[MUSIC PLAYING] PETE WILLIAMSON: Hi. My name is Pete, and
I'm your host today. Dr. Dan Lieberman
is a professor of human and evolutionary
biology at Harvard University and a pioneering
researcher on the evolution of human physical activity. He's here to discuss
his book Exercised: Why Something We Never Evolved
to Do Is Healthy and Rewarding. People watching the talk will
see a YouTube chat window over to the right. If you type your
questions into the chat, we'll have time for a short Q&A
after the main presentation. And we'll get to as many
questions as we have time for. So this is what the
book looks like. And please welcome
Dr. Dan Lieberman. DAN LIEBERMAN:
Thanks for having me. So shall I get started? PETE WILLIAMSON: You're
very welcome, yeah. Please go right ahead. DAN LIEBERMAN: All right. Well, I'm going
to share my screen and use some slides to
talk my way through this. So it's a real
pleasure to be here and to talk about this
book I just published. It came out last
week, Exercised: Why Something We Never Evolved
to Do Is Healthy and Rewarding. And I thought I'd
start by imagining that this audience
is representative of the US public in general. And if that's the
case, about 20% of you probably got 150 minutes of
physical activity a week, which is the recommended minimal
dose by every major health organization in the
world-- the American Heart Association, the American
College of Sports Medicine, the US Surgeon General, et
cetera, et cetera, et cetera. But the other 80% of us
didn't get 150 minutes a week. And that's just 21
minutes a day, right? And those of us who do didn't
are often confused about it, and ambivalent, and anxious,
and feel shamed and nagged, and fed up with the whole talk. And so if you're one of those,
you, probably the last thing you want to do is to see a book
about exercise and somebody promising you 70
easy steps to get ripped to run a
marathon, or whatever, all that kind of stuff. But I can assure you that
is not my goal today. What my goal today,
really, is to do is to make all of
us less exercised about the term exercise,
about the nature of exercise. And the pun is
very much intended, because exercised and exercise
come from the same root. Before I go any
further, though, I want to thank various folks
who helped with this book-- my amazing editor, Erroll
McDonald, and my agent, Max Brockman. And there's a whole suite
of colleagues and students who've helped out in all
kinds of different parts of the-- this book and
read various chapters. I especially want to shout
out to my wife Tonia, who read the whole thing
from beginning to end, and my colleague and running
buddy and collaborator in research, Aaron Baggish,
who also read the entire book-- and we talked about
it on endless morning runs-- and various other folks
who help in all kinds of ways. I don't have time to thank
them all individually. But really, I'm really
grateful to all of them. OK. So the next 30 minutes
or so, I thought I'd briefly talk a little bit
about why I wrote the book and what it's about. And then, I'm going to give
you several examples about some of the myths of exercise that
I think make people exercised about exercise
and explain a very strange modern, industrialized,
commercialized, medicalized approach to something
very natural. And I know it's a cliche. But cliches are usually
cliches, because they're true. And I really was
one of those pint sized nerdy kids who was
picked last for every team. When I was a kid, I was
very ashamed of my body. And I didn't feel very athletic. And I once actually
hid in a closet during gym to
avoid going to gym. And you can name every
cliche you can think of. But that was me. I never thought I would
become a somebody who would ever even work on this topic. But I did have an amazing role
model, and that's my mother. Here's a picture
of her recently. And that's, by the way,
not a picture of her when she was younger,
my father actually who takes lots of
photos for some reason never took a picture
of her running, because I guess maybe they
were running together. But when my mother
was a young professor at the University
of Connecticut, they built a fancy new gym. And they wouldn't
let women use it. And so she was so
irritated by that. She started to run in
order to liberate the gym. And she couldn't run even
more than a quarter of a mile at first, but she slowly got up
to a half mile and then a mile, et cetera. And she did liberate
the gym, by the way. And she also became
hooked on running and ended up running five miles
a day for about five decades. She's still alive, and kicking,
and very healthy, and vigorous, and exercises every day. And I attribute part
of that to the fact that she was so physically
active for most of her life. And so I grew up thinking it was
normal to be physically active. But I was a-- I didn't-- that's not
what I studied, right? I became a head guy, actually. So most of my career, I
worked on skulls, and heads, and why the human
head is the way it is. And I got interested in
the topic of running, because I got interested in how
and why we hold our heads still when we run. So humans are like pogo
sticks when we run. We bounce up and
down on two legs, and our heads are
at the top of it. But most animals like
this pig here, quadrupeds, and they can flex and
extend their necks. And so we got
interested in this topic of how humans can hold their
heads still and keep it from joggering around
when we exercise. And we thought there was this
interesting structure called the nuchal ligament,
which is a-- these have trace in
the fossil record. And that led to my
colleague Dennis Bramble and I writing this
paper in nature in 2004 entitled "Born
to Run," in which we made the argument that humans
evolved to run long distances. And we've been doing that
for several million years. And because of that, I got
interested in barefoot running. Because if humans evolved to
run millions of years ago, we obviously did it barefoot. And I was curious
about how people used to run before the
invention of modern shoes. And all that basically got
me interested in the field of evolutionary
medicine, which is the application of
evolutionary theory and data to health and disease. And it's a fascinating growing
and I think a very important new field. And it led me to write a book-- my last book, my previous book,
which is The Story of the Human Body, which I published in
2013, which is really about the concept of mismatch
or the theory of mismatch, which is that most of
the diseases that we-- that get us sick and kill us-- COVID being an exception-- are our result from our
bodies being inadequately or imperfectly adapted to
modern environmental conditions. So flat feet, and myopia, and
heart disease, and diabetes-- and the list is
very, very long-- many cancers-- Most of
us who are in this room or who are watching
this talk at least are going to get sick and
die from a mismatch disease. So it's pretty important. So anyway, I was thinking
about mismatch diseases. And I was finishing
up that book in 2012 when I went to do some fieldwork
in the Sierra Tarahumara, which is in Chihuahua in
northern Mexico. And I was doing research among
the Tarahumara Native Americans who are well known for,
among other things, their long distance running. It's really beautiful place. And I was driving
around on a pickup truck to these really remote pueblos
and measuring people's feet and talking to folks and
being a good anthropologist. And I had my list of questions
I was asking everybody. And I expected to see people
running everywhere barefoot and-- But actually didn't see anybody
running anywhere at all, except I asked them to. Nobody was barefoot. But then eventually I
got to visit and see one of the amazing
races that they do. In fact, there were
two races I saw. And I've now been
several times, and I've seen quite a few of these. But the first is it was actually
a double header that day. So it began with what's
called an ariwete, which is the women's race, which the
women have a cloth circle which they flick with the sticks. They chase it, find
the cloth circle. And they flick it again. And they run, and they flick,
and they run, and they flick. And they do about 25 miles. It's a beautiful race
and gorgeous to see and impressive
running abilities. And then, the men's
race starts after that. That's called a rarájipari,
in which instead of a wooden-- a cloth circle, they
have a wooden ball, which they flick with their feet. And then, they find it,
and they run to find it, and they flick it again. And they run, and they flick,
and they run, and they flick. And they do it. And this particular race
went on for about 50 miles, really amazing race. And I was, of course, very
impressed by these races, but also interested by
the fact that only a few of the Tarahumara
were doing this. The vast majority were
just watching, like me. I did run along
with them, actually, a little bit at night. And so I got a chance
to measure an interview and talk to some of
the-- to runners. And one of them
was this guy named I'm going to call him Ernesto. He was in his 70s. And this is actually a picture
of him in the rarájipari. I was taking a video of people. And I was trying to talk to him,
and asking about his running and whatever, and asked
him about how he trained. And I had been asking
everybody this question. And the woman who was
helping me interpret, because I don't speak the
native Rarámuri language, was really struggling to get
people to answer my question, because it turns out
there's no word-- not only a word for training,
but the idea of training is foreign to the Tarahumara. A few of them are great runners. Most of them actually aren't. And so Ernesto,
eventually, when she explained that this gringo
who's talking to you goes for like a five mile
run every morning to practice his running, he asked me-- and I'll never forget
this question-- but he said, why would anybody
run if they didn't have to? And of course, it dawned on
me that running is weird, actually, for-- just
for the sake of running and that physical
activity is a normal thing that people have been doing
for millions of years. Physical activity's
just moving, right? It's moving, expending
energy to move. But exercise is a very
special physical activity. And it's a modern strange
thing that people just haven't didn't-- do before, because exercise
is voluntary physical activity to sustain or improve
health and fitness. It's a modern abnormal behavior. Nobody did it until recently. People didn't go for five
mile runs in the morning just for the sake of it. People didn't buy weights whose
sole purpose was to be lifted. They were physically active,
because they had to be. Or they were physically active
when it was rewarding and fun, like for example dancing,
which the Tarahumara also do in beautiful ways. So to me, the apotheosis of
exercise is the treadmill. Just think about it. It's a really
weird thing, right? You spend thousands of dollars
to buy one of these things, or you go to a gym, pay-- I don't know how much
money you pay a week. Or maybe Google, it, provides
you with one of these things. But somebody paid a lot
of money for a machine that's loud, and
noisy, and boring, and sometimes treacherous. And you get nowhere at all. Right? It's really a bizarre thing. In fact, in our
research, because most of the research
I do is in Kenya, we've tried to bring treadmills
up into the area where we work. And if you've never been on a
treadmill for your whole life and all of a sudden
in your 40s or 50s, and somebody brings
up a treadmill and asks you to
stand on it, you're going to be very awkward. Right? It's a very strange
and unpleasant thing. And in fact, in case you
don't-- if you hate treadmills, you're not-- you're
in good company. Treadmills are actually
invented in the 19th century by the Victorians
to punish prisoners. They're invented by,
again, William Cubitt to keep people like Oscar
Wilde from enjoying themselves in prison. So on all, I think
today many people are exercised about
exercise, where they're vexed, and worried,
and anxious, and harassed. And no topic has really
introduced me more to this fact that people are exercised about
exercise than the barefoot running debate, which I got
involved with back in the day when we published our
research on barefoot running, because there was
this incredible debate about whether barefoot running
is better, or it's bad for you, and whether shoes
are good for you. And people, of
course, were worried about whether running
would ruin their knees, and how much they should run,
and how do you get motivated, and how much weights you
should do, versus cardio, and how much sleep should
people have, and is your chair out to kill you? And there's so many questions
that people are confused about in terms of exercise. And for the most
part, people just are unhappy about it, which
is expressed by the fact that 80% of Americans don't get
minimal amounts of exercise, even though the vast majority
of them would like to. So we're not obviously
doing very well. And as I said before,
the biggest problem is that the vast
majority of us are not getting our recommended minimal
dose of 150 minutes a week. Again, that's just
21 minutes a day. That's not a terribly
large amount. And I think the other problem-- There are other issues as well. We have become overly
focused on weight loss. We focus a lot on
elite athletes. But I think the other
problem with the exercise is that we have this
Western postindustrial bias. Almost all the
data that we get-- we have about physical
activity and exercise comes from studying
Americans and Europeans. And yet, that's like a
sliver of humanity, about 10% of the world, and
doesn't represent what we were like for most
of our evolutionary history. Right? So we have a very strange
medicalized, commodified, industrialized, Western view of
exercise and physical activity. And the result is that
that's surprising. Not surprisingly, I think we
have a very strange attitude towards it. And so I thought it would be
useful and helpful to write a natural history of physical
activity, including exercise. And there are really two
mantras which guide my book. And the first is that
nothing in biology makes sense except in
the light of evolution. And that's because our bodies
weren't engineered or designed. They evolved. And if you want to
understand why our bodies are the way they are, you
have to understand that evolutionary story. But we're also humans
with complex behaviors. And if you want to understand
something about behavior, you need to think about
that human behavior in the context of anthropology. And so the book weaves together
a lot of my own experiences. I've spent the last 15, 20
years traveling around the world seeing how people
use their bodies, but also using information
from anthropology, and various branches of
biology, and health science to tell the story, the natural
history, of human evolution. And I do so in four parts,
because you can't be physically active all day long. To understand physical
activity, you also have to understand inactivity. So the first part of
the book is actually about physical inactivity,
your resting metabolism, and sitting, and sleeping. And then, the next part of
the book is about speed, and strength, and
fighting, and sports that most animals
are really good at, but we're actually not
so good about that. But what we humans are
exceptional at is endurance. And so the next part of
the book is about walking, and running, and
aging, and dancing, and all kinds of other
endurance activities. And then, the final
section of the book is about how we apply
all that to modern health in the modern world. And so I talk about motivation,
and dose, and the effects of exercise on disease. And each chapter isn't
really about a myth. But I use some of
the myths of exercise with it for each chapter. And I'm not going to go over
all the myths right now, because I don't have time. But I thought it would be
fun for the rest of this talk just to highlight a
few of these myths and go into a little
bit of detail. And as I said before,
the biggest myth of all is that we evolved to exercise. And the way I think-- I like to think
about this is what I call the myth of
the athletic savage. We have this idea that-- and the modern world has
basically contaminated us in that if we hadn't grown up
with Nike shoes, and Gatorade, and cars, et cetera, we'd
be these incredible athletes able to run ultramarathons, and
dance all night long, and lift giant rocks over our heads,
who knows what, right? And it is true that until the
invention of modern machinery, if you were a hunter gatherer
or subsistence farmer, you basically had to
work for a living. And people engaged in lots
of walking, and carrying, and digging, and climbing,
and running, and dancing, and all kinds of
other activities. But it turns out it's
not a crazy amount. If you actually look at
what hunter gatherers do, in terms of moderate and
vigorous physical activity, it actually amounts
to only about a little over two hours a day,
about 2 and 1/4 hours. And so that's not an enormous
amount of physical activity. It's more than your
average American. But it's not a crazy amount
of physical activity. And just like us, they spend
most of the day resting. And if you look at when
they're physically active, they're active primarily when
it's necessary, in other words, to get food, or when they
find it socially rewarding, as in, for example, this
particular-- this dancing that you can see from the
hunter gatherers in the Kalahari Desert. So if you've ever been in
an airport, or a subway stop, or a mall,
or whatever, where there's an escalator
next to a stairway, and you have that little
voice in your head that says take the escalator. Now, obviously, there were no
escalators in the stone age. So there's nothing natural
about taking an escalator. But it is natural
to try to avoid unnecessary physical activity,
because until recently, energy was limited. People didn't have a
lot of extra energy. And so we had to
engage in trade-offs. Energy you spend on a five
mile jog in the morning, that's 500 calories. It's 500 calories that you're
not spending on the only thing that natural
selection cares about, which is having babies, which
is reproducing or taking care of your body. And so I think we
need to be more compassionate about this
basic instinct people have, which is to save
energy and not do unnecessary physical
activity, because it's a fundamental normal instinct. And we shouldn't
make people feel bad about that little voice. It doesn't mean you should
obey that little voice. But this woman who I
photoshopped going up the stairs is actually
being abnormal in a way from an evolutionary
perspective. So let's look at four
other myths, just-- And again, I've just
picked four of them. There are lots of stuff
in the book, of course. But I wanted to pick
four that I thought would be fun to talk about. And one is sitting, because
probably most of you right now are sitting. And we've all been told to
be terrified of sitting. Sitting is the new smoking. Your chair is out to kill you. And it's true. There's all kinds of
horrifying statistics you can read about
regularly in the newspaper. If you sit more than three
hours a day, explains about 4% of the deaths in the world. And an hour of sitting is
as harmful as the benefit of 20 minutes of exercise. And I could fill the screen
with various other horrifying statistics. And yet, if you go
and do what I do, which is travel around
the world and see how people use their bodies,
people sit all the time everywhere, in every culture. So the scene on the left
that you see is a Hadza camp. That's actually the picture I
took on my iPhone the second I walked into that camp. That's the first thing I saw
when I walked on this camp. And look, everybody's sitting. That's what they do. This is the elderly Tarahumara
gentleman, who's sitting, and people in the
village in Africa, where they're all sitting. People sit all over the world. There's nothing
unusual or normal-- strange about sitting. So actually, if you're
curious, this is a Google talk. I thought I would use Google
and ask how many hours a day do Americans sit? I did this two days ago, and up
came a whole bunch of answers. And you get like so
many different results. These are the top five hits. So one in four of us sits
for more than eight hours, which is not a particularly
useful statistic. According to one site,
we sit 15 hours a day. another site says
6.5 hours a day. Another site, 6.4 hours a day. Another site, 13 hours a day. How do we believe this? And who are these people? And is it self-reported data? What are the covariants? Was it on weekends or weekdays? Et cetera, et cetera. Of course, it's
really very hard. And in fact, there's a lot
of really bad data out there. And a lot of people
say all kinds of stuff. But if you look at
high quality data, where they put accelerometers
on people to actually measure what they're doing,
and you look at age and various other
sorts of things, and weekends versus
weekdays, it turns out that young Americans sit
around 9 to 10 hours a day, and older Americans tend to
sit more, about 12 to 13 hours a day. But there's an enormous
amount of variation, depending upon what
day of the week it is, and your age, and your sex,
and your socioeconomic status. And you can imagine other
kind of variables as well. Now, you may think
that Americans are sitting this ridiculous amount. But actually, it's no different
from hunter gatherers. A recent paper by some
colleagues and friends of mine actually just showed
that the Hadza, who are a hunter gatherer
population in Tanzania, sit about 10 hours a day, which
is about the same as Americans of the same age. So there's nothing
special about Americans in terms of how much we sit. But we do sit
differently, and that's where it gets interesting. So if you're living
in a population a part of the world where
there's no chairs, and that's where I work, for example, there
are no chairs with backrest. People sit on the ground. And so that means you
have to use back muscles, and they often squat. So they have to
use those muscles, and they often sit
intermittently. The average bout--
the average time that they spend sitting at a
given time is about 15 minutes. Whereas, we-- and I had to
put these two favorite people on the planet here up
on the screen here, but they look so
excited and happy. But we sit-- tend to sit
it chairs with backrests. And we don't have to use
basically any muscles to support our upper bodies. And Americans tend to sit
much more long-term bouts of sustained bouts, about
40 minutes for each bout. So we sit more passively. We sit less actively. And in fact, if you look at
the data, what it really shows is not that work time sitting
is all that bad for you. It's leisure time sitting. So various studies in Japan, and
in Denmark, and other countries have shown that negative health
outcomes are much more strongly associated with leisure time
sitting than work time sitting. So if you sit all day at work
but go home, and exercise, and walk to the
bus stop, and all those other sorts of things,
you're in pretty good shape. But if you work all day,
sitting, and then you go home, and you spend the
rest of the day sitting, well, then,
of course you're going to get into trouble. And furthermore,
the length of time that you spend
sitting in each bout is strongly correlated
with health outcomes, independent of how much
time you spend sitting. So people, for example, who
are sitting in long bouts without getting up,
30 minutes or more, have actually twice the
rate of all cause mortality than people who sit
in shorter bouts. So if you're going to sit,
get up every once in a while. Get up every 10 minutes or so. Sit more actively. Let's not say that sitting
is the new smoking. It's just not true. And by the way,
there's a whole section of the book on slouching. If you've been told that
you shouldn't slouch, it's basically all nonsense. It's we've been confusing
cause and effect. So to speak, bad
posture when you sit is actually more reflective
of whether or not your back is strong. But there's no evidence
that it actually causes higher rates of back pain. But you can check the book
out to read about that. So I think we should be less
exercised about sitting. It's not abnormal to
sit as long as you get some physical activity. Just sit actively
with interruptions and relax about your posture. If you slouch, don't
worry about it. OK. So another common myth is that
we evolved to be super strong. We have this idea
that cavemen are these ripped guys
with giant muscles, and they could lift giant
barbells over their heads and stuff like that. And that myth actually
goes back a long time. And in the book, I describe
this fellow, Paul Du Chaillu, who was the first Westerner
to travel to Africa and see-- and to see and describe gorillas
for the general populace. And here is a picture
of Du Chaillu lecturing in London about these
terrifying creatures, which he grossly exaggerated. And it's not unsurprising
that around the same time when people were first
finding the first skeletons of Neanderthals that the
Neanderthals were basically described to be a bit
like those gorillas. And since then, we've had
this idea that cavemen are ripped, super strong creatures. But actually, it's not true. And in fact, even our close
cousins, the chimpanzees, aren't as strong as people
often claim they are. Chimpanzees are about 30%
stronger than most humans. And most hunter
gatherers-- people have measured their strength--
actually aren't very strong. And furthermore, it's
actually not even good for them to be super
strong, because muscle is really expensive, right? But the thing that's
important about them is that whether or
not super strong, they tend to keep it
up with their age. So this is a
measure, for example, of grip strength in
England for men and women, compared to a group of foragers
in the Amazon, the Aché. And you can see that the Aché
basically are track with 75th percentile for men
and for women as well. But what's really
cool about them is because they stay very
physically active as they age, they tend to-- they tend not to lose strength
that much as they get older, a little bit of
course, which means that they avoid
sarcopenia, which is really a dangerous disease. That's muscle wasting, which
is a really important cause of frailty. And it causes a vicious circle. And the reason for
that, of course, is that muscle is
costly, as I said. If you're a typical scrawny
human like me, about 30% of your body is muscle mass. And that accounts for about
20% of your metabolism. Now, if you bulk up
to be like this guy, and you have about 40% of
your body's muscle mass, you need another 200
to 300 calories a day to pay for all that extra
muscle, which basically-- well, maybe it looks good, but it's
not going to really benefit you if you're using weapons to
hunt, or gathering berries, and that sort of thing. So it's actually a cost. And that's why we have this
use it or lose it phenomenon. It's adaptation to gain
strength when you need it and lose it when
you don't need it. But now, today, when
we-- people live these lives of
physical inactivity, and they don't really
have to do much strength, it becomes a mismatch. And that's why
many of you may be aware of how Ruth
Bader Ginsburg lasted till she was 87
strong and vigorous, because she went to the
gym several times a week and stayed strong. And so as you get
older, strength training is unquestionably a really
very important to do about twice a week. So we should stop being
exercised about strength. It's normal to just be
only moderately strong, but it's also important
to keep it up as you age. And you don't need,
by the way, to go through this no pain,
no gain nonsense to maintain your muscle mass
and keep your bones strong. That's, if you want to look like
Arnold Schwarzenegger, fine. But for the rest of us,
that's completely unnecessary. So another myth out
there is that you can't lose weight walking. And walking is
important, because it's by far the most fundamental
form of physical activity. Humans evolved to walk. That's what we are. We're basically
apes on two legs. And around seven
million years ago, that was the big
shift that set us on a-- shift that set us on
our evolutionary trajectory. And the average hunter gatherer
woman walks six miles a day, and the actual average man
walks nine miles a day. So typical hunter gatherer
women are basically walking from like LA to
Washington D.C. every day-- every year. That's an amazing
normal, but normal fact. That's just normal to
walk across the country, basically, that many
miles every year. But it turns out
that that's become a little bit controversial. And recently,
there's been a trend to tell people not to bother
walking or even exercising in general for weight loss. And the idea is that dining
is much more effective than exercise for weight loss. And in many respects,
it's completely true. If you walk a mile, you spend
about 50 extra calories, which is way less
than most of the foods that we crave after exercise. So if you got a bunch of fries,
that's about 365 calories. You're going to wipe out
any gains that you made. So we have what's
called compensation. We eat. We eat more when we're hungry. We're hungry, we eat
more after we exercise. And there's also some
intriguing evidence that physical
activity can affect your basal metabolic rate
and actually lower it. But part of the problem
with this argument is that a lot of the data
on the effects of walking are based on that 150
minutes minimum level of physical activity
that's often recommended. Again, that's the US Surgeon
General's recommendation for how much physical
activity you should get, which only about 20%, 25%
of Americans actually get. So that's just 21 minutes a day. So basically, it's a mile a day. So if you actually get people
to walk about 21 minutes a day, they can lose about--
if they don't compensate by eating extra food, they
can lose about a half a pound a month, which can translate
into about six pounds a year. And if your average
American is trying to lose 50 pounds, sure enough. That's just not very effective. You're much better
off dieting, then, if you want to lose weight. But if you took a-- take a more evolutionary
normal dose, let's just double that
to 300 minutes a week, which is just 40 minutes
a day, still way less than your typical
hunter gatherer. You can lose a pound a month,
which is 12 pounds a year. And there are plenty of
randomized control studies which show this is the case. So you're not going to lose
huge amounts of weight super fast by exercising. But you can lose
moderate amounts over long periods of time,
which is very healthy. And even more importantly,
physical activity is not so important
for losing weight. What is really important for
is preventing weight gain or weight regain. Here's an example of
an experiment done here in Boston on policemen. And they put policemen
on a really hard diet for like eight weeks. And some of them dieted. And some of them dieted but also
had to do a serious exercise regime. And you can see that everybody
lost a lot of weight. But the ones who exercised
lost a little bit more weight than the ones who just dieted. Makes sense, right? But the key thing is that
after the dieting was over, the dieters, just the
dieters, stopped their diet. And they weren't exercising,
and they gained all their weight back. But the ones who were on the
diet and exercise routine and kept exercising were able
to keep all that weight off. And study after study
has shown the same thing. Do you want the real
full benefits of a diet? Don't skimp on the
exercise, and especially don't skimp on the
exercise after the diet. It's your key to
keeping the weight off from coming back again. So let's stop being
exercised about walking. It's the most fundamental form
of human physical activity. And it should be an important
component of every weight loss program. And then, the final
myth I want to mention is that it's common
that we think about in our Western world
that it's normal to be less active as we get older. We retire. We move to Florida. And it's true. And modern Americans get way-- if we're less-- if we're
not very physically active in our normal
middle age, boy, do we get physically
inactive as we get older. So according to a
recent big study of thousands and
thousands of Americans, using accelerometers,
so people in their 20s were engaged in about 24
minutes of moderate and vigorous physical activity a day. And by the time
they're in their 60s, that's in half to
about 12 minutes, which is not a hell of a lot. But I think that's actually
a very abnormal thing, because back in the
stone age, people evolved to be physically
active as they got older. In fact, humans are
unusual in that we evolved to live after the age
at which we stop reproducing. So hunter gatherers,
if they survive childhood, and
infectious diseases, and diarrhea, and
things like that, they actually typically
live into their 70s and/or sometimes their 80s. So they're living
about two decades after they stop reproducing. And they're not going
into retirement. They're actually working
hard as grandparents, foraging and
hunting, and getting honey and all kinds
of other things, and helping out their children
and their grandchildren. So if you actually
look at this study by a Kristen Hawkes
company-- and Kristen Hawkes is the person who proposed first
the grandmother hypothesis-- mothers in these
foraging societies are actually working
2 to 5 hours a day getting food for their kids. Whereas, grandparents are
actually working 48 hours. They're actually working harder. And that's important, because
the stresses of physical activity, the reason
exercise is healthy-- and I go into extraordinary
detail in the book about this-- is that exercise is stressful. Physical activity is stressful. And it causes stress to your
bodies in all kinds of ways. But that stress then turns
on repair and maintenance mechanisms, which then
clean up the mess. And in fact, like cleaning
up a spill on the floor, you often make the floor
cleaner than it was beforehand. And the same is true. So when you exercise, you're
producing antioxidants and anti-inflammatories. And you're repairing cells. And you're repairing your DNA. And you're producing all
kinds of growth factors for various organs, like
your muscle, and your brain, your liver, and your bone. And the list goes
on and on and on. Plus, you're also
burning belly fat, which is very inflammatory. You're lowering your blood
sugar, and levels of blood fat, and cholesterol. And again, the
list is very long. So the important thing
is that as we get older, physical activity becomes
actually more important. And this was shown
really clearly in this wonderful study. This is the first
big epidemiological study of the effects of exercise
on aging by Ralph Paffenbarger. It was done on Harvard alumni. And he did that
because he figured out that universities
like Harvard are fantastic places to
study this problem, because they never lose
contact with their alumni, because they're always trying
to get money from them. And so we convinced the alumni
office to let him get data on the alumnus on what their
physical activity was like, and then waited for them to die,
and then showed that for-- when alumnus were less
than 50 years old-- they were the ones who were
exercising a reasonable amount, 2,000 calories a week-- had 21% lower all
cause mortality rates. But by the time they
got into their 70s, the ones who were exercising
2,000 calories a week had 50% lower all
cause mortality rates. And this has been shown over
and over again in other studies. And it's also been shown that
it's never too late to start. If you're sedentary
when you're young, and you pick up exercise
as you get older, you still get a
lot of the benefits of the physical activity. And importantly, it
doesn't really matter-- There's no one dose. Any exercise is
better than none. This is a very important graph. This is the dose
response curve of minutes per week of moderate to
vigorous physical activity against the relative risk of
death for a sample of well over a million Americans. And you can see that
if you exercise just 60 minutes a week, moderate to
vigorous physical activity, you lower your
relative risk of death at a given age by about 40%. And as you get to
150 minutes a week, which is the standard
recommendation, you go down to about 50%. And additional
amounts of exercise continue to drop the curve. And eventually, of
course, it levels out. So any exercise is good. And even if you just
do a little bit, it'll give you
enormous benefits. So of course, there's
a lot more topics. I've only covered
just a smattering of what the book is about. But I hope that the book
informs, and entertains, and enlightens folks. But more importantly,
I would hope that it changes the
way we think about exercise, in particular in the
science of health in general. I think we've oversimplified
a lot of health information. And I think it's the information
we get is also heavily biased. It's biased towards
being Western. And it's often biased
towards elite athletes. And it's biased
towards weight loss. And it's heavily
commercialized, and medicalized, and judgmental, and
uncompassionate. And as a result,
it's not surprising that the vast
majority of Americans just don't like being nagged
and harangued about it. And it's not succeeding in
helping them get off the couch and be more physically active. And so I argue in
the book that, we, by using an anthropological
and evolutionary approach, we can help make exercise
more fun and more necessary and also help people figure out
how to make it more rewarding. But most importantly,
I hope that the book helps people enjoy
being active and helps us be less exercised about it. And with that, I'd be delighted
to take some questions. PETE WILLIAMSON:
So let's go ahead and go to the first
question from the comments. So Steve Stepanian
says, what are your thoughts on
prolonged fasting and intermittent fasting? DAN LIEBERMAN: Ooh,
great question. So intermittent
fasting is actually one of the few
non-exercise interventions that's been shown there's
pretty good medical data that it has health benefits. And the reason I
think it's beneficial is actually it turns on a
lot of the same responses that physical activity
does, because when you're in-- when you're doing
physical activity, you're in what's called
negative energy balance for a long period of time. You're using more energy
than is coming in, obviously, unless you're gobbling
huge amounts of donuts while you're running
or whatever it is. But so you're in
negative energy balance. That's a stress. And you have to draw
on energy stores. And that activates all
kinds of genes and cascades that turn out to have
a lot of benefits. It turns out that intermittent
fasting, essentially-- intermittent fasting turns on
a lot of those same processes. And I think, again, it's because
of negative energy balance. So of all the ideas out there
about easy ways to get healthy, intermittent fasting
seems to be the one that has the most evidence behind
it, apart from exercise. And I don't think
that's uncoincidental. That said, there's not
a lot of good data. And there's no good data
about the interactions between intermittent
fasting and exercising. And I believe, I suspect
when the studies come out that exercise will be shown
to be a lot more generally beneficial than
intermittent fasting. And if you're into
exercising a lot, you don't really want
to go through a lot of intermittent fasting. The two are incompatible. I like to run a lot. And there's no way I'm going to
go through long periods of not eating food, because I'm
just going to run out of gas. So I don't like to
do it very much. But great question. Thank you. PETE WILLIAMSON: OK. Next question from
Will Nicholson. Thanks for giving this
talk, Dr. Lieberman! Have there been any
significant developments since "Born to Run" for or
against the endurance running hypothesis? DAN LIEBERMAN:
Well, obviously, I'm biased, because I'm the author
of the endurance running hypothesis. But I would say-- I think I can say quite
without being unfair to others. But there's just been a mountain
of evidence to support it. We now have genetic data. We have genes like
the Cmah gene, which gives genetic evidence. We found so many
different aspects of physiology, and
anatomy, and biology, which predicted by the
endurance running hypothesis. I don't think it's actually
very debated anymore. It's entered the literature. It's a strange thing,
because in science, we spend most of our time trying
to prove each other wrong. So I think some of the arguments
about endurance running have been really more
about just how important it was in human evolution. And we never argued
that humans evolved only to run long distances. Of course, walking still
is really important. And not everybody ran. But I don't think humans could
have become scavengers and then carnivores without running. And the traces in our bodies,
vigorous physical activity is really important for us. And we have all
kinds of adaptations, which make no sense without
thinking about running. And they can't be
explained in any other way. So I think it's a pretty
resilient hypothesis. I'm going to stand by it. PETE WILLIAMSON: OK. Next question from
Lisa Takehana. On the topic of dieting
and caloric intake, how does cooking
or baking affect the caloric value of food? And how does it affect the
macro and micronutrients? DAN LIEBERMAN: So this has
been an interesting topic. This is a good
example of how people misuse evolution information. There's a lot of data on-- People have been
studying raw foodists, like people who think that
it's abnormal to cook our food. And the answer is you cannot
be a human being in most parts of the world until very,
very recently when-- unless you go to Whole
Foods and stuff like that-- and survive as a raw foodist. Cooking increases
your-- the availability, the bioavailability,
of most nutrients. You get more calories
out of cooked food. And also, you get more
macronutrients out of them. Most of the arguments
that cooking destroys the nutrient
quality of food are just completely falsifiable. In fact, humans are
so consistently-- Every human society
cooks a lot of its food. And it's pretty
clear that if you-- The only way you can get
away with being a raw foodist is eating really
high quality food that has had most of the
fiber removed from it already. These are domesticated foods. There's no way you could
be a hunter gatherer, eat a wild diet, and
not cook your food. You'd die quickly. It's not sustainable. If you want to look
more up about this, my colleague Richard
Wrangham and Rachel Carmody, both at Harvard, have written
extensively on this topic. And they're much more-- much greater authorities
on this topic than I am. PETE WILLIAMSON: OK. Next question from Mike Digman. Hi, Dr. Lieberman. Exercise and dieting both seem
important to overall health. However, calories
in and calories used need to be balanced. How do hunter gatherers
know when to stop eating? DAN LIEBERMAN: Well, it's not
a problem for hunter gatherers, because they're-- they-- they-- First of all, they work hard. And they don't have huge
amounts of excess calories. It's not like they go on diets. I think one of the funniest
moments in my life-- Once, we were with
some Hadza, and we were at the end of our trip. And we decided to cook up every
last little bit of food we had and have a big feast. We had every little bit of every
rice grain we had left in camp, we cooked, and all the bread. And the cook we had with
us made a-- he made a cake, and he smothered it in jam. It was a high calorie meal. And I have never
seen people carboload like that before in
my life, because they were so excited to get all
these great high energy carbohydrates, because
until recently, people went through cycles of positive
energy balance and then negative energy balance. And when you're in positive
energy balance, of course, you store fat, but then you're
going to take it back later, use it later, when
you're physically active, when you're nursing. The average mother nursing is
spending 500 calories a day to pay-- to synthesize all
that breast milk. It's expensive. So hunter gatherers
need that, to store fat, so that they can then
use it for times of-- for times of when food
availability is low, and they're at negative
energy balance. So hunter gatherers don't diet. They don't restrict
their food intake. They just eat as much as they
can, because what they eat is actually what they need. And levels of obesity
and overweight are essentially
nonexistent among them. So the problem is that today
we live in a world of plenty. We live in a world
where all of a sudden, we can get all the rice,
and cake, and shortbread, and fried chicken,
and whatever it is you happen to like that you want. But we never evolved
to curtail our intake. And now, we have to do
something really as abnormal as exercising,
which is to choose to eat low calorie foods. Imagine explaining to your
great great grandparents that you pay more
money for foods that have had the fat and
sugar removed from them. That's pretty weird right. That's very abnormal. That's a very modern thing. PETE WILLIAMSON: OK. Next question from James Newman. As you say, we evolved to avoid
unnecessarily expending energy. How do you recommend we
counter this instinct and find motivation to exercise,
given that fact? DAN LIEBERMAN: Thanks
for asking that question. So chapter 11 in the book
is entirely on that topic. And so I can't do
it full justice. But I think there
are several ways. As I said before,
I think that we evolved to be physically
active for two main reasons, for when it's necessary and
when it's socially rewarding, when it's fun. And so I think the solution
to motivating people, and if you look at the
evidence, is that Fitbits don't work so well. Sorry, folks. Prescriptions
don't work so well. Being nagged and bragged
at, it doesn't work so well. But what does work
well is when-- is social reward. So I think one way is
to make-- is to treat exercise more like education. Think about education,
which is equally abnormal. We never evolved
to go to school, and learn algebra,
and learn to read, and do all those
sorts of things. So how do we make school-- how do we get--
how do we encourage people to learn things? Well, we make it fun. University's and school's fun. It's social. You see your friends. Of course, now in
the COVID era, it's very unfun, as we all know. And we also make it
rewarding in other ways. People pay like $60,000,
$70,000 to go to my university and have me torture them. And I make them
do all this stuff. And then, I grade them
and give them a low grade if they don't do it
to my satisfaction. And they're paying for
the privilege of doing it. It's a commitment contract. So commitment contracts
are another effective way. Some of you may know
the website stickk.com, with stick with two k's .com. And a friend of mine actually,
she wanted to walk more. She wanted to exercise more. So she gave stickk.com $2,000,
made her husband her referee. And if she doesn't walk, I
can't remember how many miles a week, like 10 miles a week,
the website automatically-- and her husband
doesn't affirm it, the website automatically
gives $50 to the NRA. And it's been an incredible
motivator for her to stick with her
exercise regime, because she hates the NRA. And so she's kept with
her exercise regimen. So that's another
way of doing it. I think a commitment
contract is effective, making it-- treating it more
like education is effective. But for me, I think it's most
effective by making it social. I run with friends. I have a running buddy
who I have to meet tomorrow morning at 6:00 AM. And I can guarantee
you tomorrow at 6:00, I do not want to be out there. It'll be cold. It'll be dark. It'll be miserable. I'd rather be in
bed with my wife. But I can't leave him out
there in the cold on the corner of Mass Ave at 6:00. So I'll have to get out
of bed, and I'll grumble. And for the first mile, I'll
be really pissed off at it. But eventually, I'll
warm up, and I'll be-- And by the time we get home, I'm
sure I'll be in a great mood, and I'm glad that I've done it. So I think people are
good at exercising are good at finding
ways to make it social. And the sociology of it, like
dancing, and Zumba classes, or whatever you
can come up with. People are doing all kinds
of creative things on Zoom now in the pandemic. Those are over and
over again have been shown to be the
most effective ways to help people exercise. But instead of-- Because we treat exercise as
something like cod liver oil. You get on your treadmill,
and you do your 20 minutes. And you listen to
some podcast, which makes it mildly tolerable. If that's OK for you, if
you like that, that's great. But it's clearly
not that enticing for the vast majority
of human beings. PETE WILLIAMSON:
So if I could jump in with a quick follow-on
question to that. You said like getting together
with your running buddies. But right now, we're in
the middle of a pandemic. How safe is that? Is that safer than
not exercising at all, or staying at home? DAN LIEBERMAN: Yeah. I'm not an expert on COVID. So I don't really know. It seems to me that there's
very little evidence that people transmit the disease outside. What I've been doing-- And again, I'm not a doctor,
so I can't give this advice. But I've been wearing a
mask, and being careful, and trying to maintain
some social distance. And I also get tested regularly. So that helps. And as does the
person I run with. So he's a physician. So I relaxed about it. But you've got to figure out
what you're comfortable with. But certainly, it's been harder
to do that during the pandemic. It's a real challenge. But I should also
mention that there's a lot of data which shows that
physical activity is really important for priming the
immune system to fight respiratory tract infections. And COVID is an RTI. It's a respiratory
tract infection. It upregulates the number
of the cells that are your first line of defense-- they're called natural
killer cells; some of them are called cytotoxic T cells-- and also redeploys them
to the linings of the lung and another very vulnerable
locations in the body. And there's a fair
amount of evidence that moderate levels
of physical activity boost your immune system and
also boosts your antibody production as well. So when you get the
vaccine, go for a run. And the big debate
really is whether or not too much exercise
is problematic. So there's some
evidence-- there's been some arguments
that if you get excessive amounts of exercise,
you use so much energy. You deplete the energy that's
available to the immune system. And you depress it. And that's very debated. And I think if I were-- I'm being cautious. I'm trying to be careful about-- I'm not running
marathons on regular-- regular-- regularly. And I'm careful
afterwards, so I-- assuming that I'm
vulnerable to infection. PETE WILLIAMSON: OK. Thanks. Let's move on to
the next question. So it's Michelle Pham. Dr. Lieberman, we're
seeing such an uptick in fitness and health
technology devices and services. What do you think
the next frontier will be for this sector? DAN LIEBERMAN: That sounds like
a very Google-ish question. I don't know. I don't know. It's fun. Some of these fitness
apps and devices are fun. I have a GPS watch. And I check my
iPhone, which is very depressing during the pandemic,
because my step count has really decreased,
just because I'm not walking around town as much. But I'm still running
a fair amount. I think the big question
is really to what extent you can use these fitness
apps to actually change people's behavior? And there's some evidence
that there's some benefit. But there's not been
the huge massive benefit that I think that we
were initially told. If I were in your guys' shoes-- and if anybody wants to talk
to me, I'd be happy to-- I think that really the
way to use social media and to use some of
these apps is not to focus so much on
giving people information about how much
they're exercising, but to work more on the
social side, to help people-- help people have more fun. And my Fitbit doesn't
make exercise more fun. It just reminds me
how-- what a slob I am right now, doing nothing. So I think maybe that's-- If I were in the
tech industry, that's what I'd put my money into. That's what I'd spend my effort
on is trying to figure out ways to use technology
to help people enjoy themselves and make
things rewarding and happy to talk to anybody about that. PETE WILLIAMSON: OK. Let's move on to
the next question. We have time for
one or two more. OK. I'm not sure I can pronounce
your name correctly, but from Kweku Taylor-Hayford. When practicing
intermittent fasting, does meal timing have an effect? Is it better to skip breakfast
than dinner, for example? DAN LIEBERMAN: Yeah. Look, first of all, I'm an
expert on exercise and not on intermittent fasting. So I'm going to have
to pass on that one. I would say yeah. You'd have to--
There's a big review article in the New England
Journal of Medicine that just came out. I'm not sure there's a lot
of really good data on that. But yeah. I'm going to focus on exercise,
not intermittent fasting. But yeah. You'll have to ask the
question elsewhere. If you do intermittent fasting,
don't forget to also exercise. I don't think it's a substitute. Put it that way. Intermittent
fasting, for example, is not going to really
lower your blood pressure. PETE WILLIAMSON: OK. From Steve Stepanian. Is there a recommended
optimal amount of how much to balance
cardio and strength training? DAN LIEBERMAN: Well, one of
my chief arguments in the book is to stop thinking
about this word optimal when it comes to exercise. There is no such
thing as an optimal. It depends on who you
are, how old you are, whether you're male or
female, how fit you are, what your energy-- what your
injury background is like. Are you' worried
about health disease? Are you worried
about heart disease? Are you worried
about Alzheimer's? Are you worried about diabetes? Are you worried
about osteoporosis? Everybody's different. And for the most part, there's-- optimum, it seems that
there's like a curve. There's an increasing
benefit, and then there's a-- then there's a--
there's an increasing cost. But for most exercise,
there's no evidence for that. There's actually-- It's a
curve that goes like that, and it flattens out. And there's very little evidence
that actually too much exercise is bad for you. And almost nobody's at
those extremes anyway. So it doesn't really matter. So the answer is there is no-- there is no optimum. That said, a lot of
experts recommend if you're going to do a minimum-- I think you can say
there's a minimum-- is that you should, again, try to
get that 150 minutes a week. That's a good
reasonable minimum. And as you get older,
it's really important to try to incorporate
some strength training. And so the American
College of Sports Medicine, and the Surgeon
General, and others recommend that at
least twice a week you do some-- you do some weights. But there is no such
thing as an optimum. That's this part of
this medicalization of exercise, which I
think confuses people and gets people exercised. It's an evanescent,
quixotic notion. There is no such thing. PETE WILLIAMSON: OK. I think we have time
for one more question. So let's take the next question. So from Kevin Murphy. What was the most unexpected
or interesting finding while you were researching
the material for exercise? DAN LIEBERMAN: Oh, God. I don't know. There's so many bizarre
and interesting things. It's probably easier to say
what I thought other people have found most interesting. So here's one fact that seems
to blow people's mind, which is that the average
sedentary American is more active than a
typical wild chimpanzee. And this is research that's been
shown by various colleagues. I've been out and had a
chance to watch chimpanzees, and I can vouch for that. We are cousins. The animals that we evolved
from were couch potatoes. And that's actually
a very important part of the story of
exercise, because we evolved to turn up the dial
and become much more physically active. And that's built
into our physiology and built into our biology. And I think it's changed our-- us in very special ways. But there's so many other
bizarre and interesting facts. I'm not sure. That's a tough question. But I hope that the book is full
of interesting, and strange, and wonderful facts. But it's very hard for me to
bring one right to my neocortex at the moment. Sorry. PETE WILLIAMSON: All right. Well, thank you very
much, Dr. Lieberman. As a reminder, this is the book
Exercised that just came out. So it should be available
now at somewhere near you, either online or if you actually
can find a store that's open, perhaps the store. And I also want to say thank
you to all of us who are here with us on YouTube and asking
the questions during the show. And I hope you all enjoyed it
and got something out of it. Once again, thank you very much. DAN LIEBERMAN: Thank you. Thank you so much. [MUSIC PLAYING]
