. Yes, I think there's two. The first is...

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Daniel, what is your job title? I'm a professor of human evolutionary biology at Harvard University. And what does that mean? It means I get to have a lot of fun. I study... Well, my department studies how and why humans are the way we are. And we're also interested in how and why that's relevant to humans today.

My particular specialty is I study the human body. I'm interested in how and why the human body is the way it is and how that's relevant to health and disease. And I'm most interested. Most of my work is on the evolution of human physical activity, but I'm also interested in diet and other ways in which we use our bodies.

What is it, Mata? Well, because we weren't designed. We weren't engineered. We evolved. So if you understand why we are the way we are, you have to understand that evolutionary history. And if you want to solve problems, if you want to deal with big issues that we face today, obesity, heart disease, cancer, violence, aggression, all of these things have an evolutionary origin. And an evolutionary origin is crucial to helping us come up with solutions.

Does what we eat play a role in the sort of starting point of our stories and how we began to eat and thinking about farming, hunter gathering and all those things? Because when I look at human beings versus a lot of animals and you talk about this in the book, we are remarkably fragile and inadequate in comparison. Like our eyesight isn't that great. We're like super weak. I think you say that like most monkeys are stronger than we are. Squirrels can run faster than us.

Well, I think we actually exaggerate our fragilness and weakness to some extent. So chimpanzees, our closest relatives, are about probably about 30% stronger than we are. You would not want to arm wrestle a chimpanzee. And most quadrupeds can run way faster than we can. We have this sort of story about human evolution that it's been a sort of triumph of brains over brawn.

We have tools and language. And that has enabled us to conquer the world and become the dominant species. And there's some truth to that, of course. Technology, language, communication, cooperation, all our essential parts of the human success story. But I think as athletes, we're pretty impressive. We can outrun most animals over long distances. So we're really impressive in terms of endurance, both men and women. We can throw, we can kick, we can do all kinds of things that my dog can't do.

As far as diet is concerned, you know, we're the ultimate omnivores. We can eat anything. I mean, most animals have very kind of constrained diets. There are certain things they can eat. Most of the things out there they cannot eat. We've managed to figure out because of technology, cooking, food processing, but also because of the nature of our digestive system, we can eat just about anything on the planet.

People can be vegans. They can be, you know, they can eat all meat diets. They can, you know, it's astonishing how much variety humans can get by with. You know, our, you know, our liverers can turn anything and anything you can, you can, we can turn fat into carbohydrates, carbohydrates into fat. We have an incredibly astonishing range of foods that we can consume.

When we're thinking about our sort of evolutionary history and the hunter gatherer tribes that still exist in the world, I think I fall in into the trap of believing that all the answers we're looking for about how to be healthy humans in the modern world can be found just by looking back at our hunter gatherer ancestors. Is that true that they hold the answers to how to live a happy, healthy life?

Well, it's like everything is complicated, right? I mean, to some extent we call that paleo fantasy. This idea that if you just go back to being a hunter gatherer that you'll have no problems, right? And that hunter gatherers have no violence and they don't get sick and, you know, all as well. Well, it's not so simple, right? I'll give you one example, murder. We have this idea that humans have become incredibly violent since the origins of farming, right?

But if you actually look at the ethnographic record, hunter gatherers are just as violent as the rest of us. They're human beings. They kill for passion, they kill for greed, they kill for, you know, for, you know, there's a murder. There's warfare among hunter gatherers even in some parts of the world. Yes, it's true that hunter gatherers don't have the same problems with obesity. They don't have metabolic syndrome. They don't have, they probably don't get heart disease.

It leads to the extent that we do. There are plenty of things that they do that are worth emulating. But, but they're not role models in every respect. And, you know, what natural selection cares about is how many offspring we have who survive, right? That's the only thing natural selecting cares out. It's the equation of life is food in babies out, right? That's what that's what we're here for, right? As far as natural selection is concerned.

No happiness. We're not here to be happy. We're not here to be nice. We're not here to be fulfilled or anything like that. Although it's good when that happens, right? We evolved to be hunter gatherers. Our ancestors were hunter gatherers for millions of years. But those, but the adaptations they have are primarily and first and foremost about reproductive success.

So, we didn't evolve to eat foods to make us healthy. We evolved foods that would increase our reproductive success. And we evolved to be healthy only to the extent that health promotes reproductive success. So, you can't just assume that because our ancestors did something, it must, it's, it's optimal for health. It's, you can, it's more reasonable to assume that that's optimal for reproductive success. And remember, it's in those environments and in those contexts and things have changed.

Talking there about what they, one of the big debates I've, I guess that's an ongoing debate is whether we are evolved to eat meat or were meant to be interesting use of words, vegans or vegetarians. What's your perspective on that? Because I've sat here with people who are really, really passionate about the fact that we're not supposed to evolutionarily, see how could I try to say that word because I don't know how to say it, meant to eat meat.

Well, that's just nonsense. I mean, humans have been, humans started eating meat about two and a half million years ago. There's no question, at least two and a half million years ago, maybe more. And there was no question. It played an extremely important role in our evolutionary history. Even chimpanzees are closest cousins eat meat occasionally when they can. They don't get it very often. Maybe about less than five percent of their diet is meat.

From an evolutionary perspective, we evolved to have meat as part of our diet. But of course, you can be a human being and not eat meat and do just fine. In fact, there are some advantages. Because remember, we didn't evolve to be healthy. So just because our ancestors ate meat or didn't eat meat doesn't mean that's optimal for health today.

That's a very impoverished way of thinking. It's just illogical. Our ancestors didn't evolve to read. So should we not read? Reading is only a few thousand years old. So that's just not the right way to think about how to use evolutionary theory and data. The fact of the matter is that we evolved to eat just about everything. We are the ultimate omnivores. It's astonishing the range of foods that we've hunter-gathered as eat, typical hunter-gatherer, for example, there's data from Kalahari.

I think they eat about 800 different kinds of plants, many different kinds of animals. And that's just the Kalahari. Humans moved over the last few hundred thousand years to pretty much every corner of the planet. And in every part of the world, they found foods to eat. They humans lived in the Arctic, where there's almost nothing but meat in many seasons. You know where you get plant food in the Arctic in the winter? By eating the contents of the intestines of the animals that they hunt.

People lived by oceans and fish and die for shellfish. They live in rain forests and eat bugs and birds and monkeys. Everywhere you go on the planet, people figured out to eat various kinds of foods. And one of the ways we became omnivores is that in addition to having incredibly flexible digestive system,

we also have technology to process our food. So by cooking our food, by fermenting our food, by grinding cooking, cutting it up, we've been able to essentially adapt ourselves to an astonishing range of environments, hence an astonishing range of foods. And so now tell me, like what diet are we able to eat? It's an impossible question to answer. Is there a point in our history where we learned how to hunt and gather? And was that the point where we started really eating more meats?

Yes. So, well first of all, it probably wasn't like a, you know, a day, you know, lightning bolt came down from the sky and all of a sudden, bam, you know, so we figured out a hunt. After all, our apocasins will hunt when they can. But as soon as we became bipeds, which was probably around 7 million years ago, walk on two feet, right?

We became slow, right? You know, chimpanzees when they run can gallop essentially on four legs, right? And they can be really fast. They can't run long distances, but boy are they amazingly fast. And they can climb up trees like no human can. Around 7 million years ago, when we split from the chimpanzee lineage, it looks like we became, you know, a obligatory two-legged bipedal creatures.

And as when you have only two legs, you can only run half as fast as when you can have four legs. It's like having a cylinder car with half the number of cylinders, right? You know, you can just produce less power, right?

And so our early ancestors must have been slow. There's no way they could have run that fast and certainly not fast enough to be great hunters. So I suspect that compared to chimpanzees, they were probably poor hunters because they couldn't run down creatures the way chimpanzees could, right?

So probably for a few million years, meat was probably rare in the diet. But then we begin to see starting around, you know, around three million years ago, maybe a little bit older stone tools in the archaeological record. We find bones with some cut marks on them. And starting around, you know, 2.5, 2.6 million years ago, we have archaeological sites with bones of animals with cut marks on them, stone tools.

And those animals were clearly butchered. And by two million years ago, we have clear evidence that humans were actually hunting. You know, we have clear evidence that these animals weren't just scavenged. They were definitely hunted.

So that means that sometime between around three and two million years ago, hunting became part of our ancestors repertoire. They're also making tools. They must have been cooperating. They probably had some form of communication or whatever. We don't know exactly what it's like. And they're probably eating a wide range of foods, including what we call extractive foraging. So they're eating tubers underground storage organs, right?

So instead of just plucking berries off plants, you know, they're actually finding high quality foods that you have to dig for, right, under the ground. Like just think about a potato. It stores its energy underground. So these are rich sources of food, but you have to be able to dig for them and find them, right?

So this combination of extractive foraging, so not just not just plucking leaves or berries off plants, but finding high quality resources, hunting, cooperation, toolmaking and tool using altogether. That's the hunter gather away of life, right? And that emerged sometime again between three and two million years ago, and that was transformative. That's the, that's really, I think, one of the most important shifts that occurred in human evolution.

And that's also incidentally when we see this shift in our bodies, right? When we, when we going from being more essentially more ape-like, like Australia pests, which had short legs and long arms and they have small brains and, you know, they're, they're not apes, but they're, but they're more ape-like.

Two basically bodies that are more or less like yours and mine. So we have a fossil called the dracana boy. His real name is Nariakutamase from the west side of Lake dracana, Northern Kenya. He's a homorectus who was probably about eight years old when he died.

And, you know, from the neck down, he's basically like you and me. His, his, his head is not quite like ours, but he's, he's a big brain, not as big as ours. He has a, doesn't have a snout like a, like an astralopathy. He's got a vertical face.

He's got teeth that are basically like yours and mine. He's basically very, you know, on that path towards being a human. And so hunting and gathering and the genus homo kind of come together. And that was, I think, one of the most important major shifts that occurred in our evolution. Maybe the most important actually, more important than even the evolution of our own species.

And that allowed us to become good hunter gatherers. So we have this nose that sticks out of our face, whereas like a lot of our cousins look more like Voldemort, like they kind of have the Inver. And that's a sign of when we became hunter gatherers, right? Yeah. So that external nose, right? So chimpanzees are flat nose like a dog, right? And that external knows that you and I have, which is of course fantastic for holding our classes, right? Well, you don't have classes. Not yet, at least.

Is is a, we think it's a kind of a humidifier. So when air goes into our nose, it has to go through a little nostril. So it's a little what's called a Venturi throat. So it goes through a very narrow. And then into a larger space that has to turn a right angle to get into the inside of our nose and then has to turn another angle to get down into our that pipe we call that the pharynx that brings air to the down to our lungs.

And all those twists and turns and changes in diameter cause the air to be more turbulent. So the air instead of flowing in a kind of a straight, right? Because it has these four fortices. It's it's got all kinds of currents. And when that happens, that means that the air has more contact with the the the mucus membranes in our in our nasal cavity.

So it can pick up moisture on the way in pick up heat on the way in. So our lungs are don't get dried out. And on the way out, it can recapture that moisture so that we don't we don't lose that moisture when we're walking or for that matter running. So if you and I'm really cold day, you can do a simple experiment right when it's below freezing. If you breathe out right you see all that steam coming out.

Do the same thing breathe out through your nose. You'll see a lot less steam and that's evidence of this this ability of our of our noses to trap air. And that's because of the six-terral notes. So so that happens around two million years ago or so. We can see that because on the in the fossils, we can see that the margin of the nose and you can see that it's lipped out. It's what we call averted right.

It sticks out and that's evidence that we had these cartilages that sticked out suck out and gave us our modern nose. So so if you if you went two million years ago and you met in your your ancient ancestors, they would have had a nice schnauz. Does what does this say about how we breathe today because of there's been a huge conversation I think over the last couple of years about breathing and brec breath exercises and mouth breathing in particular.

I've had people on this show like James Nester who talks about how there's a lot of disease happening because we've kind of by habit become mouth breathes when we run.

But also so many people seem to be having a lot of problems with their sleep my girlfriend, for example, she uses nasal strips when she sleeps to try and open up her airways and I actually think she's going to have to have an operation but we've even got people in our team that seems like everyone's nose is what do they call it when it's bent the

deviated septum deviated septum, so everyone's struggling with this at the moment. Yeah, I have to say I'm a little skeptical of some of these arguments the idea that you can fix all your health problems by just breathing through your nose. Look, breathing is obviously very important but but the idea that for example when you run you should only breathe out through your nose. That's just that's just silly.

That's just not true. We evolved to breathe out of our mouth when we run where the only species that does that actually because it's an efficient way to dump heat when you're running you're generating huge amounts of heat. You have to dump it or you're going to overheat and you you breathe out through your mouth for that reason right to kind of to get the heat out of there right.

Breathing through your nose would be maladaptive and no elite runner on the planet breathes out through their nose when they're when they're running. I'm not sure where that came from and I just like to see more data to support some of these arguments about nasal breathing. I'd like to see data to support the effectiveness of those of those nasal strips. Sure breathing is important to their better and worse ways to breathe.

You know we're always looking for simple solutions right to complex problems and the idea that somehow fixing your breathing is going to prevent you from having a wide range of diseases is not true. And people have sleep apnea which is a serious issue. That's usually caused by well it's caused by a variety of things of course a deviated septum might be one of them obesity can cause it there's a number of other problems and of course once that occurs.

You know again you want to treat the cars not the symptom right so the best way to treat the cars of the apnea is not to put a piece of tape on your nose it's to it's to find the underlying cause by why that's happening in the first place and solve that deal with that.

And sweating sort of correlated to that turn in the fork in the road and I sort of hunt together a history because monkeys and even my dog Pablo he doesn't seem to sweat from anywhere other than his mouth I guess it seems like he's his panting is his way.

Exactly exactly so the way in which most animals cool down is by panting right they they breathe through their mouth or their nose right and there's there's air passes over these mucus membranes on the on the nose in the mouth and and and what happens is that the air by passing that air over the tongue or whatever causes you get evapotranspiration so evaporation so the air that the moisture.

And that goes from a liquid to a gas phase right and that of course costs energy so because energy is because of conservation of energy that means that for every I think milliliter of oxygen of water that goes that goes from water water to gas I think it's five hundred and sixty one calories calories calories at the small sea.

And that so that causes the tongue or the surface of the nose to cool and then there's blood right behind that blood blood in the tongue thing if you cut your tongue it's really bloody right. If you cut your nose right it's a lot of blood there's a huge amount of vascular chair in there all these arteries and veins right so that you cool down the blood that's just below the surface of the tongue and in the nose and then that cools down your body right.

So panting is how animals cool or you can even watch a lizard a lizard also does it's called color pumping it'll it'll actually you know that's how it cools itself down watch a lizard will run and it'll it'll basically pant and then it'll run again and it'll pant and it'll run again because it's prevent itself from overheating right now what we did is we've we have sweat glands so most animals have there's two kinds of glands right there's one's called apricot glands those are the grants we have in our you know armpits and around our genitals it's not.

They're genitals etc or in our ears they produce waxy sort of fatty substances right there's the ones that smell or ear wax that protects our ear so all most mammals have those apricot glands. Echron glands are watery glands and most mammals have them just on their palms their paws and their feet right so that they can just think about when you what your finger you can turn a piece of page right it gives you it gives you more grip on something so when you're trying to escape from a predator

sweating on your hands will help you run up that tree if you're a mouse or something like that a rodent so most mammals have echron glands just on their palms but in monkeys they started to evolve having some sweat glands on their bodies but not many and so chimpanzees monkeys have some

echron glands on their bodies but what we've done is we've increased that by an order of magnitude we have like ten times the number of ten times the density of echron glands that monkeys and chimpanzees and we lost our fur so and of course fur prevents air from

from convection of air next to the skin so when you sweat on your skin and you don't have fur you can have evaporation of moisture and then air takes that away quickly so you can keep evaporating moisture and then you can cool your body so we've effectively turned our entire bodies into a tongue

essentially and so we can dump amazing amounts of heat when we're physically active in hot environments and that was obviously important for ancestors when they're hunting right we have a huge advantage in the heat of the day because we can not only were good at running for all for you know because our legs and our muscles and our killies tendin and all these adaptations we have for running but we also have this incredible

thermoregulatory ability to dump heat which the animal we're chasing does not have and we can we can we can we can the little die of heat stroke but we don't know when that happened and it's possible that that our

that our strail of the ancestors before before hunting started because remember there are two legged creatures right and they're not they're not very fast so maybe in the middle of the day when when it was really you know hot that was the best time for them to go out and get food because that's the time of day when carnivores that

love to chase them right if I'm a carnivore and I want to might going to eat a gazelle or an astralipeth right astralipeth is going to be half the speed of the gazelle that's easy picking right so I'm going to go for an astralipeth so maybe our early ancestors forage in the middle of the day when it was really hot so that because they because they were too slow to run away from carnivores and maybe that was an adaptation

and so the ability to to dump heat effectively might have been really important for them so it's possible we just don't know that sweating actually came before hunting it's just simply at this point we don't because skin doesn't preserve in the fossil record we just don't yet know when that happened

what about a big brain did that come before hunting or is that a product of the fact that we started hunting it looks like more the ladder right so chimpanzees have brains you know typical chimpanzee might have about a 400 cubic centimeter brain like 400 grams think about it in grams right

typical human has a brain that's like 1400 grams so you know really like three to four times the size of a chimpanzee's brain for about five million years in our evolutionary history so the earliest hominins hominins as a term for creature more closely related to us the chimpanzee so the earliest hominins plus you know these astrayal epiths like Lucy they had brains that got up into the 500 gram range rarely maybe sometimes 600 but not that much

starting around two two million years ago brain size just starts to shoot up if you look on a graph right and that's of course around the time we started hunting but it's really the time we have hunting and gathering and so I think it's the whole system it's it's not just meat although meat must have been important component of it but the whole hunting and gathering system is really a way to get more energy right because you're you're processing your foods you're getting more energy

because you're cooking your food or you're processing it in various ways you're you're cooperating you're you're you're you're you're getting new sources of food such as meat and marrow and brains and whatever all of that together means that more energies available and when more energies available then there's less of a constraint on brain size because brains are expensive just right now

you and I were sitting right we're not really doing much of anything other than talking but one out of every five of our breaths is to pay for our brain our brain is using 20% of our metabolism right and so to have a really big brain means you have to have a lot of energy available to you and it's so most animals can afford big brains because they don't have enough energy

right with hunting and gathering you get more energy more energy means selection can now you know this the the constraints on having a big brain are now will release now you can get selection for a larger brain so individuals with bigger brains might have had some advantage over individuals with smaller brains maybe they were better at doing this that or the other and so you get selection for larger and larger brain sizes

and it really accelerates up until you know well it continues up until a few hundred thousand years ago when essentially brains reached basically modern size and then you get fat because you have so much energy and so it's all about energy but that kind of makes sense doesn't it you store more energy and then we started to get fat

well fat is really important for a number of reasons one of them is having a big brain so you know a human infant when it's born its brain is consuming half its metabolic energy like when when a kid is born 50% of the of the energy it's spending is just to pay for its brain

it's a brain on a little body basically right and and of course you can't stop feeding a brain brains require energy constantly right brains don't store energy they need a constant supply of glucose or or ketone bodies which you can use is when you don't have sugar available to

you can get those from fats right so infants human infants are born unusually fat a guy named Chris Kuzawa showed that you know we know that a human baby when it's born is about 15% body fat way more than any other species right and that brain that all that fat is really kind of an like money in the bank to make sure that that brain always has energy available to it and furthermore you had published a really cool paper a few years ago which showed that when an infants brain is growing

right the first few years of life when it's growing really fast that's when it's body fat levels are going down and when it's storing a lot of fat that's when it's brain isn't going very much so there's a trade off in energy between fat and brains as we're growing

so so big brains and fat bodies are intimately connected so we want to make sure our babies are fat a fat baby is an essential fundamental human adaptation and and the body fat that we have I mean the typical human is much more body fat than then then then most animals most primates have about four or five percent body fat most mammals have about four or five percent body fat whereas a skinny human has maybe 10 to 25 percent body fat right so that body fat is not only important for brains

but it's also important for our reproduction because a typical mother nursing for example right hunter-gatherers will nurse for about three years nursing is really expensive it costs about 600 calories a day to produce breast milk imagine you're a hunter-gatherer and there's not a lot of food around right you're in what we call negative energy belts you're not getting as much food in as you're spending right you can't just stop nursing

your infant is still working to require that energy so you draw down on your fat reserves right so having all that fat which goes up and down and up and down from season to season you store more fat in the good seasons you use that up in the bad seasons those are fundamental adaptations to keep us physically active to enable us to reproduce the way we do to pay for our babies we produce the way we do to pay for our big brains they're part of you know that you know

our kind of relatively high level of fat and our predisposition to store fat is fundamental to our species we wouldn't be here if we didn't have all that fat and I guess this is why the lighting is so hot right because well we never evolved to diet we evolved to put that fat on

to use it when we needed it right but we never evolved to get rid of that it was just never you know in an absence of obesity there wouldn't be selection for that kind of physiological system to lose fat without needing it because when we try and diet it does feel like our bodies are somewhat against us

when I hear about sugar cravings and you know many people have told me that if you do reason my diets don't work is because your body is trying to basically defend the weight that you're at because that used to mean your survival that's right we call that a starvation response right so when you go into negative energy balance which is what a diet is right you're spending more energy than you're using then you're taking in

your body goes into a starvation response your cortisol levels go up for example right it's a it's an emergency right it's like it's a cortisol is our stress hormone stress doesn't cause cortisol to go up cortisol goes up when we are stressed and it makes energy available to us and one of the things that cortisol does is it makes us hungry right when you're really stressed at night right studying for an exam when my students right they get you know hunger you know they get sugar cravings

right because they're cortisol levels because they're stressed because I'm going to give an exam in the next day goes up and then they want energy right cortisol also makes you store fat in visceral deposits so so so belly fat which is which is you know concerning right it's a it's a useful kind of fat right because the fat that we store in

and around our abdomen is is very hormone sensitive it's it's got lots of blood vessels so that fat is a great energy supply when you're you know you're physically active right when I went running around central park this morning when I was burning some of my belly fat but when cortisol levels go up that's like it also directs us to

bot deposit fat in those stores right and the problem with those stores is that they're also very inflammatory so when those fat cells get too large and they swell they become dysfunctional and they cause inflammation they cause chronic systemic inflammation which is just ruinous for our health it causes diabetes and Alzheimer's and you know heart disease all kinds of

diseases that that pretty much every major disease that we're worried about the mismatched diseases that we often talk about are you know many of them are our inflammation related and and and and that's why we're concerned about excess at a positive excess fat because excess fat causes inflammation.

So that means that people that are more stressed and more likely to have belly fat correct yes that's true so that's one of the reasons why stress is you know a risk factor for so many diseases psychosocial stress is a is a has a prenicious effects and that's why you know racism discrimination all those all those factors that can elevate stress commuting

have negative health consequences because it causes us to our cortisol levels to go up it causes our us to us to put fat in the wrong places it has a cortisol also turns your immune system down cortisol has all kinds of you know negative effects when it's when it's long-term and persistently high.

It's often been said that if you lose too much weight for example if a woman loses too much weight then her menstrual cycle will stop and I was thinking about this from an evolutionary perspective and you say how you know fat is essentially evidence of our survival so in some ways is that all if that is true then is that our body basically stopping our menstrual cycle to conserve energy basically you could think about it like our body saying to us we don't have the energy to have kids right now.

You are absolutely right so it's a little bit more complicated that but you basically got it right so there's two things first of all fat is not just an energy store that is also an organ right fat fat produces hormones we produce fat produces a hormone called leptin which affects appetite but it also produces estrogen so when women have very low levels of body fat their estrogen levels decline

and they're don't produce enough estrogen to have effective menstrual cycles so they become what's called a menoriac menoriac is is a is a just a fancy medical term for for loss of sort of normal cycling. It's been shown by many researchers former professor of mine Peter Ellison and their other researchers around the world.

And then in the world of women in Grazina, Jzezanska and Poland others have shown that you know our bodies are incredibly sensitive to energy availability for example women who are dieting they may have plenty of body fat but when they're dieting which means they're going to negative energy balance levels of progesterone which is a very important hormone for the menstrual cycle progesterone is produced in the second half of the menstrual

and it means the uterine lining so you can have implantation progesterone levels plummet they go down by you know 50% during the luteal phase that second half of the menstrual cycle thereby decreasing their ability to conceive. Women who are very physically active also there's a decrease in the amount of progesterone again during the second half of the menstrual cycle.

So what we have thinking about it though is that because remember what we evolved to do is to have as many offspring as possible and so our bodies also another way of thinking about this also is that whenever there's extra energy available the body you know it's an adaptation to say hey let's use that energy for reproduction so that's increased estrogen levels let's increase progesterone levels so we can increase our for quantity increase our fertility.

You know there's a bit of a balancing act yes it's a bit of a balancing act so so obviously you know exercise is not bad for women who are trying to conceive and and women who are but women who are sedentary and aren't exercising have a high levels of estrogen progesterone and that may that may be one of the reasons why physical activity decreases the risk of breast cancer so much so women who are physically active have like a 30 to 50% lower rate of breast cancer and a lot of that part of that has to do with the fact that their hormone levels are more normal because they're not going to be able to do that.

So we have a lot of levels are more normal because sedentary women have abnormally high levels but nonetheless it's the important point for what you asked is that our body is incredibly sensitive to energy right and so it knows that when energy levels are low when you're losing fat this is not a good time to invest because think about it pregnancy lasts nine months it's incredibly expensive and you're going to be spending months later nursing which is also very expensive maybe this is not a good time to invest let's wait until times are better than you know that you're not going to be able to do that.

Better than you know that this is a better use of your of your you know better time to get pregnant a better you can have a much more likely positive outcome. I was thinking about what you were saying through the lens of stress as well because stress releases cortisol and if someone is incredibly stressed I imagine they're going to have trouble with fertility as well probably for the same reason I guess it's like a line was running at you this is not good time to have a cortisol cortisol when

one of the things that cortisol does is it turns down everything that you don't need to do at that moment in time right because we evolved to elevate cortisol acutely you know for short bursts when you know when the lion comes into the room right. But but not over very very long periods of time so you know when when the lion comes into the room this is not a time to reproduce it's not time to spend energy on your immune system it's not time to do all kinds of stuff right just run right.

Make it energy available but situations where you have pre persistently high levels of cortisol chronic stress chronic stress that's what we call a mismatch right mismatches our conditions that for which our bodies did not evolve right these are novel environmental conditions for which we are inadequately or

imperfectly adapted for and that they cause the vast majority of the diseases and problems that we encounter today and you know taking exams is a mismatch having you know discrimination racism poverty these are you know all those sorts of things that elevate our cortisol levels for long periods of time those are mismatches you know if

you know fact the vast majority of the diseases that people have today apart from some infectious diseases but the vast majority even infectious diseases are mismatches because they come from humans spending more time with animals and you call all the a lot of the diseases that we you know infectious diseases that we have actually our diseases that jumped over from the animal world to humans to burky losses for example right that's a disease that

our body is not together isn't yet it's a it came after ferment the vast majority of diseases I would say so yeah I mean heart disease I mean look we when we look around the world and look at people who don't live in your modern western lifestyles they they heart diseases is very nonexistent there's a wonderful study of of a group of people in the Amazon and Amazon called the chamanine cordoculturalist foragers, right?

They have, there's like no evidence whatsoever of any coronary heart disease in these people. Some of the populations that we've studied, no increase in blood pressure. Back in the 1970s, some of the first studies that were ever done on the health of hunter-gatherers found that 80-year-old hunter-gatherers in the Kalahari had the same blood pressure as 20-year-old hunter-gatherers in the Kalahari.

And the compared them to English people and Londoners at the same time, and of course, by the time you're 70 or 80 in London, almost everybody's hypertensive, right? This is because of diet and physical activity and probably also stress. These are things that have changed in our modern world for which we are very poorly adapted. No diabetes? If it exists, nobody's diagnosed it. It's probably incredibly rare. But even a few generations ago, diabetes was rare.

I mean, diabetes is the world's fastest growing disease. Where I work in Kenya, in the area around the town, a city called Eldoret. When I first started working there, gosh, long time ago, you drive into the city, and you'd be an Eldoret. Now as you drive into the city, you pass by all these diabetes clinics. They weren't there before.

That's because diabetes is rising in Africa to that incredibly rapid rates, which isn't so surprising because diabetes in places like the United States and England aren't incredibly common. So they're like 12% of Americans have diabetes now. You said that this mismatch is responsible for most diseases. Doesn't that therefore mean that I'm most likely to die from a mismatch disease in my life? Yes. OK. Yes. The vast majority of us in the Western world will die from a mismatch disease.

The number one disease in the world today that kills more people than anybody, anything else, is heart disease. And as far as heart disease kills at least about a third of us. Cancer is number two. Cancer's, of course, our ancient disease. So not all cancers are mismatch disease. But many cancers are mismatches, right? Breast cancer, which is much more common in Western populations than in non-Western populations.

But heart disease is essentially as far as we're concerned non-existent until fairly recently. And now it's killing about 33% of us. You said a third, right? Yes. That's crazy. It's so crazy. That's the bad news, right? But the good news is because they're mismatched diseases, they're not inevitable, right? We shouldn't just say, all right, heart disease kills a third of us.

That's just because the amazing thing about heart disease is that diet and exercise can prevent a large percentage, if almost almost all of them, right? If people who live in environments where they don't eat a besogenic diets, diets that make people overweight, diets that lead to metabolic syndrome, diets that are atherogenic, that cause atherosclerosis, right? People who are physically active and stress is also an important role, plays a role in heart disease. Don't smoke.

Have vastly lower rates of heart disease. To the extent that this is a disease that doesn't have to exist. You said you're writing a book about diet and food. Yes. Why? The story of how the diets that we eat today and is actually a really fascinating story. But also because I think that we, if we take a more evolutionary approach to diet, we can, I think, do much better to thinking about how people make choices.

One important point to make is that today, when we finish this interview, I'm going to go home and my wife and I are going to, and my daughter and my mother-in-law are going to try to decide why we're going to have for dinner tonight. And we can go, we can eat whatever we want. We can go to the supermarket and there's like, you name it, right? Here in New York, there really is, you name it, right? We can go out to restaurants.

We can have Chinese or food or Japanese food or American food or French food, whatever, right? We have incredible choices to us. For most of human evolution or history, people never chose what they ate ever, right? They ate what was available to them. And now, with all this choice, we comes, comes bad choices, right?

And so I would like to help people figure out how, not only realize that these choices that we have to make or we're not really evolved to do, but also how to better understand what those choices are and what the complexities are of them. Because there are no such thing as a free lunch, right? Every choice that you make has alternatives and alternative consequences. And I think people oversimplified diet. People come up with simple ideas. You know, just do this. Just be a vegan. Just be a this.

Just be a that. There are no perfect answers. Do you think in some ways that our culture moved so much faster than our biology innocence? Because we're like super sedentary now. We just sit all day. We have these screens that bring us our food. The food is processed. And is this part of what's causing this sort of misalignment or the mismatched diseases that you call them is? Absolutely. Because evolution by natural selection occurs really slowly, right?

Every generation, people with genes that have given them adaptations that are better able to handle a particular environmental context do better than the next generation. So slowly, slowly, slowly, generation by generation, you get change. And that's true for every animal, right? At mismatches, not unique to humans, right? As environments change, some animals are better adapted to that environment than other animals.

And though those animals are going to be more likely to pass those genes onto their offspring. So mismatches are part of a natural selection. Every species, as environments change, is subject to mismatch, or as they move into new environments. The difference with humans is that we have culture. And culture has caused an acceleration of environmental change, right? Think about, I mean, just today, right? I have now in my pocket a computer, right? That I didn't have a few decades ago, right?

We have internet and email and all kinds of things, right? Just the last few decades the world has changed amazingly. Just think about the last few generations, the last few hundred years, the last few thousand years. So cultural evolution is so powerful and so rapid, it's so fast, it's so transformative that we have made our world so fast, vastly and rapidly different that our bodies cannot possibly keep up in terms of our biology. It's this mismatch.

This is difference between evolutionary biological change and cultural change that has heightened the kinds of mismatches that we exist. And then guess what we do, right? So we, let's say we, I'll give a very simple example, right? Until recently, nobody read, right? And nobody spent a lot of time indoors. And so myopia used to be extremely unusual, right? Myopia is having, is being near sighted.

OK. So if you go to, like there's a famous study where they looked in, in Inuit populations, right, Nalaska, and they looked at grandparents and grandchildren, the grandparents all had perfect vision. And the grandchildren all need glasses, or at least a large percentage of like 30% of them, right?

In various parts of the world, the, there are a number of people who are, are near sighted, has gone up in some parts of the world it's 50% in, in America and England, it's probably about 30% of us need glasses. But this is all recent. In fact, the first study this was done on the Queen's Guards, you know, or actually now they're the King's Guards, right? So you know those, they have the, their skin hats, I don't know what kind of fur it is on their head.

Anyway, they're the ones who stand in front of Buckingham Palace, right? There was a study done in there in the early 1800s, which showed that it was the officers who had a higher percentage, like a large number of the officers had to wear glasses. But the, the, the foot soldiers were all fine. And there was something about it, right, that, about the officers. And then people started studying them around the world. And, and then initially it was thought to be reading.

And now we know from more careful studies, that's really spending a lot of time indoors when you're young, that causes myopia. So we never evolved to do that, right? So we're more prone to myopia. But it's not a big deal because guess what? We just go to the optician and we get glasses and we can deal with it. And, you know, it's not, doesn't really have really any major effect on our, on our, on our health or our longevity, our ability to find a mate, et cetera. We all do just fine.

Can we undo it? Well, here's the thing. I mean, what we're doing in, no, myopia, you know, you can get lasx surgery and there are some things you can do very expensive. Most people can't afford it, right? But the point is that we're treating the symptom with, when you get glasses, you're treating the symptom not the cause, right? But it's okay, right? Because it's just glasses, right? The problem is that for many mismatched diseases, right?

When we are still, we're treating the symptoms rather than the causes, right? So, cancer, right? Or, or, or many forms of heart disease, right? You don't see a doctor in our, in our medical system until you get sick, right? And then you get pills to lower your blood pressure and pills to lower your cholesterol, et cetera.

But, but these aren't, well, those, some of them can be preventative, but, but, to a large extent, most of medical treatments are treating the symptoms diseases after they occur. And I'm, and of course, we should do that. We should alleviate pain, we should alleviate suffering, we should try to decrease people from, you know, dying from all kinds of diseases. But wouldn't it be better if we actually prevented those diseases in the first place, right?

We would have a much more effective medical system. So, what we're causing, in my opinion, kind of a new form of evolution. I call this dis-evolution, whereby we're treating the symptoms of mismatched diseases, thereby, enabling those diseases to remain prevalent, right? And in some cases, get worse, because, because we can now cope with them, right? So, people now get diabetes, we give them metformin or whatever, various kinds of drugs.

They get, they get heart disease, we give them various, you know, you know, pills to kind of keep them going. They get myopia, we give them glasses. Because all of these are things we should do, but wouldn't it be better if we prevented people from getting heart disease in the first place, right? Because this is one of the big questions I always have with evolution, and when we're talking about our evolutionary history, is, is all we still evolving?

And from what you said there, it sounds like we, in a way we are, but it doesn't sound good. It sounds, you say, de-evolution. Sounds like we're in some way. Dis-evolution, yeah. Yeah, I mean, I mean, there is, there is a little bit of selection going on. I mean, you can't stop selection. It's like gravity. It happens. But it's slow. What we, in Howie, I think it was James Nester that said, the way we chew impacts what our face looks like when we become adults.

If a baby's chewing lots of soft foods, when they grow up, they're going to have like a small jaw. Yeah, that's research I did, actually. Oh, really? I think you cited you. Yeah, so how you, you know, chewing affects the shape of your, you know, how are your, your, your jaw grows? And so it is true that we have smaller jaws today than we used to. The good news is it's not that bad, right? It doesn't really cause that much.

You may be able to, you have more likely to have malaclusions, etc. But, you know, you can, but we can go to the orthodontist and have our third muller is extracted, etc. I mean, we can, we can cope with that, right? It's not, that's not the worst thing, right? Of course, he thinks that it causes us to breathe through our mouths and all that sort of stuff.

But it's not the kind of disastrous sort of mismatch that occurs from, say, you know, well, this is controversial, but the evidence, you know, the vast majority of the evidence suggests that if you eat a lot of sugar, and you eat a lot of saturated fat, you're more likely to get heart disease. You're more likely to get plaques in your arteries, right? If you don't aren't physically active, you're, you know, do exercise or physical activity, your, your blood vessels start stiffening and you start

becoming hyper-tensive, right? These are all, these are all aspects of our environment that, that we, we have the potential to, to, to control better and to prevent disease. Do you think we've gotten into a bit of a bad habit as a society of just throwing a pellet, the problem? Yes. I mean, that's, that's the fundamental argument of, argument of making about disavolution, then, that, you know, it's just, it's expedient to treat the symptoms of a problem rather than its cause.

What's the problem with that? Well, because it's, number of reasons. One is, it's, isn't the best disease is the one that you never get in the first place. So, so we can keep people alive once they get heart disease. We can keep people alive once they get arthritis. We can keep people alive once they get all kinds of diseases, but they, but they're, but their quality of life goes down. And of course, we pay for it. We pay for it

out the nose, right? It's something like 70, 80% of the time when somebody goes into a doctor's office, that's for a preventable disease. 70, 80% of the time, right? That's a, an astonishing amount of money that we spend on our medical system on essentially mismatched diseases. It's bankrupting us, but it's also causing misery and it differentially affects people of, of low income and people who are, of suffer from discrimination. I mean, look in the United States,

right? Who gets the chance to exercise and eat fresh vegetables and high quality foods and non-processed foods? It's wealthy people, right? So, it's also, it's just unfair and unjust. You mentioned cancer. In what way, and how do we know that if that's a mismatch disease? Well, cancer is not completely a mismatch disease. I mean, you know, all species that are multicellular get cancer. Cancer is essentially a disease of evolution going wrong, right?

Natural selection going wrong, right? So instead of, you know, when you have many different kinds of cells in your body, when a cell becomes essentially selfish and starts to outcompete other cells because of mutations it gets, that's a cancer, right? So cancer is an outcome of multicellularity. Dinosaurs got cancer, right? We have evidence for bone cancer and dinosaurs. So it's, we're never going to get rid of cancer completely. But we also know that cancer is very much a disease

of energy, right? When people move to high energy environments, they're much more likely to get cancer. More food, meaty food. More food. Physical inactivity is a major risk factor for cancer. Insulin, for example, high levels of insulin, insulin, you know, promotes anything that promotes mitogenesis, which is mutation, you know, cells to divide is going to increase rates of cancer. Also, anything that increases the rate of, you know, a lot of the cells that could get cancer

or cells in our bodies that interact with the outside world. So our lungs are guts, you know, our colons where, you know, things from the outside world come into contact with them, skin exactly. Those are cells that often get cancer. So when we have chrycinogenous poisonous toxic compounds in our environment, those can elevate levels of cancer. So smoking, car pollution, et cetera, those can cause cancer. But also having lots of energy. So we talked earlier about when women

are physically inactive, their, their, their hormone levels shoot up, right? Because the body says, ha ha, more energy. Let's spend it on reproduction, right? And there's a tradeoff there, more in the higher levels of estrogen progesterone, increase the rate of breast cancers that, that occur. Because, because they cause more, more turnover on those cells in the, in breast tissue. And that's,

that's why those, those cancer rates are higher. So you can, there's famous studies which show that you look at women from Bangladesh who live in Bangladesh, women from Bangladesh who move to England, or Bangladesh women who are born in England and live in England. Where every, when, no matter how you, how you look at it, Bangladesh, she women who moved to England, their cancer rates go way up. The difference, a major difference is energy, you know, the diet that they have, the physical

activity levels they have. They're eating more, they put more weight. Cancer rates just shoot up, cancer. So if you actually plot GDP of countries against cancer rates, it's a almost nearly straight line, richer the country, the higher the rate of cancer. What about hunt together or women? Did they have less, um, ovarian cancer? Oh, hey, that's a hard thing to measure because diagnosing cancer requires some sophisticated technology. And to my knowledge, nobody's ever

done careful studies of cancer rates among hunter-gatherers. But most of us are pretty convinced that cancer rates are much, much, much lower among hunter-gatherers. But again, also the, the population sizes are tiny, so you can't really get very large samples. The amount of menstrual cycles you have is a major factor, right? So I believe, I hope I get

the numbers, right? Typical women today who goes through her entire reproductive lifespan, will have something like 500 menstrual cycles because of birth control and, um, and smaller families. I said 350 to 400 in your book. Does that mean it says? Okay, thank you. Okay. It's in the hundreds, right? Typical hunter-gatherer is going to have something like 50. 50. Yeah. In her entire life. Wow. And every time you go through a menstrual cycle,

your, your body is being exposed to high levels of these hormones, right? Birth control, and sort of modern family planning, which, you know, I'm not obviously, um, a post-roid, but it is another factor that has probably elevated rates of breast cancer. I didn't, I never knew that. I never knew that having more cycles reduced your treatment. Sure, because each, every cycle involves, you know, surges of hormones. That's what causes the cycle.

First, you have an estrogen surge, then you have a progesterone and an estrogen surge. Of course. That's, that's what happens across the menstrual cycle. And hunter-gatherer women would have been pregnant more often, more of their life. Well, yeah, they, typical, what we call a natural fertility population, a population that doesn't use birth control, women are most of the time pregnant or nursing, and they go through

short periods when they are doing neither and then get pregnant again. So, so the number of, and, and you don't, of course, have menstrual cycles when you're pregnant, and you're generally don't have menstrual cycles when you're nursing it until, again, it's your energy level. So, so, because nursing costs so much energy, that high energy demand of nursing suppresses a very infection. So, so, so, so, so, nursing women are often a menoriac. They're not cycling.

And that's not just a very incantement. That's breast cancer as well. Yeah, it's, you know, it's, yeah, any, any, any cells that are sensitive to estrogen and progesterone, those, those are the cancer, those, those particular kinds of, so often when you, you, you, you measure breast cancer, you talk about, you know, whether the, the cells are estrogen or

progesterone sensitive. I wanted to talk about how our body stores energy because I think that in part answers a lot of these questions around the things we're discussing about weight loss, about diet, about all those things we've talked about previously. I have a very loose understanding of this. So, please enlighten me, but I did go keto for eight weeks and I lost so much weight. It's, pretty crazy. It bounced right back, of course. Of course. Yeah. Because you mostly lost water.

Oh, really? Yeah. That's one of the problems with many diets. So, so fat is a, is a, fat is a wonderful molecule, right? It's, we tend to demonize it, but it's, it's, fat is life, right? Fat is a really important molecule. So, a fat is a, is a, a fat molecule has a back bone of something called glycerol, glycerin, right? It's a three carbon molecule. There's a carbon, carbon, carbon, and they're, they're little hydrogen sticking off. And to each one of those carbons is a

chain, a, sticks off a chain, what's called a fatty acid. So, so they're called triglycerides. They're three fatty acids on each glycerine. And, and there are different kinds of fatty acids, like they're saturated fatty acids and unsaturated fatty acids and we can blame all those, whatever. But the point is that these are each fatty acid stores a huge amount of energy because those long chains of carbon, what our body does is it cleaves those carbons into smaller units and gets, and we get

energy from that, from the bonds between those carbons. That's basically what our mitochondria doing, right? So, fatty acids, fats in general have store a huge amount of energy. They store twice as much energy as carbohydrates per unit mass. So, what we do is we, we eat foods that have fat in them or we eat carbohydrates and our livers convert them quickly to fats. It's not, it's, it's easy, right? So, that's why, you know, fat free diets don't prevent people from being fat,

right? Often with the help of insulin, but it's not the only hormone involved. We then, we want to store those if you're not burning them, right? Our body can either burn them or store them. So, if we're not burning them, IE, we're running or gesticulating, talking, etc. We're going to store them and we store them in, in special cells called adepocytes. Those are the fat storing cells. Our bodies have billions in them. You're born with billions of these,

but you only have so many adipocytes. You get them when you're young, when you're born, and that's it. That's the number of adipocytes you have for the rest of your life. And so, and so those adipocytes, so insulin, for example, helps potentially ate the movement of triglycerides, right? Which, which you want to break down and then you transport them into the fat cell and then you reassemble those fats in the fat cell, the, the, the glycerines and the fatty acids. You reassemble

them in the fat cell and they swell like a balloon. So, every little fat cell in your body is like a little balloon filled with, with fat. And, and it's there to be used. And then there are hormones, which then help us retrieve that fat when we need it, right? When we're running a marathon or, or just sitting around talking and without having a head lunch for a while or whatever. And so, you know, we store fat, we, we then burn fat, we store fat, we burn fat, we store fat, we burn

fat, et cetera. And that's normal, right? And as I, as we talked about earlier in this conversation, humans evolved to have an unusually high level of fat. So, a typical hunter gather male will have about 10 to 15% body fat, typical hunter female will have about 15 to 25% body fat. That's normal, sort of skinny human being. That's way more than most mammals, right? So, women had more. Women have more, right? So, women have a higher percentage of body fat, although actually,

women tend to be smaller bodies. So, the total amount of fat that men and women store is about the same. Women, of course, if you think about it, because they're involved in, they're the ones who have to pay for reproduction, and directly, either during pregnancy or, or nursing, that fat is especially important for reproduction, right? So, what happens is that, though, that fat is there, and it's like a bank account, right? It's energy that we store and energy that we use. And we start

in different places. Most of the fat that we store is what we call subcutaneous. So, underneath the skin, subcutaneous. But we also store fat that we call ectopic. That's outside of where it should be. Some of that fat is, and a lot of that ectopic fat is some of that's in our liver. We call that, so people have a lot of, so normal livers have just a little bit of fat in them. But if you have too much fat in your liver, your liver starts to malfunction. It's called non-alcoholic fatty liver

syndrome. You can have fat around your kidneys. That's what su it is, right? But too much fat around your kidneys, again, causes problems. Fat around your heart, fat around, so all that fat in your, in your abdomen, that we call that visceral fat. Visceral means guts, right? So, that gut fat is very problematic. And all, because when those fat cells get too big, so if you store a lot of fat beyond those sort of normal levels, as the fat cells get bigger and bigger and bigger, just like any

balloon, they start to rupture. So, you know, if you overfill a water balloon, it's going to break. If you overfill on a dipisite, it's also going to start break. And when it starts to break, it attracts the immune system. And the immune system comes in, white blood cells come, right? They think, so something's wrong. We have a, we have, we have damage here. And they start to produce molecules that trigger a system-wide immune response, right? And the fat cells themselves

also will trigger an immune response. The fat cells can produce the same kinds of molecules that are white blood cells produce. So, the white blood cells are produced molecules called cytokines. Cytophersel, right? Kind for, you know, enzymes that do something, right? And, and so the ones that fat cells produce, we call them adipocines. And like one adipocine that produces called, is a TGF alpha, right? You may have heard of. And that turns on your, it's like, it's like,

it turns up the dial on your, on your, on your inflammatory system, right? And it goes everywhere in your body. And you start getting inflammation, right? And that inflammation, for example, if it's those turns, see if you're, if you have inflammation in your, in your blood vessels, then that inflammation can help cause plaques to form in your arteries. If that inflammation

occurs in your brain, that can cause plaques in your brain that can cause Alzheimer's. If that inflammation affects receptor cells on muscles, et cetera, that can cause insulin resistance, which can cause diabetes. And the list goes on, right? So that, that chronic inflammation, which can be caused by too many fat cells that are over-packed, essentially, is, is why too much fat can, can be, can cause health problems. The keto diet and fasting, they, I saw someone say to

me, they're the day that keto is basically a form of fasting in a way. And are they, how do they help the body? Because people are pretty crazy and pretty keen on both fasting at the moment, but also the ketogenic diet. Well, fasting is when you go into negative energy melts, right? Which is how we spent most of our sort of evolutionary history, right? Well, you, how you spend part of every day, right? We, we eat. After you eat, you're in positive energy

balance. And then when you, in between meals, your energy balance goes down, right? Now you're in, you're burning now energy that you've stored. When you're asleep, you're in negative energy balance. So fasting is just a prolonged state of negative energy balance, right? Does that mean that would, it would reduce my chance of getting cancer? Could do. People are, are hoping that's

the case. I don't know how good the data are for intermittent fasting. Because if the surplus in energy causes cancer, then me being in that negative energy balance presumably will reduce my chances of getting these right. But then you have to go back into positive energy balance at some point too, right? You can't keep up negative energy balance. So intermittent fasting isn't necessarily a way to lose weight if you eventually, you know, replace those calories,

right? So what you, so here's a hypothesis, right? To which I cannot, I cannot prove. But I think that, you know, when you, when you exercise, right, you're also going to negative energy balance, because you're burning energy, you're not eating while you're exercise, these most people aren't, right? And, and your, and your body's turning, you know, turning on all kinds of mechanisms to, to cope with that negative energy balance, you're turning on all kinds of repair and maintenance

mechanisms. When you, when you, when you're going through intermittent fasting, you're basically doing the same thing, but less acutely. It's, it's a more gradual level. And I, and if you look at the, at the, at the genes that are turned on by exercise and the genes that are turned on by intermittent fasting, many of them are very much the same. And I think it's because you're basically turning on

genes that are responding to that negative energy balance. But, but I would argue that you're going to get more of a bang for your buck by exercising than just going through intermittent fasting. Both. Well, yeah, I mean, intermittent fasting might be a kind of an easy way to get some of the benefits of exercise without exercising. It might be. I mean, obviously we went, we, you know, there's nothing necessarily wrong with intermittent fasting. But I'm not sure that it has some of

the huge benefits that people claim. Now, keto diets are little different, right? So keto diets are when you're, you're basically avoiding any carbohydrates. And carbohydrates, the, the basic building block of most sugars is, is glucose, right? Glucose is the sort of simple form of sugar that are basically in starches. There are some other sugars, fructoses also, which is the kind of the sweet one. But when you basically stop taking in glucose, right? You're now basically taking in only fats.

And so instead of using glucose to fuel your brain and other cells in your body, you're now using what's called ketone bodies. These are, these are essentially, remember, we talked about how you, when you break those fats down into small little units, those are ketone bodies. They, they can be used as energy, but there are more of a kind of a backup energy source for our bodies than, than the primary energy source. So we, we use them, our bodies tend to use them when we don't have

glucose available to us. And does that mean the same sort of repair and restore mechanism kicks in? Potentially. No, I don't think so, because it's not negative energy balance. You're just using an alternative fuel in this particular point. Because a lot of doctors have sort of prescribed deketo diet for people that have like epilepsy to exceges. Right. And I don't think anybody knows, I'm not a neurologist, but I don't think anybody knows why keep, keep high ketone diets are so

beneficial for epilepsy, but it could be that they do. And I just don't know. And I'm, that's not my, it's not my subject. But anyway, there's a, there's a, there's a thought that if you just, you know, essentially keep your insulin levels low and rely on ketone bodies instead of glucose, you can, you know, do all kinds of miraculous things. For weight loss, if you look at the data, yes, it does tend to lead to rapid short-term weight loss. But the data don't, don't show it is very effective

as a long-term weight loss strategy. And I think your example, your own anecdotal account is, is sort of typical. Are we too coddled? Are we coddling our kids too much and coddling ourselves too much? And is that causing some of these mismatched diseases? Well, I'm not a psychiatrist or a psychologist. So I physically coddled. Oh, physically coddled. Um, stopping kids from doing anything that might hurt them or, you know, the risk of version.

Yeah, I think so. Yeah, I mean, the comfort industry. Absolutely. I mean, you know, I have all chapter in my book on comfort, right? We have this idea that comfort is somehow good for you. Like, where does that come from? Right? Um, comfort is nice, but, you know, I mean, who wouldn't rather be in business class than in economy, right? But, um, but, uh, is a comfortable shoe better for you, right? Is it, is sitting in a chair better for you than walking around or standing? Is it

better to take the stairs or take the lift or the elevator? Um, so comfort isn't necessarily good for us, but when we, but we now in a live in a world where we're able to have incredible levels of comfort and, um, and it's definitely not doing us some good because, you know, kids need to run around. I mean, every kid needs a good hour of physical activity a day to build a healthy skeletal system and to, you know, for all the other benefits that come from physical activity. So preventing our kids

from running around and doing all physical activity is definitely a problem. Is there any evidence that our kids are getting sort of physically weaker or physically? Oh, absolutely. Absolutely. I mean, we have data in the United States. I mean, we have this thing called the presidential fitness test, right? That was started. I think maybe it was Kennedy started. I kept some president a long time ago started it. So we have decades worth of data and kids today are, are, are less fit?

Absolutely. Uh, any ask any army recruiter, they'll tell you that fewer and fewer army recruits are, are physically fit and able to be strong in terms of bones and skeletal structures. Yeah. I mean, the rates of osteoporosis are going up. And, and one of the reasons for that is that, you know, loading our skeleton when we're growing up causes the skeleton to, to a crew mass to, to grow bone. If you don't, if you don't exercise, right? And especially weight bearing forms of

exercise, you don't grow as much skeleton. And then when you hit, you know, normally people stop adding bone around 25 to 30, right? So I don't know how old you are, but, you're 81. All right. So you're, yeah, that's it. You have no more bone to add in the rest of your life. You're going to start losing bone, right? But fortunately, you look like a reasonably fit

person who was very physically active. So you probably built up enough bone. So having a high level of bone when you're in your 20 thought, when you're 25 to 30, as you lose bone, that's going to protect you from falling below that threshold that's going to give you osteoporosis. But if you aren't physically active when you're young, you have less bone to start with. You're still losing through the lose bone. And you're going to be much more likely to fall below that threshold.

You're much more likely to get osteoporosis. And rates of osteoporosis are rising. Again, it's another one of these mismatch diseases that's rising radically throughout the world. Exercise also helps prevent bone loss because it, it, it suppresses the cells that, that essentially cause our bones to start being resorbed. So, so it's a, it's kind of a double whammy. You know, not, not enough exercise when you're young. You have less peak bone mass, not enough exercise

when you stay old. Your bones are going to lose mass at a more rapid rate. I was reading in your book that teen tennis players can become 40% thicker and stronger when they become older because they were using in the arm that they use. Yeah. So, so when you play tennis, right, the arm that you use, which is whacking the ball, that's getting more loading than the

arm that you simply use to throw the ball in the air. So, there's a symmetry. So, the humorous, the upper arm bone of tennis players can be like 40% thicker in the arm that they use to whack tennis bone. Just the bone. Yeah. It's, it's a beautiful experiment, you know, natural experiment in our body to show the importance of loading that, that loading causes your, your skeleton to respond because our skeletons are like other tissues in our bodies responds to demand, right? We match

capacity to demand. If you don't demand something of a tissue, it's not going to grow the capacity because otherwise it's going to be wasting energy, right? I know that about muscles. I know that muscles grow and expand, but I didn't think my bones had any say in the development of my bones. Absolutely. Yeah. Loading your bones is, is, is, is one of the factors that just we talked about it earlier. That's why people who eat harder food, you know, that's less processed grow larger

jaws, right? Our jaws have shrunk by about 6%. We showed by about 6% since we started processing all our food because we're just loading our, our jaws less, right? That's another example. Is there a consequence to this? Well, so when consequences, I increased rates of malaclusion, right? There's just not enough room for our teeth to fit into our jaws. So now we have to go to, we have to go to the orthodontist to get our wisdom teeth removed because there's not enough space

for them. Because, okay, so if I, if I just get my kid chewing hard food from the jump, then his wisdom teeth will be fine. It might be the case. Yeah. So, so, so the experiment, I'd like to see somebody do. Of course, it's unethical, right? It would be to randomize two groups of kids, have one group of kids, basically chew really hard, resinous gum for like all their childhood, right? Because you're not going to get them to eat like, you know, unprocessed hunter-gatherer food,

right? But basically, you can have them chew gum all the time. And then compare them to say their twins who don't chew that much gum. And let's see who, you know, see, see, see how much of an effect it has on their jaw growth. Pubety. Pubety, the age in which women go through puberty has changed quite significantly. Yeah. And I couldn't figure out why. It's, it's energy again, right? It's always, it's about energy. Remember, life is about energy, taking an energy and using that to reproduce.

So, so how much energy you have when you're growing up affects the rate at which you grow and the rate and the, and your ability to, to switch from growth to reproduction. So we have data, for example, from France, there's good data from, from hundreds of years in France. I'm not sure why the French have such good longitudinal data, maybe it's because of Napoleonic Army or whatever. But we can

show that, you know, 200 years ago, French girls were tending to go through puberty. They would start their menstrual, you know, they went through what we call menarchy when they start menstruating around the age of 16. Today, it's around 12, 12 and a half, right? And that's because of more energy. We see that in, in the area of Kenya where we do feel work, right? The, we're looking at the same population,

Collengean speaking people. And they're in the rural areas where, you know, they've hard lives, right? They're, they're working all day long. There's no machines, there's no electricity, there's not a huge amount of food. Girls, we go through menarchy about two years later than in the urban area, just, you know, 50 kilometers away where there's more food, there's more energy, there's more Coca-Cola, there's more, whatever. They, and we call that the secular trend, right? So that girls

are maturing earlier. They can reproduce her because again, what does natural selection want you to do? wants you to take an energy and use it to reproduce. That's what we're adapted for. So if you have more energy, we're, we're evolved to, to do it earlier. Every time I have these conversations, I realize that I'm sat in a chair for a living for sometimes three hours at a time. Today, I've been sat in this

chair for about seven hours. And I go, fact, this is not going to be good for me over the long time. If I do this podcast for the next 10 years, maybe I should just wrap it in here. I mean, it's been a good run. Does it, does it matter that I'm spending so much time sitting down? Is there any evidence that this is going to, you know, have an adverse effect? Well, so the evidence is that if you, so

people who sit more, it can be an issue. There's, but there's two issues. One is that if you look at the epidemiological data, what really matters is leisure time sitting versus work time sitting. So people who have, who sit a lot at work, but then also sit a lot in their leisure time when they're not at work. They're the ones who want run way more risk of disease than people who are just sitting

a lot at work. So that's one issue, right? So, so I think you're probably okay because I'm, I can tell you, you know, I know that you're obviously very physically active. You work out, et cetera. That's, that's going to help be very protective. But the other issue, and I think we talked about not my, in the previous interview, was sitting about. So, so how long you sit for a particular period is also very important. So we should be getting up every 20 minutes. You're going to be interviewing

Dave Reiklin in a few days. So Dave Reiklin published one of my favorite papers ever, who showed that the HODZA sit just as much as Westerners. They sit about 10 hours a day. But they get up all the time. Every, if you're in a HODZA camp, you know, there's babies running around. They get up to, we got the babies. They're getting around to 10 the fire. They're getting up all the time. There, nobody sits for a few hours and just like does what you and I are doing. And when you get

up, you're kind of turning on the metabolism of your body. You're turning on your muscles. It's like turning on the car engine, right? You're, you're kind of awakening all kinds of metabolic processes. And that seems to have a huge amount of benefit. So the key is, if you're going to sit, get up a lot. Go get up, go go pee, make a cup of tea, whatever, you know, interrupt your sitting. A lot of it. And of course, if you're going to sit at work, make sure that you're not spending,

you know, sitting in your car to get to work isn't good. And then you go home and you sit on the couch and watch television. That's not good. So, you know, make sure that those non-work periods of time are done involved in such a city. Is that why we've got so many of these random pains, joint pains, you know, we were talking about, you said, back pain is the, what'd you say? It's the number one medical complaint in the world, yeah, back pain.

And that surely is because of the way we've designed our chairs and our lives. Well, part of that is also just back strength. So we, you know, I'm sitting in this lovely, comfortable chair here and I'm resting my back against it. I don't have to use any of the back muscles, right? So we developed weak backs that don't have any endurance. So they're quickly fatigable, right? So, and actually the best predictor of whether somebody gets back pain is how strong

their backs are. And not just like, like, you know, acute strength, like from doing, you know, like one thing is it's how much endurance their back muscles have. Because, because, just think about it, like, I don't know at you, but like every once in a while I get back pain, right? I bend over to pick up a pencil or something like that. And I think it was picking up the pencil, right? But that's just the straw that literally broke the camel's back. It's, it's really the fact

that I just, it just happened to be the, the event that triggered it. But it's when my back is weak, right? That I'm just more likely to do something a little bit weird and then trigger something that causes a spasm, right? But having strong back muscles is the way to really to prevent back pain. If there's someone's just had everything you've said about these mismatched diseases,

there's a lot to take in, you know, there's a lot of different mismatched diseases. You said that if you're going to die from anything, it's basically going to be one of these mismatched diseases. Is there a conclusion? Is there an actionable conclusion about something maybe that I can change or do today? Or is there, there are philosophy you can lend me that is going to reduce my chances of getting one of these mismatched diseases, just like a broader philosophy toward the life?

Yes. I, well, two, I think there's two. The first is that understanding why we get particular kinds of mismatches helps us make decisions about how to use our bodies, right? What to eat, how to be physically active, how to sit. I mean, all the things that we've been talking about are result in action items, right? Let's get up more often, right? Let's not eat sugary, fatty foods so often, right? Let's, you know, let's try to avoid psychosocial stress, which is, you can't just,

you know, wave a magic wand and do that. That's a hard one. But we think that our life is normal. We think it's normal to live the kinds of, you know, everybody thinks their life is normal, right? We think the foods that we eat are normal, the kinds of physical activities that we do are normal, the clothes that we wear, the shoes that we wear are normal. Cars. Cars. All of that, right? And, but from an evolutionary perspective, they're not normal. That doesn't mean they're not good,

or they're, or that they're necessarily bad, right? But, but it's, it gives us a chance to pause and think and ask, you know, do we have to live with this, right? Or how can we modify the way we use cars and taxis and shoes? And, you know, we can, don't have to get rid of shoes, but maybe we be better off with more minimal shoes, especially for our kids. Maybe we'd be better off without, you know, processed foods that are have all the fiber, you know, removed and all that, you know,

that fat and sugar added and all kinds of other crap, right? Again, that's not engaged in a paleo fantasy and pretend that hunter-gatherers don't get sick or that, you know, hunter-gather, you know, what, if eating like a hunter-gather will make you, you know, absolutely healthy. That's not the way it works. But we have information that we can learn from our evolution and history that helps us

make better decisions. So that's part one. And point two is that we need to be really aware of this vicious cycle that we've created in our modern world, whereby treating the symptoms of these mismatched diseases are actually driving forward the system and making things worse. There's a reason that heart disease is going up in the world. There's a reason that diabetes is going up in the world. There's a reason that myopia is going up in the world, right? It's because we're,

we're creating novel environments for which our bodies are poorly or inadequately adapted. And then instead of preventing those causes, we're simply when we can treating the symptoms. And so we're not stopping that, you know, the fundamental problem from occurring. And thinking about it that way, if I'm a kind of modern sort of cultural evolutionary perspective, it's not a form of natural selection.

It's a kind of cultural evolution that's going on, but it's cultural evolution that's affecting our bodies. And thinking about that vicious cycle that we've created can help us stop the vicious cycle. As you'll know, if you've listened to this podcast before, I'm an investor in a company called Hule. I'm on their board and they sponsor this podcast. Daily Greens, which is this powder I have in front of me for those of you that can see, that gives you some incredible health benefits,

your energy, your concentration, your immunity is now available in the UK. For the 91 vitamins and minerals you get from it, the adaptogens, the daily green probiotics that are within this blend. And for the last year or so, all of you on this podcast that have deemed me about this product, to vast when it will be coming to the UK. It's now here. If you're someone that wants to get more greens into your diet, then I highly recommend giving it a go. Not only is it good for you,

but it tastes good, win-win. The product was so popular in the US that it sold out over and over again. I think that's what's going to happen here in the UK. So get your hands on it now. Just give it a try. Take a picture, tag me, DM me. Let me know what you think of it. And because I think it's going to become one of your staple products. If you're someone that's looking for a greens product in your life, then I really believe that this will probably become your staple as it has become

mine. Thank you so much Daniel. As you were speaking, I was just thinking about something we haven't discussed, but that is front of mind for me at the moment, which is the cosmetic products that are in my life. I spray all this geogen on my pores and I put all these chemicals on me, and there's a whole industry that are telling you to rub these creams into your face and all of

this stuff and alcohol in your mouth with mouthwash. And over the last three months, since we last were each other, I have really started to rethink about all these chemicals that I just assumed were all meant to throw down our mouths up our nose and you know what I'm saying? Yeah. Is there anything that you've learned, like any advice I need on that stuff? Just be skeptical. Skeptical. I mean, look, there's an entire world of people out there who's

trying to sell us stuff, right? And if you're particularly like you, you're clearly interested in how to live your life better. So I think you're especially vulnerable to people with the latest big idea, the latest new product, because you're a seeker, right? You're looking for this stuff, right? So you've got you, you're in their target, right? And you're I think more vulnerable. So I think being skeptical, now there doesn't mean that all products are bad for you,

but probably the most of most of them are, right? Or there's this they're not going to do much benefit and there could be unintended consequences. Everything has trade-offs, right? When you take some mouthwash, right, and kill the bacteria in your mouth, most of the bacteria they're killing probably are useful, right? Your microbiome, you have an oral microbiome. A lot of that's good for you, right? And it may have a short-term benefit of maybe making your breath

feel a little bit better, but it may have a long-term cost. I don't know, I'm not an expert in your life. Well, I've thrown it out anyway, because that was one of the things I looked at. I thought, okay, so I've alcohol, I don't drink anymore, but this mouthwash that I'm having is got all this alcohol in and I'm throwing it in my mouth every day, which is killing all the good bugs in my gut microbiome. And also even on our hands, we've because of COVID, we got into this culture of

sanitizing all the bugs off our hands. And it was quite scary because I think again through this lens of like, what is the more natural way to live? And this constant sanitizing of our hands and our children's hands and this fear of bugs. My girlfriend comes back from the gym and she rushes into the house, lathers on all this anti-biotic because she's been touching things that other people have been touching. When I go to the gym, I do that too. But yes, me too.

But look, you've heard of the hygiene hypothesis, right? This is, so you know, you have the same immune system. I have the same immune system as our great, great, great, great, great, great grandparents, right? I'm immune systems. You know, we all have these these really amazing immune systems that evolved, protect us from all those germs and worms out there, right? This is something I talk about in the book too. Now in this highly sanitized world, I still have the same

immune system, but now it's like, it's like, it doesn't have anything to do, right? The analogy I used is it's like, it's like a bunch of teenagers hanging out on the corner with nothing to do.

It's much more likely to get into trouble, right? And so people who grow up especially in more sanitized environments with dishwashers, without, you know, pets, without animals, etc., are much more likely to develop allergies and various kinds of autoimmune diseases because their immune systems are no longer busy defending them from the normal pathogens that are out there in the

in the world that we evolved to live in. And now we still have the same immune system. And now, you know, they're like those teenagers on the corner, they have nothing to do and they're mutt they increases the probability that they start to attack us. So that's why peanut allergies and various kinds of allergies and milk allergies and whatever and all these allergies are up on the rise because our immune systems are so unchallenged, they basically end up accidentally attacking

us because there's no pathogens to deal with. That's true of a wide range of autoimmune diseases. And so being ultra sterile environments, we think it's like the great, but actually, and during our pandemic, it can actually prevent you from getting an infectious disease,

but it also has costs. And it'll be interesting to see all those kids who were born during the pandemic, who didn't interact with other kids that much in nursery school or play school or whatever, who were wearing masks all the time, were getting all those creams, you know, those antibiotic creams, it's, you know, stuff. They might be more likely to get autoimmune diseases. We'll see as they grow up what happens to them. Daniel, thank you so much. All of your books are absolutely fascinating.

It's so bloody annoying because I could just talk to you forever. They're so brilliant, all of the books, absolutely brilliant. And I had so many calls after I last conversation, which I think is almost got 10 million downloads, which is crazy because it feels like it was a week, a couple of weeks ago, from friends of mine. I got a particularly hilarious call from a lady called Davina McCall, who is, she's been a TV presenter in the UK. She's one of the most famous people on TV in the UK

for 25 years. And she called me at 7am, right? And she calls me at 7am. She's, Stephen, I've just listened to the podcast with Daniel, even. She's, I'm running. She's, she's, she's like, get out my way. She's going to be blabbering. She's running down the street. Well, I'm very honored. Thank you. But I had so many phone calls like that and so many conversations like that because of that conversation. And this book is just a, gosh, the story of the human body.

It is essential reading. And as, as I've heard, it's being used in schools and education institutions. So I do hope that you continue to evolve and update the book with new science as and when it comes, because it's such an important book. Thank you again for the generosity of giving me your time. It's a huge huge honor. I say that. I don't say that lightly. We have a closing tradition on this podcast where the last guest leaves a question for the next guest.

You know the tradition. Okay. Ah, the question left for you is, for what would you be willing to die today? That's a very hard one. I mean, obviously, you know, it's a, it's a, I think we all think about that occasionally, right? I would, if it need be, I think for the people I really love and care about, right, for my, my daughter, my wife. And I think I would, I would certainly be willing to do a risk dying, you know, if it really had an enormous benefit for, for human kind, it would not

be an easy decision to make. And I've never been put into that position. So it's all theoretical. I think you wouldn't know the answer until you had to make that decision at the moment. Would you die for an idea? I don't think so. But I don't know. Interesting. But ideas can be powerful and important. Daniel Patelic, tough one. It's really tough and I'm just going to give it away a little bit here. But this is one part of

what we were discussing with the previous guest that was on the show. And he asked me this question. He asked me what I would die for and what I die for an idea, etc. And so I said I'd die for my siblings and my partner, my romantic partner. For some reason, I said I wouldn't die for my parents, but I think it's purely because I think it makes more sense for me to reproduce. And I have all the kids I'm going to have. And he asked if I would die for an idea. And as he left,

I thought about it more. And if you're saying the idea of a quality or these big ideas that would save lots of people's lives from suffering, I think I would die for an idea. He said would you die for your country as well, which is an interesting one? It depends what the consequence would be if I didn't. One can have these thoughts. You can think about it, the abstract, but it's totally different when you're actually confronted with a decision.

And what I don't know is whether or not what I just said would actually be the case in the moment. And that's why when he said would you die for your country, I felt like I can't answer that. It would be disrespectful for those that are dying for my country right now. But people do. Yeah, and people do. And I, for me to just sit here in this podcasting chair in this hot studio, and go, yeah, of course I would. But I'm absolutely not doing that. And if they hadn't,

we might not be here today. That's true. Daniel, thank you. My pleasure. Thank you. Do you need a podcast to listen to next? We've discovered that people who liked this episode also tend to absolutely love another recent episode we've done. So I've linked that episode in the description below. I know you'll enjoy it.