Harvard’s Exercise Professor Debunks The Biggest Exercise Myths | Prof. Daniel Lieberman

Oh, I'm going to get in real serious trouble for this one. Look, I mean, the given moment of time, you have in your bloodstream about a teaspoon of sugar. And if you get up to a teaspoon and a half, that's actually toxic.

Well, in a kind of paradoxical kind of cruel twist of fate, getting fatter from sugar makes you actually eat more.

A vicious cycle.

It's a vicious cycle. Exactly. I mean, the evidence is very clear that we're going to what scientists call the physical activity transition.

How do you explain that transition?

Well, it's machines, right? It's the change in lifestyle, right? In our evolutionary history, we were selected to become extremely physically active. You take me and you put me in the North Pole, I will not be very well adapted to handling the cold environment, right? By the same logic, my body is not very well adapted to not being physically active on a regular basis.

Our lifespan is being way above the paleative wall. So,

Well, actually, so that's another misconception that people have. So, there's a distinction between lifespan and health span. So, how long you live is not necessarily how long you're healthy.

What do you think or what can you say that it's your mission?

Look, here's how I would think about it.

Well, okay, that's fascinating and I want to dive into that even more.

What is the biggest mistake that people make when they exercise?

Um, just not exercising. I mean, um, so for example, um, one statistic I love to repeat, um, is that if a woman gets about 150 minutes of exercise a week, that's 21 minutes a day of just brisk walking, she can lower her lifetime risk of breast cancer by between 30 and 50%.

Wow.

People who get about that much exercise can lower their lifetime risk of Alzheimer's by 30, 40%. And more exercise has even bigger effects. Why don't people know this, right? That's what I think is most astonishing that that we all know that exercise is good for you. I mean, that's like, you know, you don't have to have a professor tell you that or a doctor tell you that, but people, including a lot of people in the medical world, don't know how much benefit it is and also why it's so beneficial.

Wow. Can you please elaborate more about the benefits?

Well, I mean, it's I could go, we could go on for hours and hours and hours and hours. We could go for days. So, I mean, you know, I mean, there's probably no system of your body that isn't affected by physical activity.

Yeah. But you said that the example that you gave with a woman is about walking,

Right?

So, walking counts as physical activity just as much as lifting weights.

Well, I mean, there are different kinds of physical activity, right? And they have different benefits, right? And different costs as well. Nothing is for free and exercise is no different, right? There are costs and benefits to everything. But, um, in general, um, in the exercise science world, people divide, uh, physical activity between aerobic physical activity or what's often called cardio, and strength physical activity or resistance physical activity. And obviously, it's a, it's a somewhat false dichotomy, right? Or it's an extreme dichotomy because lots of exercises or physical activities involve a little bit of both, right? Like, if I, like I like to do some rowing. I, I'm, I enjoy rowing a few times a week.

Oh, really?

Rowing? Yeah. And rowing is, um, is both aerobic but also resistance, right? Um, uh, whereas if I just lift weights, that's pretty much just resistance. Although you can do, um, what's called circuit training, you can do weightlifting in a way that also has an aerobic component. So, there's no, it's a little bit of an overly generalized, you know, overly kind of the distinction is not complete, but, but, but they have different effects. So, aerobic physical activity has, of course, lots of effects on your cardiovascular system. It also affects metabolism. It affects, you know, you know, cells throughout your body in all kinds of ways. Uh, strength physical activity is more localized to muscles, but also has effects on metabolism in different ways by, say, increasing muscle mass and, and, you know, all of these different kinds of physical activity have different effects. And so, there's no, it's hard to, you know, generalize in a simple way, but the important point is that most forms of physical activity have wide-ranging effects throughout your body on almost every single system of your body and, um, and, um, and they, and, and that are by and large extremely beneficial.

Well, okay, that's fascinating and I want to dive into that even more, but let's just say you are one of the world-renowned experts of human physical activity in evolution in science.

Some people think that maybe. Yes.

Yeah, I do. So, thank you so much again. So, where does the evolutionary science comes into this equation?

Well, I mean, evolution is important because it explains why things are the way we are, right? We weren't designed, we weren't engineered, we evolved. I mean, not everybody believes that, but, but they, that that's not a scientific explanation. I'm a scientist, right? So, science, you know, evolution is, is a, is the science, scientific theory of how and why we are the way we are. And, and if you want to understand how the why we way we are, you need to understand that evolutionary history, right? And, um, and humans are so, all animals evolve to be physically active, right? I mean, u, they have to move around to to get dinner and move around in order to avoid being somebody else's dinner and that sort of thing. But humans had special selection because we evolved from, uh, apes, right? We evolved from chimpanzee-like creatures. And chimpanzees and most apes are actually extremely inactive. They, um, they spend about half as much energy being physically active as you would expect for an animal their size. Chimpanzees walk maybe like two to three kilometers a day. They mostly rest and eat. I mean, they don't really do very much.

They do a lot of chewing.

Yeah. They spend half the day chewing and half the day digesting. They don't. They're very inactive creatures actually. And so are gorillas, so are all the great apes. And we evolved from them, right? And during our evolutionary history, we went underwent serious selection to become hunter-gatherers. And hunter-gatherers are extremely physically active. Typical hunter-gatherers walk 10 to 15 kilometers every day. They dig, they climb, they, you know, they do all kinds of stuff right without machines. And so our evolutionary history, uh, in our evolutionary history, we were selected, we were, to become extremely physically active. In fact, we're more physically active than most mammals of our size, about 30 to 40% more, more physically active. And, um, and so, but that physical activity has had effects on our biology. And so from an evolutionary perspective, if you suddenly become as inactive as a chimpanzee, which is what basically a lot of humans are today, that's what we call a mismatch. Um, a mismatch is when you mismatch diseases or mismatched conditions are are conditions or diseases that are more common and more severe because our bodies are inadequately or imperfectly adapted to, uh, that condition. So, a simple example would be jet lag, right? If I get on an airplane and I fly to, I don't know, somewhere like Asia, right, on the other side of the planet, my, I, I will be poorly adapted to that time change, right? We all know jet lag, right? Um, that's a similar example. Or if you take, you take me and you put me in the North Pole, I will not be very well adapted to handling the cold environment there, right? Um, by the same logic, I'm actually, my body is not very well adapted to not being physically active on a regular basis because when I'm physically inactive, I don't, um, I don't turn on all kinds of repair and maintenance mechanisms that keep me healthy. I end up allocating more energy to body fat, to, to reproductive hormones, etc. All kinds of things happen that that can cause me to be more likely to get sick and, and, um, and die young.

Yeah, that's fascinating, this mismatch. And how do you see the the current statistics, if you have some, about how does it spread around the world? Is it, is it fair to say that like we are going backwards towards being more like a chimpanzee in the physical activity side of things?

Oh, I mean, yeah, they, I mean, the evidence is very clear that we're going to what's what what what's what scientists call the physical activity transition. So, we're studying this for example in, in Africa, right? Where my, my colleagues and I have been looking in Rwanda and in Kenya and places like that, where we're looking at at how physically active people are in, in rural areas. These are farmers who, who, who, who, you know, produce their own food without the help of machines. They have no running water. They, you know, they work really hard, right? And then, um, and as, as Africa is modernizing, as Rwanda, for example, is modernizing, people are moving to the cities and all of a sudden they have supermarkets and they have, uh, taxis or, you know, they have these motorcycle taxis where people take all over the place and, and they have, um, and they, you know, they don't have to walk up and down every day to, you know, get food and get, they, if they want water, they just turn on a tap. Whereas in the rural area, if you want water, you have to go and go to a stream or a, or a well or a, or a spring and fill up your water container and you have to carry it home. It's a huge amount of effort, right? Now, you just turn on a tap and water just comes. It's like magic, right? And so, we can show, um, you, we can measure that people are becoming way less active. So, typical person in Rwanda, for example, um, uh, the farmers that we've measured are actually some of the most physically active people in the world. They're spending huge amounts of energy every day just moving around. Some of them taking 20,000 or more steps a day. We actually had one woman who was taking 40,000 steps in a day. One, one woman in our sample. I mean, that's like a marathon, right? Um, and it's all up and down, right? And then in the city, the Rwandans in the city of Kigali, which is the capital city of Rwanda, are as inactive as your average American. So, this is happening overnight. It's an instant transition, right?

Why? How do you explain that transition?

Well, it's machines, right? It's the change in lifestyle, right? You have, if you go from being a farmer without electricity and without trucks and tractors and cars and and plumbing and electricity and all of a sudden you live in a city, you, you, you know, all of a sudden you don't have to be as physically active and, and, and unless you have a, unless you decide to go for a run every morning, um, or, or do exercise, right? Um, you will have many fewer steps a day, you'll just be, you, you'll just be less physically active. And, and I mean, it's not too complicated.

Of course. Yeah. The thing while reading your book, the thing that astonished me the most is this mismatch. It's the fact that we are not adapted in many, many ways besides physically being active. It's also the way we consume media and everything around us makes our, uh, ancient brain go nuts, perhaps. Um, I, I wanted to ask what's the most alarming thing that you think that you see about this mismatch?

We're mismatched to eating huge amounts of sugar. We're mismatched to social media. We're mismatched to to lawyers. We're mismatched to, you know, most politicians. We're, I mean, I could go on, right? I, I'm sure anybody watching this or listening to this can come up with their own set of mismatches. It's not a very complicated idea. Um, but, you know, we also need to be careful about mismatch. It's not just because something is new doesn't mean it's a mismatch. And just because something is old doesn't mean it's good for us either. So, sometimes people take the, the theory of mismatch a little bit too simply. It's a, it's a scientific hypothesis, that we have to test. Like, for example, oh, I don't know, refrigeration. Um, you could argue that, you know, I mean, you know, refrigeration is a completely modern thing. We're a mismatch to it. And I would, I would consider quite the opposite. I think I'm very glad I have a refrigerator. My food doesn't go rotten. Um, um, antibiotics are another interesting example. I mean, to some extent, they can be mismatches. So, people can get sick from antibiotics. We can have negative effects on our microbiome. We can, you know, there can be, you know, negative consequences to antibiotics. But a lot of us wouldn't be alive today, uh, if it hadn't been for the invention of antibiotics. So, so, we need to be careful about about overly simplistic, um, it's what's often called the naturalistic fallacy. The idea that if something's, this is the problem with a paleo diet, right? If you know the idea that we, since we have evolved to eat paleolithic foods, we should, it, they must be therefore best for us.

Yeah. The the thing is that I think most people, if they have anything to reject to the these ideas, is the fact that our lifespan has been way above the paleolithic world.

So, well, actually, so that's another misconception that people have. So, it turns out that, um, hunter-gatherers, uh, tend to live about seven decades. Um, and it's, it was after the origins of farming that lifespan started to shoot down, right? And, and, and we need to make a distinction between, uh, um, life expectancy at birth and median longevity. So, so, um, it turns out that, you know, a lot of hunter-gatherer children die, a fair number die early on, right? But after you correct for infant mortality, they tend to live to be about 70 or sometimes up to 80, right? So, and which is actually not too far off from, from, from western countries. Um, so, once you correct for infant mortality, actually, we're pretty much, you know, we're a little bit, we're doing a little bit better than hunter-gatherers. Um, it was in the origins of farming that people started dying off like in droves because when people started farming, they started living in villages with animals, you know, rats and mice and living next to their their sheep and their goats and their cattle, which gave them diseases. They were also, because they were sedentary and living impermanently in villages, they were surrounded by their by their filth. So, there's, you know, all kinds of, um, uh, sanitation problems. That's when people's lifespan went, went down. And it's only with the invention of sanitation and various other, which has had really the most effect on human, uh, life expectancy, that people, we've gone back up to where we were and now we're a little bit better. But the other thing you need to understand is there's a distinction between lifespan and health span.

So, how long you live is not necessarily how long you're healthy, right? And so, I think, and in the, before modern medicine, your health span determined your lifespan. There was no doctor to keep you, you know, alive after you got really sick, right? Um, and so, if you look at the effects of, uh, diet and physical activity, they, they, they have strong effects on health span, which then have effects on lifespan, but they're, they're contaminated in a way by modern science. For example, if I have heart disease or atherosclerosis or hypertension or whatever from my bad lifestyle, I can take all kinds of pills that can keep me going for longer than I would have been the case, you know, you know, a few hundred years ago. So, so, so, so the average American, for example, today has an a lifespan of about 78, 79, but the average American's health span today is about 63. So, the average American is living 15, 16 years after their in chronic illness. That's the average. So, that means there are plenty of people who are have more.

It probably has something to do with retirement as well. Am I?

Well, I mean, it's diet and physical activity, right? It's, it's, and, and smoking to some extent. You know, those are the things. Those are the key. Look, if you, if you know, I mean, I mean, you don't need me to tell you this. Everybody knows this already. It's well known. You know, if you don't smoke, if you don't drink too much, if you exercise and eat an a reasonable diet, you're much less likely to get a wide range of diseases, um, that, that, um, that of course are often chronic diseases. Think about heart disease and, and, um, you know, diabetes and, you know, some cancers, etc., that can last a long time and, um, um, and just those, just few changes to your lifestyle can have huge effects on your health span, hence your lifespan.

Yeah. In this matter, I just read a book. I'm, I'm sure you've read it as well. Meditations by Marcus Aurelius.

Oh, yes.

Yeah. He buried six sons before he had an heir. So, it's, he tells us a lot about the ancient world.

Yes. Well, Marcus really, and he was the emperor of Rome, too.

Yeah. And he was the emperor.

Yeah. Life, life back then was, because of especially because of contagion, because of infectious diseases, was much more, you know, it doesn't matter whether you're, you're an emperor or a, or a peasant, you were much more likely to die, especially when you're young.

Yeah. So, this is infant mortality, which is the cause for the way we see lifespan being.

Correct. Yeah. So, so, if you're looking at, you know, really, it's important to correct for infant mortality when you think about about the effects of environment on, on your health.

Yeah. So, I, I want to go back. You mentioned sugar and sleep, uh, which are a big components of health. Can you please elaborate more and why modern people are, you know, I would say if there's any one, um, food that's causing, um, people to become sick, it's the, it's the increase in sugar and also refined carbohydrates. So, white flour, things like that. And, and we know why it's not even a, it's not even that, you know, it's not that complicated. I mean, we evolved to eat carbohydrates, but we evolved to eat foods that were whole and with lots of fiber in them, but now we remove the fiber from our food, like we mill our flour, so the, so the, the, the fiber is gone and actually a lot of the nutrients and the protein is gone, too. Or we, we have sugar. Now, back in the old days, right, like how would you get anything sweet? You, you could have honey or fruit and most fruits aren't that sweet, right? And you also can't eat that much of them, right? So, and now, of course, today people have gone from eating, you know, a few, maybe a kilo or so of, of sugar a year to, to, you know, like 100 kilos a year because it's added to everything. It's added to our, to our drinks. It's added to our food. It's, you know, we bake with it. We make all kinds of foods with sugar.

They took an Advil in in the United States and it added sugar on it. I was amazed.

There's sugar on the Advil. I didn't know that. Okay. Yeah. Well, I mean, you know, helps the medicine go down, right? So,

Uh, we, we add sugar to everything. And, um, and what sugar does, among other things, is that it, um, it affects our metabolism. So, it affects our digestion. So, when you have foods with a lot of sugar without much, um, fiber, you digest the sugar really rapidly. That causes a spike in your blood sugar level. That blood sugar then, um, overwhelms your system. You end up producing a huge amount of insulin to to get that sugar out of your blood. Do you know, at a, at a given moment in time, I, I've, I've done the calculations and other people have done it as well. But at a given moment of time, you have in your bloodstream about a teaspoon of sugar. And if you get up to a teaspoon and a half, that's actually toxic. So, our, our bodies have to regulate the amount of sugar in our bloodstream really precisely. So, if you have too much sugar in your bloodstream, your body immediately gets produces insulin or tells your, to your, your pancreas to release the hormone insulin to get that sugar out of your bloodstream. But if you have a lot of sugar really fast, which is what happens when you have, you know, processed foods, you, you overproduce the insulin. So, then you have a sugar crash. So, that does two things. One is that makes you hungry. So, then you end up eating more. So, then you keep eating more and more and more and more. But also, that sugar goes into your fat cells. Your fat cells, your fat cells convert that sugar into fat. And, and we're, our, our metabolisms are elegantly and beautifully adapted to convert excess energy into fat. And, but as fat cells swell, guess what they do? They suck up more sugar.

So, it makes you hungry. So, in a, in a kind of a paradoxical kind of cruel twist of fate, getting fatter from sugar makes you actually eat more.

Um, so,

A vicious cycle.

It's a vicious cycle. Exactly. So, um, so, uh, so sugar is really a major, there's just, I mean, it's, there's a lot of data to show this. Sugar is a major, it's not the only, but it's a major component of why so many people around the, the world today are, are, are gaining too much weight or either have obesity or, or overweight. Um, it also causes a range of other, uh, metabolic problems. Um, so, um, so we pay a price. So, that's a mismatch. We're clearly not adapted to eating foods that are filled with sugar with, with no fiber.

Yeah. In the case of, um, obesity and diabetes, do you think that the, the epidemic of it is caused by too many, too much sugar that we consume, or is it the other way around?

Oh, well, I mean, there's no one cause to the obesity epidemic. I mean, you try to oversimplify it, you're going to get it wrong. But there's no question that one of the components to obesity is, is that we have more, more food, you know, we have way more sugar in our food, way more processed food that also has a lack of fiber. It's not just the sugar on its own. It's the combination of sugar plus fiber because when you eat foods that have fiber in them, fiber slows the rate at which you absorb and digest sugar. So, it enables your body to handle that sugar much better. So, and also, you know, we have junk food which also has more fat in it and fat has calories, you know, we, we, we have very cheap processed food which probably get us to, you know, encourage us to eat more than we might otherwise eat. Um, we're less physically active. I mean, there's, there's many, there's many, you know, our microbiomes have effects. Um, obesity. There's many, many, many causes to obesity and, and, and, and it's never a good idea to try to say it's just one thing because it's never just one thing.

But, but is it fair to say that, uh, it's a, it's a feature, not a bug in our evolutionary biology? If we, you take a person from the paleolithic world and you put it in this environment, obesity is a given outcome.

Well, I mean, there are lots of people today who aren't obese. I mean, I'm not obese, right?

Yeah. But you need to work perhaps for it.

Yeah. Well, I mean, there's also variation. Some people have higher metabolisms. It's complicated, right? But,

Excuses for trying to simplify things.

Well, but that's part of the problem is that we try to oversimplify complex things and then people get skeptical about about about because, you know, we, we say, you know, like my, you know, we all know people who eat a lot of sugar and they're fine, right? So, it's, it's complicated, right? Uh, like, for example, in, you know, I work in, in Kenya, there are athletes in Kenya, right, who eat vast amounts of refined carbohydrates. I think by one study, like 75% of their diet is, is like simple carbohydrates because they're, but guess what? They're running, you know, 150 kilometers, 200 kilometers a week, right? So, and that changes not only how much energy they're spending, right? You know, they're spending a lot more energy than, than, than, than I am just moving around, obviously, but it also affects their, their hormonal response to the same food. So, people who are very physically active, if you take two people who are have different physical activity levels, one person who's more physically active, one person who's less physically active, you give them the same food, the person who's more physically active will have a less of an insulin response to the same food, because it changes our, our, our hormonal response. So, it's, it's complicated. There's no simple, simple, simple answers, but, but there's no question that sugar and refined carbohydrates have had a massive effect. I would say the dominant effect on, on the increase in obesity.

Yeah, thank you for correcting me and, uh, I'll try to not simplify the complicated things. Uh, but you mentioned metabolic diseases. How about cancer?

Well, cancer is complicated, right? Again, there's no one cancer. There are many kinds of cancer. I mean, even you could take a cancer of one organ and you can actually, it turns out, you know, there, you know, it depends on the mutation, you know, even we may say liver cancer or gallbladder cancer or, you know, pancreatic cancer, but, but actually each person's cancer can be different depending upon which genes are involved in that cancer. So, let's just remember that. But, but cancer, um, can have many causes, but one of them is energy. Cancerous cells are, are sugar-hungry, right? They, they actually prefer to use sugar versus fats to, for, for metabolic reasons. So, high sugar diets can increase cancer simply because, um, there's more, they can, you basically, you're feeding your cancer cells. Secondly, uh, cancer can be affected by hormone levels and people who are very physically inactive, um, can have higher hormone levels than people who are physically active. Uh, that, for that's an interesting story there. Um, insulin affects cancer rates. So, people who have more sugar have higher levels of insulin. Higher levels of insulin is an, is what we call an anabolic hormone. It turns on, it makes your cells do stuff, right? It's a, it's a, it's a, it's a, it's a growth hormone. And so, more growth means more mutations, right? Um, so, so higher levels of insulin are associated with higher levels of cancer. Um, body fat, fat, um, more fat causes cancer because fat cells produce, uh, molecules called adipokines, which, um, um, are, um, are, cause inflammation and inflammation is when your immune system starts to basically attack yourself, and that can cause cancer. So, lots of factors, lots and lots and lots of factors increase cancer rates, but many of them, as we've just, you probably just been following what I just said, many of them result from changes in our environment. So, cancer is not a, a new thing. Cancer's been around for millions, probably billions of years, but rates of cancer go up with socioeconomic status. As countries become wealthier and more and more people are obese and more people are eating higher, higher, you know, sugary diets and, and so on and so forth and are less physically active, cancer rates go way up. So, we can see this, uh, across the world as, as, as cancer rates are very high in, in industrialized countries, um, but they're, um, but their other places are, are catching up as they become wealthier and more industrialized. Cancer is a disease of energy.

Yeah. And so, what are the statistics about the places that you explored about the ancient world?

Well, I mean, it's very hard to get cancer rates from the ancient world because there was no, di, you know, there were no, you couldn't go to somebody's hospital and diagnose somebody with cancer. So, we have, we don't have a great idea about cancer rates, uh, in, in, in the, in the paleolithic, obviously, or even actually up until the modern medical world, but we have some data. So, for example, in, uh, in Verona, Italy, there was a, a, a famous physician named Riggoni Stern, who, who actually cataloged, um, rates of breast cancer in, in the hospital there and figured out that, um, that, uh, it was much more common, for example, among nuns, religious women, right, who, of course, were not having babies, than among non-nuns, for example. And he was also showing that cancer, you know, so, so he had, like, we have some data from. And, you know, even if you correct for the fact that he wasn't able to diagnose cancer as, as, as well as we can today, we can show that cancer rates in places like Italy have gone way up. Cancer rates are higher among women who are, um, who have, um, have fewer babies than more babies. And that's because of hormones. Every time, um, a woman has a menstrual cycle, she has a big, huge estrogen and progesterone surge. And the average, uh, hunter-gatherer, because hunter-gatherers have, you know, get pregnant, have a baby, nurse that baby for a while, get pregnant again, etc. They maybe have five, five or so babies over the course of their lifetime. Modern women who are on birth control or whatever, average, so the average hunter-gatherer has maybe 100, 150 menstrual cycles in her lifetime. The average Western woman has about 400. So, more than twice the number of cycles. And of course, every time you have a menstrual cycle, you have this huge surge of estrogen and progesterone. And that, those are mitogenic hormones. Those cause cell division, right? Which increase your risk of cancer.

So, that's just one of just many, many, many factors, right? But cancer is really ultimately a disease of energy because it's about, uh, cells getting more energy to make copies of themselves and they start out competing, uh, uh, uh, other cells in your body. That's basically what cancer is.

Wow. Uh, this is, uh, really the, the, the thing that you just said about the women, the, the, the difference between modern women and ancient women is fascinating, but,

Well, let me give you another example. So, there's a study that shows if you looked at breast cancer rates in women from Bangladesh who moved to England, women who were born in Bangladesh, stayed in Bangladesh, or, and women in who are of Bangladeshi ancestry who were born in England and grew up in England. Right? So, there, these are all, um, uh, women from the same population, but in different environments. And, and being in England just being in England alone increased their risk of breast cancer enormously. Right. So, it's the pop, it's the environment. You know, we often spend a lot of effort and time thinking about the genes involved in, in various diseases. You know, I mean, there are all these studies on the genes involved in diabetes and heart disease and this, that, and the other, but there's an expression in biology. Genes load the gun, but environment pulls the trigger. And, and it's, these are gene-environment interactions in which it's the environment that's changed. And we need to pay more. It's not that studying genes isn't important, but you're, you're not, you and I can't change our genes, right? We can change our environment.

Yeah. It makes you hopeless.

Yeah. But it shouldn't. And so, we should, we need to spend more effort and more money and more resources worrying about our environments because, um, you know, the genetics isn't unimportant, but it's the, the environment is, is really much more important than we often give it credit.

Yeah. What about sleep?

Well, I mean, everybody knows, I mean, I don't need to tell you that sleep is important, right? Everybody knows that sleep is important. Although I think we sometimes, uh, again, oversimplify. So, I'll give you an example. Uh, there's a standard story that people say, which is that, you know, Edison robbed us of sleep, right? That, you know, when we invented, um, you know, electricity and we have lights and TV and now we have cell phones and, and all these sorts of things that keep us awake, that that we're sleeping less. Turns out, a bunch of researchers have gone to parts of the world where there are, there's no light bulbs and no TV and no cell phones. So, studying people who are, you know, still off the grid, um, living, uh, you know, in, like, you know, we're talking about in the Amazon, in, in the Kalahari desert, uh, in, in, uh, in East Africa, the Amish, for example, you know, uh, various populations where, where people are not, you know, contaminated as much by, by modern, you know, environments. Guess what? How much they sleep? They sleep about six and a half hours. That's the average. So, the idea that, you know, we used to all sleep eight hours and that, and that, you know, the modern world has, has, has, has caused us to sleep less, turns out to be a fiction, um, or exaggerated, um, which is not to say that to trivialize sleep. Um, if you don't get enough sleep, um, all kinds of problems happen. But, but what's the optimal amount of sleep? It's kind of complicated. Probably around, you know, most big studies find about seven hours is about for most people, about optimal, but it's a very complicated phenomenon because it's variable from person to person. So, what's best for you might not be best for me, and certainly, you know, teenagers sleep more and old people sleep less.

And furthermore, remember, we didn't evolve to live to be a hundred.

We evolved to have as many offspring as possible, right? So, so what's optimal for lifespan and health span might not necessarily be what natural selection cares about, which is how many offspring you have.

Yeah.

And, you know, maybe sleeping less might be bene, you know, who knows? It's complicated. So, so we, we tend to kind of exaggerate sleep. The other thing we do about sleep is that we make people really nervous about it. Right.

The reason I entitled my book exercise, that we make people exercise, make them, you know, nervous and upset and feel judged and and upset about exercise. Well, we do the same thing with sleep, right? What I call the sleep industrial complex. Like, we, we tell people if you're not getting eight hours, there's something wrong. And so people, they buy pills to make them sleep. They, you know, they, they get special mattresses. They, you know, cover their windows so there's no light, etc. You know, if that makes you help, helps you sleep better, but what a lot of this does is it makes people stressed about sleep. And guess what stress does? Stress elevates levels of cortisol. Cortisol is your arousal hormone. It's cortisol which prevents you from sleeping. So, when things are really bad, right, like when, you know, during war or famine or, you know, political unrest or whatever, people's cortisol levels go up and they sleep less, right? So, making people stressed about sleep is exactly the worst thing to do to help them sleep more. And, but it's very profitable because you can make them buy all kinds of stuff. Look, I often say to my students, like, "How many of you sleep on airplanes?" Like, and most of them will like, you know, raise their hands. Like, if you can sleep on an airplane, you can sleep anywhere, right? You can, you can sleep, and, and, you know, we evolved to sleep in camps, right, where there's fires and there's hyenas in the distance and people running around and, you know, all kinds of crazy stuff happening. It's so much a matter of your, of what you decide bothers you rather than what actually bothers you. But, which is not to say that things don't bother us, but, but I think we need to be a little less judgmental about sleep and be more helpful rather than make people stressed about sleep.

Yeah. In your book exercise, I think one of the main things I took is more compassion towards myself in many regards, including sleep and exercise itself. But, uh, would you say, and I'm sorry if I'm again simplifying things, um, would you say that 10 hours plus is damaging and 6 hours minus is not?

I don't know. I mean, nobody knows. I mean, it depends on who you are. I mean, look, there's, if you, if you graph, if you take a graph, you get a large population, right? And you get data and good quality data because if I ask you how much sleep you got last night, you probably don't know. Actually, you may guess, but you're, you're, you're going to be inaccurate, right? So, but if you get data where you actually measure how much people sleep on the x-axis, and then you measure health outcome on the y-axis, like heart attacks or just how long they live or, you know, something like that, it's a U-shaped curve, right? And for most populations, the bottom of that curve is about 7 hours, right? So, people who sleep 7 hours tend to do better than people who sleep 8 hours or 6 hours, right? But it's, it's that's a single line and there's a lot of variation around that curve. So, where you fall on that curve and where I fall on that curve might not be exactly the same.

Yeah.

Um, and, um, and it depends on your age, your sex, your, you know, all kinds of factors, right? Uh, so, we need to be a little bit careful about it. Um, uh, and not, again, oversimplify. But I think most people know when they've got enough sleep. You feel, you feel crappy if you've not gotten enough sleep, and you feel good if you've gotten enough. And we all know the feeling of oversleeping. You don't feel so good, right? So, most of us, I think, actually have a pretty reasonable sense. And trying to be more precise than that is probably silly because you can't run the experiment on yourself and then find out later, you know, what your optimal is for your lifespan because by then you'll be dead. So, um, you know, just try to get enough sleep and don't, you know, don't go too crazy about it. The other thing, of course, is some of these, these, these curves can be contaminated by, by illness. So, for example, if I'm really sick or depressed, guess what? I'm going to sleep more. That's not because it's optimal for me. It's because I'm sick. So, so it's, you know, it's very,

It's complicated.

Yeah. H you mentioned the cortisol. I wanted to dive into more of those hormones and the way they shape us in regards of this mismatch. How about dopamine and all these other things that go through our brain and body?

Well, dopamine is a neurotransmitter, not a hormone. Sorry to be a professor here, but, um, look, I mean, our bodies are filled with various kinds of signaling molecules, hormones, neurotransmitters, etc., that regulate all kinds of things. Let's talk about cortisol before we get to dopamine because cortisol is pretty important, right? So, cortisol, uh, is, is a stress hormone. Now, and people often get this wrong. Cortisol isn't higher levels of cortisol don't cause you to be more stressed. More stress causes your cortisol levels to go up. So, if, uh, you know, suddenly a, you know, somebody screamed fire, or, you know, there was a, you know, a bomb went off, or, you know, around here, my cortisol levels would suddenly go up. And that cortisol is an arousal hormone that'll help me, um, uh, deal with the, with the crisis. The problem with cortisol is that it's, it's adaptive for short term, right? Cortisol. So, if I go for a run, right, my cortisol levels will go up, tell me get energy, right? So I can deal with my run. But then the problem is that you know, so that's good. But, but we don't, what, what's problematic is when cortisol levels are chronically high because then it can have pernicious effects. So, one of the things that cortisol does is that cortisol, because it's, it's a hormone that's out there to give you more energy to run away from the lion or whatever it is, it's going to, there's only so much energy your body has. So, cortisol turns off other things. So, one of the things it does is it turns off your, your, your immune system or it turns down your. So, when your cortisol levels are high, when you're stressed, you're more likely to get a cold because, or get in sick because you're going to turn down your immune system. Uh, cortisol also makes you hungry. So, people who are stressed, guess what? They eat more. They have, you know, in the middle of the night, they go to the refrigerator and, and eat whatever, right? Cortisol also causes you to store fat in temporary deposits in your belly. Belly fat, abdominal fat. That fat is the fat that we care about the most because it's the most damaging. That's the fat that causes inflammation. So, chronically high levels of cortisol caused by stress are, are, are terrible, right? And they, they cause, so people who are suffering from racism, from discrimination, from famine, from whatever, have chronically elevated cortisol levels, and it, and it has serious long-term negative consequences on their health.

Okay. Can I, um, before we go to dopamine and the other things, I myself come from a war-torn place, right?

Yes, I was thinking of that.

Yeah. And, um, let's say cortisol levels are, are high all across the board in our place, in my place. Um, what is your suggestion for people who, it's like, you know, the world is just making you be more stressed and have higher levels of cortisone? Is it something controllable still in these environments?

I mean, yes and no. I mean, to some extent, we can, we can try to tune up, learn strategies to, to not let, you know, politicians who get us upset and the circumstances around us elevate our cortisol levels. But sometimes we can't control them. If you're, if you're in a, in a, in a, if you're in, in the, in the, you know, if you're subject to famine, as a lot of people are in your part of the world, and constant stress, you can't just, you know, meditate your way out of it. Uh, so, uh, so these are real physiological consequences of, of, of, uh, so, I mean, there's no simple solution, and this, you know, it's a lot of these are environmental solutions that are outside people's control. Um, uh, u, but some of this, some, but to some extent, people can cope. Some people cope better than others.

Yeah. This is why I'm asking. It's very, um, uh,

You can see it very clearly. Some people take it better than others. The, the stress of our lives.

Yes. But sometimes there's nothing you can do about it either. If I'm in a, if I don't have enough food to feed myself and my family, do you think I can just meditate my way out of that? Of course.

No, no, no. But, but there is, in the same family, I see it all the time. Some people are reacting differently than others.

Yes. Yes.

Yeah.

So, yeah, this is a complicated situation, and cortisol is just one of those hormones. If you can go over to, to dopamine and serotonin.

All right. Well, so dopamine is a very complicated molecule. Um, is a, is a, I mean, plays many, it's a neurotransmitter in the brain, and it plays many, many functions, but one of them is, it's a kind of a reward molecule. It tells us to do something again, or tells us that you ought to do it, right? And, uh, so, like, for example, you know, in the morning, when I go for a run, I very rarely want to run. I mean, I mean, it's like, it's no fun, right? Um, however, um, after my run, um, I feel really good about it, right? I feel, I usually, you know, it takes me, you know, a kilometer or two, and I'm feeling better about my run, and I enjoy it, and I have a good time, and I come back, and I'm really glad I did it, even though I rarely wanted to leave the door in the first place. And, and then, and then my, um, but what that, one of the things that that run does, like any other, um, thing that you know, behavior that we're selected for, is that that run increases dopamine levels. It also increases receptors for dopamine, so that now my body wants another run, wants me to stay active. So, people

who are very active, um, become sort of addicted, slightly, to physical activity because they, um, their bodies, um, um, need that. And if I, you don't want to be around me if I haven't exercised for a few days. I'm, I'm, I'm grumpy and grouchy and irritable and, and unpleasant. It's because my dopamine receptors are screaming for more. So, so it's a reward mechanism. Dopamine also goes up for sex, or it goes up for eating good food, or gambling can cause, you know, dopamine, uh, whatever. So, it's complicated, but here's the thing. So, it's one of the reasons why once people, you know, people are physically active, it's a reward mechanism that keeps us being more physically active. It can also work against us. It can also keep us, get us eating more sugar because you can get addicted to sugar and you, we need that dopamine craving from your sugar.

But here's the thing. When, when you're overweight or obese, actually, really, you're more obese, especially again, visceral belly fat, you can actually cause, uh, insensitivity, uh, to the receptors of dopamine. So, if I go for a run and I, I get, I get a dopamine hit from my run, but somebody who's unfit and, and struggling with their weight goes for the same run, may not get the same reward. And yet we tell people, oh, you're going to feel great after your run. It's going to be all good for you, etc. It takes actually, if you have dopamine insensitivity, it can take you weeks to get to the level where you're actually going to get a reward. So, we need to be honest to people about how the system works, right? Oh, we often say that running, you know, exercise is a magic bullet. It's going to instantly make you feel better. It will eventually make you feel better, but the first few weeks, um, if you, if you're inactive and you're trying to get active, it's going to take you time to get there because your, your dopamine system is not going to be the same as the person who's fit and healthy, their dopamine system.

>> Yeah. So, is it correct that it's, I don't know if completely, but is it malleable, the the things that you can get the dopamine from? You can, uh,

>> Yeah, sure. It's, it's very, it's very envir, yeah. I mean, it changes. We have, we have some control over it. Um, uh, not complete control over it, but we have some control over it and it's again, it's environmental and you can change your environment and that's important. Again, it's all a gene-environment interaction that's matter. But if I hear Professor Liberman saying that I need to go for runs or go for walks, I can alter my brain to get dopamine from it.

>> Yes, but not, not instantly. It's not going to happen overnight. It can, it's going to be hard work and if you're unfit, it's going to be harder work than you might think.

>> Yeah.

>> But we need to give people that information so that they don't get discouraged, right? They think, "Oh, I went for my, I climbed, I went to the gym, as I, you know, I was told to by my doctor and I don't feel any better. Like, what's, what's all this nonsense about it being a, a magic bullet, right? I mean, it takes time. It takes, but eventually you'll get there, but it takes absolute time. And, you know, sometimes I hear the term, you know, people are exercise addicted and, you know, people wonder like, you know, it's not really, I think that's a really unfair term. Um, um, because we're assuming that if you don't exercise, that's the normal condition.

>> Yeah.

>> I think being not, not now, not having no reward system for exercise is to me abnormal.

>> Yeah. Can you elaborate more on this, uh, fairness? Because, yeah, in your book again, you said something about, uh, the in the beginning of going to exercise, going to lose fat, it's the, it's going to be harder because you are, you don't feel good about it, even.

>> Yeah, but it's also, it's harder for all kinds of reasons. Yeah.

>> I mean, you're, you're not going to be well adapted. It's going to, you know, you'll look, I'll give you an example. My mother, when she was, uh, in her 30s, when I was a kid, um, she, uh, decided to become more physically active. She was very unfit and, um, she decided to go running. She decided to run because it's a complicated story, but, uh, the, she was a professor at the University of Connecticut and they built this fancy gym, um, and they wouldn't let women use the gym and she didn't like that. So, she decided to become a runner to liberate the gym, but she could run only a quarter of a mile at first. Um, and it was hard and she actually hurt herself. I remember her coming home. She like tore her hamstring or something. It took her a long time to get up to where she could like run a mile. But over time she became, and she didn't like it, but she was doing it not because she liked it, because she was doing it because she was she was trying to make the gym available to women as well as to men. But eventually she became addicted, um, and she became a lifelong runner and she, unfortunately, she died recently, but she ran five miles a day for, I don't know, 40, 50 years, um, kept her very healthy, um, um, but that took time, didn't happen overnight. Right.

>> Yeah. So, and that's true for just about everybody, right? That's her experience is not unusual. Uh, so it takes time. You have to be patient and we need to be patient with other people and not give them false expectations.

>> Yeah. This is an amazing message. And if you can elaborate even more about fat, exactly specifically, because burning fat and exercise seem to be, uh, some misperceptions about the combination of the things.

>> Oh, there's a lot of controversy. Oh my god. I mean, let's first of all, if you have a lot of fat, just going for a walk or a run is just harder than if you don't because it's like, it's like putting weights on your body, right? It's extra work. So, somebody who, who's obese, who walks a kilometer is spending, I don't know, 20, 30, 40% more energy than somebody who's not. Um, so, and that's extra hard, right? Um, it's also more loading on your joints, etc. So, that can be tough. But, um, but there are other effects of obesity. Um, and that, that obesity causes, um, uh, insensitivity to various hormones. So, because obesity causes inflammation, right? Inflammation is when your immune system is kind of on, kind of constantly active all the time, right? And it attacks things all over your body. It's called chronic systemic inflammation. And so obesity has all kinds of negative effects and one of them, we just mentioned. It affects your dopamine sensitivity. It affects your insulin sensitivity. So, you're more likely to get diabetes. It can affect sensitivity to another hormone called leptin, which is which affects your, your body, um, um, how your body regulates, um, your, your metabolism and body fat levels.

>> It has all kinds of effects, all kinds of effects. Um, and, um, so, uh, so obesity is a kind of a vicious circle because once you're obese, then it, it kind of, it, uh, has negative effects on many, many, many regulatory systems in your body that, that, that are affected. But that's the bad news. The good news is that you can. And there's a big debate about obesity and exercise. So, so one statement you hear all the time now is that exercise isn't very good for helping you lose weight. Um, and so, it's, this is complicated. One of the reasons for that that people say that is that most of the time when people are obese and overweight, exercise is hard. And so when they do experiments where they ask them to do, people just do just 150 minutes a week, right? That's 21 minutes of brisk walking a day. Many people in those experiments failed to do it. So adherence to the prescription is very, very low. So if you look at study after study after study, the, you know, that looks at the effects of exercise on weight, etc. A large percentage of people in those studies don't even manage to do the very minimum amount of exercise. And it's not because there's anything, you know, they're bad people. It's because it's hard.

>> Yeah.

>> Right. So, so, so,

>> Just to clarify, you're still talking about obese people. Is like the

>> Yes, I'm talking about obesity, right? So, um, so people have say, well, you know, obesity, it's not, exercise is not very good for, and so you need to make a distinction between what we call effectiveness and efficacy. In English, efficacy is how well something works in the ideal circumstance. Effectiveness is how well it works in the real world. And so physical activity has efficacy for weight loss, but it has a low effectiveness. But the other issue is dose. How much you have to do. Now, if you just walk 20 minutes a day, that's, yeah, maybe a mile a day, you know, one and a half kilometers, right? Um, that's about what, 50 to 80 calories a day, which is not a lot of calories, right? So, you're not going to lose a lot of weight. I mean, you just eat a, a few peanuts and you've got that energy back, right? So, to lose weight, you need to actually exercise a fair amount. And so exercise, it's true, is not all that effective for losing a lot of weight fast, but there are plenty of studies which show that 300 minutes a week, so 40 minutes a day of walking, people slowly and steadily and gradually can lose weight and, and more can be better. But you, um, but you can lose more weight by dieting. So, people sometimes say, "Oh, forget the exercise, just do the dieting." But that's a really bad way of thinking about it because for two reasons. First of all, there's not an either-or. You can do both. Secondly, the reason most diets fail is not because people can't lose weight dieting. It's because they gain the weight back after the diet. The vast majority, if you don't eat a lot, you will lose weight. But, but most people gain their weight back afterwards. And study after study after study shows that people who exercise during a diet will lose a little bit more weight than people who just, just diet. But more importantly, people who continue to exercise after the diet is over are much, much, much less likely to gain the weight back.

>> So, and we know why. And because not only is it the energy that you spend, but also it changes your insulin sensitivity. It changes your sensitive, another hormone called glucagon. I mean, it has all kinds of effects on on your, on your physiology. So, and the dose required to, to not gain weight is not the same as the dose required to lose weight.

>> Yeah.

>> So, so sometimes people ask, you know, which is more important, diet or exercise? And I always answer the same way, which is a stupid question. It's a, it's a dreadful stupid question. I mean, since when is this a trade-off? You should, any diet should include diet plus exercise. And you, and if you're going to do it, you, if you're going to diet to lose weight, you need to think about what's going to happen after the diet, right? You need to, because you don't want to have done all that weight loss for no reason, right? You want to keep that weight off and that's going to, you're going to be much more effective, um, if you can include a component of exercise.

>> Yeah. And if I can make the the dist, distinguish, if I can distinguish between obese people and just regular people, like their BMI is not perfectly accurate, as the doctor said. What, why do you think those people are having trouble losing weight? Is it the same as you just said?

>> I mean, all of us have trouble losing weight. I mean, weight loss is hard. I mean, I mean, we are adapted not to be hungry, right? I mean, the reason people struggle to lose weight is that is is mostly because of hunger, right? I mean, there are all kinds of diets out there. There are low-fat diets and low-carb diets and low-calorie diets. All of them can work if you stick to them. The problem is that people have a hard time sticking to them or they do lose weight and then it comes back.

>> And the reason people have a hard time sticking to it is because they get hungry. Right? If I didn't eat enough, um, if I'm in negative energy balance, what a diet is, right? If I'm taking in less energy than I'm using, I'm going to be hungry. Right? That's what all creatures get hungry if that happens, right? And hunger is extremely hard to overcome. And, and it takes serious willpower to overcome hunger. And, um, and so, uh, there's no magic bullet. There's no simple formula.

>> Yeah.

>> Um, and people have to figure out how to cope with their hunger, uh, in order to diet. And, and that's, and, and, and one of the reasons that physical activity helps is that physical activity actually helps you with your hunger.

>> Yeah.

>> Changes your metabolism.

>> And now these days we have OAMIC and other drugs like that which just cancels your hunger.

>> Exactly. And that's why they're so effective. And, and, you know, they're the closest thing we have to a true magic bullet. But remember, Ompic, there are some problems with GLP1s, these drugs, which do, I mean, they have all kinds of wonderful benefits. I'm not anti-GLP1, but first of all, they don't prevent you from getting overweight or obese in the first place. So, people take them after they get, isn't it? It's better not to have to take them in the first place. Secondly, if you're taking them, you, it seems so far, you have to keep taking them for the rest of your life because once you stop taking them, your hunger goes straight back and you, and people tend to regain the the weight. Third, when people do that, they tend to often lose not just, uh, fat, but they also lose muscle mass. And that can be have really serious repercussions because as you get older, especially, you need to maintain that muscle in order to stay, to stay, to prevent what's called sarcopenia or age-related muscle loss, which is a major cause of disability in older individuals. And fourth, of course, it's expensive. And fifth, they can often have some side effects, right? All drugs have side effects and GLOP1s are no exception. Um, and so, so GLP1, be, GLP-1 drugs have been really helping a lot of people, but, but, um, but, you know, they're not, they're not the complete total perfect solution that some people like to think. Uh, I heard a doctor online said that, um, uh, will you can save your willpower for some things that better improve humanity instead of your hunger. So if it, just helps you with this willpower, it makes everything easy. So, uh, I, I, you said that the willpower is one of the main components in overcoming anger.

>> Yeah. I mean, I don't, I don't think I don't think you can just say willpower. I mean, people also say really bullshitty things about willpower. I mean, as if having enough willpower is just something you can summon up, right? When I'm really hungry, I, I'm, I'm hopeless, right? If I get really hungry, you don't want to be around me. I get hangry, right?

>> Um, it's not because I don't have willpower. I have a lot of willpower. I'm able to do all kinds of crazy things, but I'm not very good at dealing with my hunger. Is that, is that, is that a defect of mine? So having, I know which doctor you're talking about, but, but telling somebody, telling us that all you really need to do is conquer weight is willpower is, I think insulting. It's like telling a drug addict, all they need to do is just say no to the drug. We are adapted to get hungry and to eat food when we're hungry. And having and expecting people just to overcome it with willpower is, I think, um, is not going to work for most people.

>> Yeah. And this is why

>> Only a doctor who's divorced from from reality could say something like that.

>> Oh, yeah. I just say that Ompic perhaps gives you the

>> Well, Ompic doesn't give you willpower. It just, it turns off your hunger. Ompic doesn't affect your willpower. Ompic turns off your hunger.

>> So it's not affecting your willpower.

>> You don't need your willpower.

>> No. Exactly. So that's why it works.

>> Yeah. This, this is what I'm saying. Yeah. Okay. So this is just amazing. Thank you so much for all the information. It's incredible. Uh, in, in this case, I just, the, the thing that, most people are failing with their diet in losing fat, is it fair to say that in what you're saying, I'm hearing that habits make most of it is because

>> Well, it's habits. It's, it's lifestyle. It's environment. It's what you have available to you. I mean, if you're like, you know, in many parts of of America, right, there, it's hard to find inexpensive healthy food, right? That the, the really bad for you fattening food is cheaper. And if you're on a budget and you're stressed and you, so your cortisol levels already high, right? And you, and you have kids and you have, you're commuting long distances and, and all kinds of bad things are happening in the world and whatever, you know, you're going to be more likely to eat the food that's out there that's going to, um, going to then contribute to the fact that you're more likely to become obese.

>> Yeah.

>> Um, people can't just modify their environment at their own will, right? That's not easy, right? Uh, being thin and physically active is now a privilege of of the wealthy and the, and others. I mean, I, I'm very lucky. I have a nice job. I have lots of time. I get to go running in the morning. Um, because I don't have to drive to work long distances. I, I am, um, you know, I can get, I can, uh, you know, you go to marathons, right? Like big city marathons around the world. Guess who's running them? They're wealthy people, right? Um, um, um, you know, Ironmen, the triathlons. These are millionaires who are able to do that. You, you think flying to Hawaii with your $30,000 bike is like for the average person? Of course it isn't. Right. So, so physical activity and being thin is actually now a privilege of, of, of those who are better off in our society.

>> Wow. This is fascinating and I never thought about it this way. Um, I wanted to go into your, uh, specific, uh, uh, story or approach to this, uh, field. What made you go into from evolutionary science to, uh, starting to, uh, think about exercise and physical activity?

>> Well, it's a long story. Um, I'm not sure it's that interesting, but, you know, I started off as a, um, you know, I've always been interested in human evolution. And when I was a student, I got really excited by studying how and why humans evolved. And I was really, I was a skull guy. So I worked a lot on, on the evolution of the human head. Um, and, um, but I also, uh, I've always liked being physically active and partly because of my mother. Um, and I was never a serious athlete, but I just like to hike and run and things like that. And, um, and in the 19, uh, you know, you know, at some point I started getting interested in, in, in how we use our heads to stay, how we keep our heads still when we're running. So, if you watch somebody with a ponytail running, right, you watch them running, that ponytail goes up and down and side to side. It's like an accelerometer on the head. So the head is staying pretty stable, but there's all kinds of forces acting on the head that that ponytail is essentially measuring. And so I got kind of curious because I was working on, on the head. I wrote a big long book called The Evolution of the Human Head that nobody's ever read. Um, big academic book, but I had a chapter about the head and locomotion. And so I started wondering about head stabilization. And I worked and I got interested with a colleague of mine, a guy named Dennis Bramble, a good friend of mine who's at the University of Utah. And because he was interested in some of the same topics and we, we came up with this, you know, Bramble had been very interested in, in, in running because a student of his named David Carrier had been working, had been interested in sweating and running and long story, but anyway, long story short, I got infected with this idea and we, we started studying a a feature on the on the back of the skull called the the nucle, it's, it's, it's a, it's a ligament. It's really, it's, it's actually a tendon, but it's called a ligament called the nucal ligament, which is turns out to play a really important role in head stabilization. And chimpanzees don't have it, but we do. And other animals that run have it. And we discovered that this traces of this ligament first appear in the genus Homo starting around 2 million years ago. You could see it on fossil skulls.

>> And that was like a Eureka moment. And so we started working on this hypothesis that there was selection in the genus Homo for us to run long distances in order to hunt. And we ended up publishing a paper that was in the journal Nature, was on the cover, um, entitled Born to Run in 2004. And so we started studying and we, and for that paper, we spent years, Bramble and I writing that paper. We probably spent about three years writing that paper, putting together all the evidence that humans evolved to run long distances, all the anatomical features, etc., and, and making the argument that it was in the genus Homo. Um, and when the paper got published, it, it kind of went viral. I mean, it, it went all over the world. There were like every major newspaper covered it. It was pretty, pretty interesting experience. And, and, um, I, of course, and of course, people in my field, the paleoanthropologists didn't like it because they, far as they were concerned, human evolution is all about walking and this running is kind of stupid, what these people arguing this. But everybody else, the exercise physiology world, the exercise science world, you know, runners, I mean, I got letters from people all over the world about this paper, um, because they were excited by it because we basically made the argument that, you know, running long distances isn't this weird thing that just athletes do. It's something that we're evolved to do. It's part of who we are. And it helped, it's not the deterministic thing, but it helped make us who we are. And, um, and of course, I, I immediately started getting interested in, in, of course, running is a form of physical activity. It's for, it's the most natural form of vigorous physical activity. So walking is moderate physical activity, but running is vigorous. And if we evolved to run, then I started thinking about why is running so healthy. And, um, I started getting more and more interested in this field called evolutionary medicine. And, you know, when I'm teaching my classes, you know, I teach a big human evolution class at Harvard. When I teach the students about, you know, different species, you know, Australas, and Australus, that, or these different species of early Homo, I mean, you know, they learn it because they're good students, but they're not all that interested because what, what is it to them, right? But when I start talking about the evolution of running or, and how it's relevant to health, or walking, it's relevant to health, they start paying attention, right? Because they care about it, right? Matters to them. And I realized

>> And I, you know, I was having a midlife crisis and so I started writing a book called The Story of the Human Body. And, um, um, I'm not making this up, but the, the, the file on my computer, the original title of the book, which I was never planning to use for the title of the book, was why should anybody give a about human evolution? Because after all, you know, why should most people care? And the answer is mismatch, right? And, you know, what are we adapted for? And one of the things we're adapted for, it's not the only thing, is to be physically active. And so I got more and more interested in how evolution is relevant to health and how, how it can help people use their lives, make them better, um, than just what happened on its own in human evolution. And, and that's very empowering. Even though it's led to all kinds of debates and, you know, whatever, ultimately, you know, if you can make the world a little bit of a better place, um, uh, you should, right? And it, and, you know, if we can, if I can help people understand physical activity and use evolutionary principles and, and diet to help them to, to be healthier. I mean, uh, uh, that's rewarding. Uh, so it's kind of given gotten me excited about doing all kinds of things that I never would have otherwise done and, um, and so that's keeps me going.

>> Yeah. Is it fair to say that it was like a dialogue, uh, between you and the people reading your research and

>> Well, of course. I mean, you know, academics, I mean, there, one of the problems with some academics is that they're, they're doing research that only like 12 other people in the world really care about, right? And, you know, sometimes that's actually can turn out to be very important, but often it's not. And, um, you know, I mean, I didn't, I mean, I was writing papers about chins and brow ridges and, you know, things like that. And, you know, okay, humans have chins and Neanderthals don't have chins, but ultimately, who cares, right? But, but writing about how we evolved to run and why that can help you avoid heart disease, I think most people care, right? Sounds like, and the evolutionary part is some of your passion towards the field. And I imagine that going to Kenya and all these other places looking at the, um, researching the Paleolithic world in quote unquote was exciting for you personally. Am I correct?

>> Oh, yeah, absolutely. I mean, I, I, I've been very, I've been extremely fortunate to travel a lot in my career and, and, and, you know, I still love fossils, you know, but I also care about people, right? And I don't see a distinction between the two.

>> We are who we are because of what those ancestors of ours were like. And it's all connected. And so I see, I see the relationship between the fossil record and, and the people who are alive today as as part of a continuum.

>> Yeah. And do you, uh, the, the specific, uh, thing about running that you mentioned, the, the that we adapted to run long miles. What does it say to you about, uh, about our nature? H, what is the consequences of this discovery, do you think?

>> Oh gosh. Well, I mean, that's that's complicated. Look, when you walk out the door, if I leave, if I leave this room, right, most of the people I will see will be walking. They won't be running. So, let's be first be clear. It's not all about running. It's about moving, right? And, and so we walk and we run. And walking is the most fundamental form of moderate physical activity, but running is the most fundamental form of vigorous physical activity. And, and, and vigorous physical activity is just part of the mix, right? If you want to be really healthy, it's good to walk. I mean, that's the most important thing. Everybody should just walk a lot. But if you can also occasionally get your heart rate up, that's also beneficial. And before swimming pools and exercise machines, you know, the ellipticals in a gym or whatever, running is how people got their heart rate up, right? It's. And so, um, and it's also how we got dinner. Um, and so we have adaptations from our heads to our toes to not just walk, but also to run. And they're not the same thing. Walking and running are, are actually biomechanically very different. So running is, running is just not fast walking. But also, uh, running does things for your body that that walking alone cannot do. So, um, uh, it's incredibly beneficial for your cardiovascular system, for your heart, for your, you know, for, for your, for your brain, for Alzheimer's, etc. Uh, it's, it's part of who we are and you don't need to, you know, run marathons in order to get the benefits of running. Um, and not everybody needs to run. There are other ways to get vigorous physical activity. You can go to the gym and use various machines if you're have joint problems or you can swim. I mean, people, until recently, nobody swam laps in pools because pools didn't exist. And if you were in Africa for most of human evolution and you want to go swimming, you have to worry about crocodiles, which is not a good thing. So, so, um, so, you know, um, um, so, you know, running is just part of who we are and, and, and we can learn a lot about, about the benefits of physical activity, uh, by studying running.

>> What about just, uh, learning more about who we are in this, in the consequence of this discovery? What, what does it say about the human nature? I, I think

>> I don't, I mean, you know, I mean, look, it's complicated. People, all kids love to run, right? You, you want to torture a kid, prevent a child from running, right?

>> Running is part of play. And as we get older, a lot of us stop playing, right? Um, and why do we play when we're young? Well, playing when you're young is an adaptation to help us learn, develop capacities, develop skills, you, um, it helps us learn to be better people. So we don't, if you, the other team scores a goal, you don't punch them, right? Um, play has all kinds of benefits, but one of them is to, is to help us become physically fit, adult adults who can then do things. And of course, for millions of years, that play as a kids helped adults be able to run so they could hunt because hunting, what we call persistence hunting, was very important for evolutionary history. Now we live in a world where we don't have to run anymore. Children still need to play, but adults no longer need to run. And so now we invent reasons for us to run. Like, you know, I, I sign up for various, you know, races like, you know, I just did a half marathon not too long ago, right? And, um, um, but I didn't have to do that. I did it because I wanted to do it, right? Um, but I got a lot of benefit from doing it, right? It was great for my cardiovascular system. It was great for my immune system. Is great for all kinds of things in my body, right? Um, and, and, you know, I can tell you, um, uh, standing at the finish line watching people finish after they, you know, a lot of them were people who hadn't run a half marathon before in their life. Um, uh, it was called the Great North Run. It's the largest half marathon in the world. And I can tell you, it was a beautiful experience watching all these people who, who had never run a distance like that, cross the finish line and see just how happy they were. Um, they were elated. They were, they were high, right? And they were, a lot of them ran not just, um, for themselves, but they ran for charity, right? They were raising money for really good causes. And I think that's also important because we ran in the past in order to help each other to get dinner, to feed our families, and to feed other people in our, in our group. And so people today are using that same instinct to help each other. They're raising money for cancer and Alzheimer's and all kinds of other wonderful causes. Um, I think it's part of the same phenomenon. So we ran not only to help ourselves but to help each other. And I think that's still the case. And it's, and, you know, you don't have to run to do this, but there's no question that, um, it is, uh, it has real benefit and real power and, um, you know, really does make the world a better place.

>> Yeah. You mentioned the fact about the rich got the time to do it. Uh, I think a lot about the fact that if I'm not mistaken, Obama, during his administration, was getting up every morning to run for an hour at least, uh, which makes me humble when I don't want to go to run. It's like he ran the world when he ran.

>> Yeah, I mean, and, and the number one reason people give for not exercising, whether it's running or walking or whatever it is, it is the people say they don't have the time.

>> Yeah.

>> It's the number one reason people give and, um, and I just don't believe it. Uh, as you say, if Obama had time to do it, or to be honest, let's be, let's be equal. George Bush also ran. I mean, a lot of presidents, Jimmy Carter ran and lots of presidents ran.

>> Trump doesn't run.

>> I don't think Trump runs. No. But anyway, um, um, um, there's no question that, um, uh, you know, we all have trade-offs in time, but one thing that running or other kinds of physical activity does is it actually helps your mood, it helps your energy levels, it helps you sleep better, it helps you do all kinds of things. And, and you get the time back in in increased concentration and in, and in all kinds of, and, you know, in, in better mood and better sleep. And so it's rarely actually, uh, um, uh, you know, look, you don't, I mean, you don't have to run an hour a day in order to get the benefits of running, but, you know, even like 20 minutes of something, you know, can have huge effects on your day. And people, I always ask, you know, when students tell me they don't have time, I ask them how much time they spend on social media. And they, then they usually don't answer the question because they know full well that they spend hours a day, you know, on their Instagram or whatever the hell they're, you know, on, and they could have spent some of that time

>> Um, exercising.

>> Well, this time is just one of the, uh, components of the damages, uh, from social media. Can you just give us a little bit more because we, we touched it. My, my instinct is it's, you know, it has some benefits, but the costs are huge and, and we, we're still figuring them out and, and, and, and they're, they're seriously concerning.

>> Yeah. Okay. So, I, I wanted to ask, um, what you talk a lot about doing good in the world and making it, uh, a better place, even. Um, what do you think or what can you say that it's your mission, uh, when you, in spreading this, uh, knowledge because you do touch millions of people with with these books and lectures and everything?

>> Yeah. I'm just trying to, you know, help people. Look, here's how I would think about it, right? We, I think it's useful to have a philosophy, right? I think everybody needs to have some kind of philosophy. You don't want to die thinking, gosh, I misspent my life, right? I didn't use my life. You mean, we have one chance, right? You have one chance in this incredible gift that we've been given to, to live a good life and to, and to, and to, and to make the most out of it. And you don't want to be on your deathbed thinking, you know, I, what did I do? What, what did I waste my life on? Right? And you, and at the same token, you also got, you have one body. I mean, I don't, I don't have another body. I have the one I was born with and I didn't get to choose it. It was given to me or determined to me by by accidents of birth and, and whatever. And I think we need to have a philosophy of how we use our bodies, you know, to use them as best as possible. And, uh, and part of that involves, uh, knowing how to use our bodies and part of that involves knowing an evolutionary perspective because as the expression goes, nothing in biology makes sense except in the light of evolution. We didn't, we didn't, that my my body wasn't engineered or designed. It, it, I, I inherited it from my ancestors who inherited it from their ancestors and gone back and back and back and back and back in time. And so understanding that evolutionary history helps us, I think, use our bodies better. And

>> So my job is to try to help marshall the evol evidence from evolution, uh, to, um, and integrate it with other kinds of science, you know, medical science and, and whatever, to try to help people, uh, make better uses of their bodies so that they can get the most out of that's my, that's what, that's, that's my, that's what motivates me. And you would wish that more people would be interested in the evol evolutionary components of the owners.

>> Well, I think it'll help them. I mean, I think especially if they're in medical science, right? You know, there's so many doctors who don't know. Look, doctors are can do wonderful things, but they're also some of the most ignorant people I know because they, they, they think that they know everything and they don't, and they don't know why things work. And they also are taught one set of, uh, skills, but they sometimes at the expense of some other skills. You know, look, not criticize some. I obviously work with a lot of doctors. So many of my best friends on the planet are doctors, and they, most of them will actually agree with me. It's a, it's a medicine is has has a capacity to do great good and also do great harm, but it's also not just medical medicine. We overmedicalize a lot of things like medicalizing exercise has failed, right? A doctor telling you to exercise doesn't get you to exercise. Doctors are, you know, the medical world is is mostly geared towards helping people once they get sick, not preventing people from getting sick in the first place. And the best disease is the disease that never happened. So, for example, according to the, the Center for Disease Control in the United States, CDC, 70% of the medical conditions that Americans suffer from are preventable, right? And that's probably an underestimate. So why don't we do more to prevent those diseases, right? Many cancers are preventable. I'd much rather not have the cancer than than have to deal with it in the first place. And if I do get cancer, I will go see a doctor and I will, we will do whatever we can. But the best thing to do is not get that cancer in the first place. And

>> How do you explain that it's not the way it's happening?

>> Why? Because it's not, why don't we spend enough energy on prevention?

>> Yeah.

>> Because a bird in the hand is, is actually always worth two in the bush, right? So we, we, we, we, we engage in hyperbolic discounting. Yeah. We, we, we, we, we have that candy bar today and tomorrow I, I'll, I'll not have the candy bar. We take the elevator today and tomorrow I'll take the stairs. We, we, we, we delay all kinds of things that we know are good for us. People who smoke, they know full well it's bad for them. I'll quit eventually, you know, or I, I'll just one cigarette now, or I could go on, right? And because it's the urgency. Prevention doesn't have the same urgency as treatment. So when you get sick, you have an urgent need to treat it. But when you're trying to prevent something, it's not urgent.

>> Yeah. My question is not about the the general public, but for the the medical industry.

>> But they're not paid to do it, right? Doctors aren't paid to prevent. I mean, how many, you know, like a heart doctor is not paid to treat your hypertension before you get sick.

>> That's somebody else's job, right? And we don't, but the problem is that nobody, it's really nobody's job. We have schools of public health. Public health is underfunded. Um, we, you know, it's, it's nobody takes care of this, right? So, so the end result is that lots of people get sick from diseases that they don't need to get, um, and then, and then we spend vast amounts of money and people die and suffer huge amounts because, um, from preventable diseases. Now, look, I'm not claiming that exercise and diet are magic bullets. You cannot

>> Guarantee that you will live to be 100 and never get sick, but you can reduce your chances. You can reduce your vulnerability to a wide range of diseases by by paying attention to how to live your life better. And one of the important tools is to use evolutionary theory. Although not in a simplistic way, right? So it's not like just emulate a hunter gatherer and just, you know, you know, follow the nonsense of the paleo diet or whatever. That's not, I mean, it's not all nonsense. It's just partly nonsense. I mean, Paleo diet says you should never have legumes.

>> Yeah. No lentils, no chickpeas, no, you know, I mean, what I mean, tell me, really, do you really think people who eat lentils and chickpeas are going to die young? I mean, that's just obvious silliness, right? But, but there's some other good messages from the paleo diet. I mean, it's another story, but, um, um, um, uh, so that evolutionary information, if used properly,

>> Done sensibly, paying attention to the complexity and test hypotheses, don't just make simplistic assumptions that can help us.

>> Like, like you said before, when you published the first, uh, uh, Born to Run paper, you got, uh, some pushback from the status quo, people who want to keep it that way, perhaps. And perhaps this, this is the, the way it always been with science.

>> It's not just science. It's just human nature.

>> Human nature.

>> Yeah. People always, um, um, look, it's my job as a scientist to be skeptical. When I pick up a paper, it's my job to say, "How is this wrong?" Right? So that's their job and they, and they need to, that's okay. Um, but sometimes it gets a little silly. Um, uh, I would have to, I have to say, by, by now, I would say, you know, it's more than, uh, 20 years since we published that paper, actually. Um, and, um, um, and, uh, and now I would say, actually, it's now become, it's, it's now become part of the status quo, but it took, you know,

>> We published dozens and dozens of papers, you know, trying to test various components of the hypothesis and slowly, slowly,

>> Um, it's, it's become accepted, but it took time, but that's okay. That's, that's the way science works.

>> Yeah. This is the right approach, I think. Okay. Before I ask the, the last question. Uh, just one more thing that I, I, I hate to leave behind. You've mentioned a couple of times about longevity, but the paralytic world, you said seven centuries is the

>> Seven decades.

>> Seven decades. Yeah, of course. Um, how about modern places like, you know, the studies about Japan and stuff like that?

>> Blue zones.

>> Blue zones.

>> Oh, I'm going to get in real serious trouble for this one. Look, I mean, Blue Zones is mostly marketing, right? Think about it, right? You got five little V places in the world. One in Costa Rica, some village in Sardinia, Loma Linda in California, where the Seventh Day Adventists I live, um, Okinawa, and some island in Greece, I think it is. Those just those five places, those five, that's it, are where there's a a high percentage of centenarians. So the idea is that if you live like them, you too are going to live to be 100 years old.

>> Yeah. Romantic idea.

>> So here's the, here's several problems. The first is, even in place, those places, that out of a 100,000 people, maybe, you know, uh, 40 live to be centenarians. So we're talking 0.04%. 04% of the population.

>> Oh, really?

>> Yeah. And I'm sorry, but those are, that's called a statistical outlier. You should not make your decision about how to live your life based on a statistical outlier. That's like deciding, well, you know, those people don't get hit by lightning, so that's how I'm going to live my life, right? That's not how it works, right? You, what you should care about is what the average person in those populations do. Guess. So, and Japan has the highest average longevity in the world. Guess, guess what country is

number two?

>> I have no idea.

>> It's Switzerland. I can tell you in Switzerland they don't eat anything like a blue zones diet. They eat tons of cheese and whatever, you know. I mean, you know, they eat lots of meat and they probably, you know, I I don't know exact Swiss diet, but but look, so so you're just as well off living like a Swiss person as you are like a Japanese person, right? So it's a very it's bad statistics to to to make your decisions based on outliers. you should go based on the mean.

Secondly, think about blue zones. If you somebody who's in a blue zone in in a in a some like this v village, I have never seen a study which compares what they eat and how they live their life with like three villages over where they probably have ex do they have different diets? Do they live their lives differently? I doubt it. Right. Um I've never seen the study because we know what the answer of that study would be.

>> So there's so so you you know it's just I don't know. Look, but that said, most of the stuff that the Blue Zones diet suggests is pretty sensible. You know, eat a lot of plants, don't, you know, get exercise, don't drink too much, don't smoke. Um, do you need centinarians to tell you that? I mean, so there's a lot of marketing because people are out there, everybody wants to live a long life. There's money to be made

>> and there are lots of people out there trying to figure out how to make money off of this and this is just another way. So, are is the basic evidence basic recommendations of the blue zones wrong? No, they're not.

>> But are they is it because these people in these villages live to be centinarians? No, that's just that's And furthermore, there was a paper that was just published

>> that showed that a large percentage of the people in the in the blue zones don't even have birth certificates

>> and that and that the evidence that's being used to claim that these people are centinarians is kind of suspect. Oh yeah. But but the thing I found I've heard about Okinawa and specifically from the book I think some of the listeners might know it. It's a eky guy which it says a lot about the way they live other than their diet. The the thing is that they have they have the this

>> but the blue zones diet includes stuff other than than diet.

>> Yeah. Not only the diet they they eat.

>> But again do you who doesn't already know that? I I think many people from where I come from the the big fantasy is retirement for example and Okinawa is like the the place that where they work till they die the till the last day where

>> well it's not the fact that they work till they die so they stay physically active until they die.

>> Yeah.

>> Right. I mean you I mean sure retirement can decrease people's life expectancy but it depends on how you retire.

>> Oh yeah. Yeah. Okay. So uh last question about your future uh what uh does your re research involves in the upcoming future?

>> Um well we're you know we have a lot to explore in terms of physical activity and diet and its effects on health. So we're looking at all kinds of um um um factors in my lab. We're looking at everything from, you know, from heads to toes, literally. Um but uh a lot of the work that we're doing is is uh focused on on on um on countries that are going through this physical activity transition and also this dietary transition

>> because you know um we have a current we don't see this but it's we have a current crisis that's building around the world because you know in America for example only 25% of Americans have normal weight. Yeah. 75% of Americans are either overweight or obese. The numbers are growing around the world and um and that all those pro that's causing a wide range of health problems, cancers and diabetes and heart disease and and so on uh arthritis uh we can barely cope with that. what's going to happen in places like your Rwanda or Kenya or I could you know all kinds of countries what as they go through this transition because they're getting these diseases increasingly but they have a high infectious disease burden on top of that and they have health care systems that are you know I mean we have a terrible health care system but we still have a pretty large health care system that how are they going to handle this right so we have a a current rapid explosion of chronic diseases causing by lifestyle happening around the world and and and and we can't wait just to simply treat those diseases uh because we're not going to be able to. We need to prevent those diseases. And so uh what my lab is really interested in is is from a global health perspective how to confront uh changes in lifestyle, diet and physical activity to to kind of see if what we can

>> do to alert people about this and help them understand it so that we can make better decisions.

>> You you mean per se making the these countries make changes in their lives?

>> Help them make changes so they understand what's going on, right? Because they need the data, they need the information. I mean, you know, again, a lot of the information we have about weight and health, for example, comes from Americans. So, you know, standard studies are you have overweight Americans, obese Americans, and they exercise.

>> Well, that's not what's happening in I'm just picking on Rwanda because we're working there at the moment. But yeah, that's not what's happening in Rwanda. And what's happening in Rwanda is that people are going the other direction. They're highly physically active and then they stop being physically active. And it's not like like a street with two directions and just going back and forth is you know becoming less active and you you know the the most of the research that we have is going is is about what happens in the wrong direction trying to help people who are already physically inactive already obese whatever become more active and what's really happening in those countries is the opposite. People are going from being very physically active and very thin and eating healthy diets to to the other direction. So we need to understand that transition better. Great. Okay. Thank you so much again for your time. H just one le thing last thing I usually ask the the people that come to to the show. What's the one thing you think people should take from uh this conversation if you had to choose?

You don't need me to tell you how to live your life better. you know, it's, you know, there's a wisdom in in some of the older ways. Um, you know, just a few just a few simple shifts to our lifestyle can have massive massive effects. Um, they're not magic bullets, but they can have massive effects. So, you know, and and I don't you don't even need me to tell you what they are.

>> Thank you so much, professor. It was a pleasure.

>> Pleasure. Thank you so much.