Dr Lieberman is the Chair of the Department of Human Evolutionary Biology at Harvard University. His research focuses on how the human body has evolved to be the way it is, he also explores how humans evolved to run long distances to scavenge and hunt. He is the author of the best-selling books, ‘The Story of the Human Body: Evolution, Health, and Disease’ and ‘Exercised: Why Something We Never Evolved to Do Is Healthy and Rewarding’.



In this conversation Dr Lieberman and Steven discuss topics, such as:


 Sitting isn’t actually the new smoking
 The unseen health benefits of running
 The best exercises for a healthy life
 Why you don’t need 8 hours of sleep a night
 Separating the health myths from reality
 How the world has become too comfortable
 How 74% of diseases can be prevented
 Ways to hack and boost productivity



You can purchase Dr Lieberman’s newest book, ‘Exercised: The Science of Physical Activity, Rest and Health’, here: https://bit.ly/44fKyog



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A lot of people exercise because they believe it will help them to lose fat.

Author and professor at Harvard University.

He has the answers on all of those things that most of us care about.

We evolved to be very physically active, working in the fields, hunting, gathering.

But now we live in a world where only 50% of Americans ever exercise, and the rest of the world is headed our way.

Cancer is depression, anxiety, you can attribute that to less physical activity.

In fact, women who get 150 minutes of physical activity a week have about 30 to 50% lower breast cancer risks.

The problem is that we spend 3% of our medical budget on prevention, and yet 75% of the time, the disease is a preventable disease.

It's a completely backward stupid system.

When you started writing this book about exercise, was there any instant changes that you implemented into your own life?

The more I study the importance of doing weights, especially as you age, the more I start kicking myself for being lazy about that when people retire they become less active They tend to lose muscle and then that starts off a vicious cycle.

So how does 1 go from having a negative opinion towards exercise to becoming an exerciser.

As an evolutionary biologist, there are multiple ways of doing that.

What are some of the biggest myths within exercise?

He's been to every corner of the world, visiting native tribes to understand how humans are supposed to live.

And now he has the answers on all of those things that most of us care about on sleep, nutrition, exercise, disease.

You know, on disease, he says that 74% of them can be prevented.

He tells me the story of a CEO that forces his employees to exercise and the impact that that's had on that company.

And he talks about how as humans, we've evolved to either use it or lose it.

So maybe, maybe retirement is a really bad idea for many of us.

1 of the most thought-provoking, pivotal conversations I've had on this show.

You're really going to take a lot from this 1.

And I suspect, after listening, you'll probably start running too.

For exercise, or from some of the decisions you've spent your life making.

Daniel, your work is so incredibly impressive, reaches such an incredible depth, charters new territory.

And it's been an unbelievable, clearly very passion driven career you had.

So my first question for you is why are you doing this?

I started off being obsessed by human evolution.

Ever since I was a kid, I was really interested in human evolution.

And I spent much of my early career working on skulls and heads and why they are the way they are.

And then I kind of got involved in public health and issues of health and disease kind of through the back door.

I sort of slowly shifted my research trajectory towards studying the evolution of running and then the evolution of physical activity and its relationship to health and disease.

And I've become part of a movement that's often known as evolutionary medicine, which is how to apply evolutionary theory and data to issues of health and disease.

Evolutionary medicine, I've never heard that term before, but I love it.

Where has your work on evolutionary medicine, let's call it, Where has that taken you?

Where has it taken you to learn, to research, to study?

You know, so much of what we think about in terms of health and disease comes from a tiny fragment of the world's population.

Almost entirely, like 90% of all the medical information comes from people from the United States, Canada, Europe, and Australia.

So in order to study how bodies really work and how our bodies evolve to be, you have to leave places like Boston where I live and go to places like Africa or Mexico or wherever to look at other populations and look at how those populations are transitioning to lifestyles like mine.

And so we've been working in Kenya for the last 15 years or so.

I've traveled to some other parts of the world as well, India, to kind of collect some data, but mostly in Africa.

After doing all of this work and after taking in all of this information, how has it shifted your perspective on running, exercise, more broadly?

Have there been any sort of significant cognitive perception changes?

Yeah, I actually had a, I mean it doesn't happen very often, but I had kind of an epiphany moment when I was working in Mexico.

We were collecting data on the Tarahumara, very also famous for their long distance running.

And there was this elderly guy, he's about 70 something years old, and he's famous for his distance running.

And I was asking him how he trained, and I had asked this question to a whole bunch of other people.

And the translator I was working with was always struggling to ask that question, because it turns out There's no word for training in that language.

So, she was trying to explain to this guy what my question was.

Even without a translator, I could figure out just from his tone of voice, he was like, why would anybody run if you didn't have to?

And I suddenly realized, yeah, of course, exercise is a very weird thing, right?

Well, if you're a farmer and you're working super hard every day in the fields without machines and whatever, or if you're a hunter-gatherer and you're walking, you know, 5 to 10 miles a day and digging and throwing, you know, doing all kinds of hard work and you're barely getting enough food, why on earth would you go for a needless 5 mile run in the morning?

The most viewed videos of yours and the most viewed moments in those videos Address 1 question.

I think you actually pointed out 1 there with the insight you got in Mexico the way we exercise going to gyms practicing is the natural or human but evidently it's it's a consequence of the privilege of our lives and the comfort we have of not having to seek out our dinner every day.

What are some of the other biggest myths within exercise that you've come across in writing this book?

So I think if you want to understand physical activity and exercise, you also have to understand inactivity.

And I think 1 of the biggest myths out there is that you need 8 hours of sleep a night and that sitting is when you're smoking.

That basically, if you think about those 2 different myths, why is it that we're constantly told to sleep more and to sit less?

Actually, it seems a little contradictory to me, right?

And it turns out that, let's take sitting first.

So, there are all these slogans like sitting is the new smoking and it's really bad for you and every time you sit in your chair you lose 2 hours of your life and whatever.

My dog sits, cows sit, chickens sit, every animal sits, and hunter-gatherers also sit.

In fact, some of my students actually put sensors on hunter-gatherers, and we're doing some research in farmers as well, but they sit just as much as Westerners.

So sitting, there's nothing special about today's life.

It's that we sit all day long and don't do anything when we're not sitting.

And furthermore, the big difference is not so much how much we sit, but how we sit.

So it turns out that people who, if you get up every once in a while, interrupted sitting is actually much more healthy than non-interrupted sitting for the same amount of time.

So in other words, 2 people might, In the West, people sit for an average of about 40 minutes at about, whereas hunter-gatherers, for example, or farmers in Africa where we work, get up every about 10, 15 minutes.

When you do that, you actually, it's like turning on the engine of your car, you know, drive it around the block.

You're turning on all kinds of cellular mechanisms, you lower blood sugar levels, all kinds of genes get activated, and it turns out that that is by far the most important way to sit.

So just get up every once in a while, just pee frequently, make a cup of tea, pet your dog, whatever.

Thinking when I'm on planes and I've got a long flight.

I always sit in the aisle, right, so I can get up a lot, always.

So this idea that you need 8 hours of sleep has been around for a long time.

It's been around basically since the Industrial Revolution.

But if you actually, so colleagues in my field, so in evolutionary medicine, have put sensors on people who don't have all the things that we're told have destroyed sleep.

We're told that TV and lights and our phones and all these things are preventing us from sleeping.

So when you put sensors on people who don't have any electricity, they don't have TVs and they don't have phones and they don't have any of these gadgetry, right?

It turns out, they sleep like 6 to 7 hours a night.

So this idea that natural human beings sleep 8 hours a night is just nonsense.

And furthermore, when you start looking at the data, 7 hours, if you actually look at, if you graph sort of how many hours a night you sleep on the x-axis, and sort of some outcome like cardiovascular disease, or just how likely you are to die.

So people who don't get much sleep are in trouble.

But the bottom of that curve is pretty much always about 7 hours.

So people actually do better if they sleep 7 hours rather than 8 hours.

And yet we're told that if you don't sleep 8 hours, there's something wrong, right?

I mean, there's also some complexity to this too, because of course people who are ill might be sleeping more.

And so there's some biases that creep into how you analyze the data.

But basically it turns out that 7 is, for most people, optimal.

Teenagers sleep more, older people sleep less, it's complicated.

1 of the things that's popular in culture as well is this idea of doing 10, 000 steps a day.

That started because of a Japanese pedometer.

Right before the Olympics were in Tokyo in the 60s, they had invented the pedometer.

And they were sitting in a boardroom and they were discussing what to call the pedometer.

And just out of the blue, they picked 10, 000 steps because that's apparently an auspicious number.

Interestingly, it turns out it's pretty good.

If you look at steps per day and health outcomes, your average hunter-gatherer walks between 10 to 18, 000 steps, depends on male, female, et cetera.

And if you look at steps per day and outcomes, at around 7 to 8, 000 steps, the curve kind of bottoms out.

Doesn't seem to be a huge advantage to taking more than that per day in terms of large epidemiological studies.

So it turns out to be not that bad a goal, but it's not a perfect number like a lot of things right.

It's just a kind of a it's a reasonable It's a reasonable goal to shoot for

when you um when you started writing this this book about exercise and running and all these subject matters was there any instant changes or any real lasting changes that you implemented into your own life from everything you'd learned.

I think about that all the time with this podcast.

I'll have a guest on, I'll have these mini Eureka moments and then something will stick.

So I'm wondering, having studied all of these people all around the world and looked at their bodies and exercise and physical exertion.

What have you taken into your own life that has stuck?

I would say that I've become more serious about doing some strength training.

I've always loved walking and running and endurance kinds of activities, and I've always sort of hated doing weights.

The more I study the importance of resistance training and the more I study the importance of doing weights, especially as you age, the more I've started kicking myself for being lazy about that.

So now I try to do a good 2 strength workouts out of every week at least and take it more seriously Because especially as you age, loss of muscle mass can be really debilitating.

The technical term for that is sarcopenia.

Sarco is the Greek word for muscle, and penia is loss, or muscle loss.

So as people get older, they tend to lose muscle.

And when you do that, you become frail, and you lose functional capacity.

And then that starts off a vicious cycle.

Once that happens, then you're less likely to be physically active.

And then, of course, when you're less physically active, your muscles begin to waste away more and it's very debilitating.

So I think as we get older and I'm getting older, it's more and more important to incorporate that.

So I think that's the 1 thing that I've taken to heart.

From what you said there, it sounds like not doing resistance training, not lifting weights as you age, almost accelerates aging in any sort of superficial sense.

But also in a physiological sense, you're increasing the speed of aging.

Yeah, I'm not sure if I'd think about it that way, but I think I'd kind of reverse it slightly, which is that aging is just the clock ticking off, right?

There's nothing we can do about age, but senescence is the way our bodies degrade as we get older.

And what physical activity does, in fact, maybe the most important thing about physical activity, is that it slows senescence, especially for certain organs and systems.

And there are different kinds of physical activities.

So there's endurance physical activities, you know, like running, walking, et cetera, swimming.

And then strength or resistance physical activities.

And they have different kinds of ways in which they slow various properties of senescence, which we colloquially call aging.

And I think 1 of the things that's really interesting about humans, in fact, I think it may be the most important thing about this book, and you asked about myths earlier.

The most important myth, I think, by far, is this idea that as you get older, it's normal to be less active.

We evolved to live, 1 of the things that's most interesting about humans, maybe, is that we evolved to live about 20 years or so after we stopped reproducing.

No other animal does that except orcas, maybe killer whales.

But with the exception of killer whales, humans have this really weird life history.

But grandparents in the old days weren't, you know, retiring to Florida or I don't know what they do in England or whatever, go to Mallorca or whatever, and kick up their heels and play golf or whatever with carts.

Grandparents in the olden days, right, or in many cultures still today, are working, right?

They're working in the fields, they're hunting, they're gathering, they're getting food for their children and their grandchildren, they're helping with childcare.

And that physical activity, that's what their job is, to be physically active.

But in turn, that physical activity turns on an amazing suite of physiological processes that counter aging.

Turns on repair and maintenance processes that not only keep our muscles strong, but also keep our DNA from accruing mutations, keep our mitochondria numbers high, keep the cells in our brain from accumulating gunk so that prevents Alzheimer's and other forms of dementia.

I mean, for every system of the body, physical activity has benefits that slow the aging process.

And so when you stop doing it, you accelerate, and that's the way in which you perceive it as accelerating aging.

But really it's the absence of physical activity which lets aging run amok.

In your first book in 2013, the story of the human body, in chapter 12 you said, you use this phrase, use it or lose it, basically.

And I was sat with someone recently, and I was trying to figure out why it appears that when people retire, or the other instance I've seen is when their elderly partner passes away, it appears as if they don't live much longer.

It's kind of like folklore or something that once you retire, your days are kind of numbered.

And I was trying to figure out the evolutionary reason for that, but it sounds like that's kind of what you've explained there.

Well, I mean, I think part of that is depression, right?

When you lose a partner, I mean, grief and depression, your cortisol levels go up, your immune system goes down.

I mean, psychosocial stress plays a serious physiological toll.

But also, as you just pointed out, when people retire, they become less active.

And that loss of activity has enormous effects on every aspect of our body.

And our minds, physical activity is important not just for physical health, but also vital for mental health.

And I think a lot of the problems that, a lot of mental health issues we have today, depression, anxiety, some of them, to some extent, we can attribute that to less physical activity.

And as people age, becoming less physically active, again, makes them much more vulnerable to a wide suite of diseases.

Well, or if you do retire, I mean retiring is again another modern weird thing, right?

Nobody retired in the past I mean if you're a farmer, it's like a subsistence farmer and name it any place, right?

It's not like suddenly you hit 65 and all of a sudden you no longer have to work in the fields.

You work in the fields until you're dead, right?

They continue to be physically active until they die, right?

But you, of course, can replace work that you do with challenging, rewarding, fun things to do.

The important thing is just not to stop being physically active.

1 of my favorite studies ever published, without a doubt, is a study done by a guy named Ralph Paffenbarger.

He realized that places like Harvard are fantastic for studying aging because Harvard, like other private universities, never lets go of their alumni.

So until the day you die, they're asking you for money on a regular basis.

And so he got the Alumni Association, the Harvard Development Office, to let him follow a series of Harvard alumni from several years and keep asking them questions about their physical activity levels and also their diet and whether they smoked and stuff like that.

And then you track them for 25, 30 years.

And what he found was that the alumni, we have to correct it for every factor you could think of, that as the alumni got older, the effect of physical activity on their health outcomes was bigger and bigger.

So alumni who were in their 20s, 30s, and 40s, for example, who were exercising 4 or 5 times a week, they had about 20% lower death rates.

By the time they got to their 60s and 70s, the alumni who were exercising more had 50% lower death rates.

So as you get older, so what, and this has been replicated again many times, but what he showed was that as you get older, exercise becomes more, not less important for maintaining your health.

Been thinking a lot about this because I was saying to Jack, my dad is 60-ish, but he's very, very out of shape.

And I was in Indonesia and I was with my girlfriend and we went and we were going white water rafting.

So we had to go down this really big hill.

With all these stairs, it was like 300 meters of stairs.

And I remember just thinking, my dad wouldn't be able to do this at his age at 60.

And I want to be able to go down those stairs when I'm his age, because at the bottom of there was a fun activity with someone I loved.

And to think that I'll get to a point in my life where not so far away in the grand scheme of things, where I won't be able to go up or down some stairs because I'm 60, because of my sort of genetic predisposition as I saw it was quite sad, but having heard you say that, it really feels much more like a choice than it is genetics.

Yeah, look, we have this expression in my field, which is that genes load the gun and environment pulls the trigger, right?

Some of us have genetic predispositions towards being more likely to get diabetes or heart disease or this or that or the other, but our great, great, great grandparents in different environments weren't getting these diseases or they were getting them at much, much, much lower frequencies.

It's not because they were dying earlier.

It's because these diseases were less common.

So I think we too often blame our genes for many of these diseases, many of these health problems.

And I'm not in any way denying the role of genetics, but that environment is way more important.

And we have control over our environment to some extent.

And so if you want to reduce your risk of cardiovascular disease, reduce your risk of diabetes, reduce your risk of Alzheimer's, dementia, exercise isn't a magic bullet.

It's not going to prevent you from getting those diseases completely, but it lowers your risk quite substantially.

I mean, we have an immense amount of data on why that's the case.

For every single 1 of these diseases, we understand the mechanisms by which physical activity has important mechanistic effects on these diseases.

So there's epidemiological data, there's mechanistic data, there's personal data.

The problem is that it's hard to do, right?

It takes willpower to overcome the inertia of doing what's completely normal, which is wanting to take it easy.

I just flew yesterday from Denver to Boston.

And in the airport, there are these escalators right next to the stairway.

And the escalator and the stairs, it wasn't a huge stairway.

Everybody's lining up to take the escalator, and the stairs are totally free.

So I, being me, of course, I'm not allowed to take the escalator unless I have to, right?

So I run up the stairs, but those people taking the escalator, there's nothing wrong with them.

It's an instinct to take it easy when you can, right?

And we now live in a world where everybody can do that, because we have escalators and lifts and cars and shopping carts and all these wonderful devices to make our lives easier, and now you have to overcome this fundamental basic instinct to take it easy in order to be physically active.

And so, and furthermore, if you're unfit and you're not really, exercising isn't any fun, right?

You sweat and you get hot and you get cranky and it's not that rewarding until you get fit.

See all The Diary Of A CEO with Steven Bartlett transcripts on Applepodcasts

E263: Harvard Professor: "10,000 Steps A Day" Is A LIE! Revealing The 7 BIG LIES About Exercise, Sleep, Running, Cancer & Sugar!!! Daniel Lieberman