Moment 206: Harvard Professor Reveals The Biggest Lies About Exercise & Weight Loss!

In the first chapter of your book, you say that you went to visit the Native American tribe, and I'm going to try and perhaps pronounce this, the Tarahumara.

Tarahumara.

And they're famous for their long running.

Yes.

What did you learn about running from them?

Well, you know, they have been famous for well over 100 years.

I mean, many people have gone to study the Tarahumara and have commented on their amazing ability to run.

But what I really learned from them is that for them, physical activity is spiritual. You know, there's this book, Born to Run, that describes their running and calls them a hidden tribe of super athletes.
They're not hidden, and they're not super athletes. And the one thing that the book missed was that the main impetus for the

running, these famous long distance races, is that it's a form of prayer. It's really very beautiful.
And it's a metaphor for life. And it's also an opportunity to bet in sports and all that.
but it's all wrapped into one.

And what I've learned was that this actually used to be almost universal among Native American populations, right? Native American tribes. Everybody had long-distance races and ballgames, and they all had a spiritual element.
It's just that they've retained their traditions because they're in a very remote part of Mexico that's essentially inaccessible. We all used to do this.
All humans used to do this. And in fact, if you look around the world, every population has this tradition of endurance events.
Some of the subject that you talk about in your book, but also outside of your book, is how we used to run in terms of, I was at the foot the foot doctor what's it called i don't know what they're called podiatrist that's what i said but podiatrist what did i say but i went to the podiatrist the other day because i i got this what's it called when you're gonna point out on my foot this part of my foot here started to get lots of pain every time. Plantar fasciitis.
That's it. Plantar fasciitis.
I started to get some plantar fasciitis. That's so fun.
And it was just this ongoing pain. And they prescribed me some insoles.
I stood on a couple of machines, some soft stuff. And they measured my foot and took this scan of it and said, right, basically, you're standing wrong.
Your arch is a bit too too flat take these insoles and wear them in all of your shoes and i just i always think in these moments when someone prescribes me something that's not natural i go why like where did i go wrong and i think that's the key question where did i go wrong who lied to me to the point now that at 30 old, I have these bloody insoles that I have to put in all my shoes. Because presumably, that's not natural.
Presumably, my ancestors don't have bloody insoles. Yeah.
So, plantar fasciitis is what I would call a mismatch disease, right? A disease that's more common or more severe because our bodies are inadequately adapted to modern environments. And in your case, and as is the case with a lot of people, you have a weak foot.
So we, you know, you look like you go to the gym. Looks like you're a pretty fit person, right? I'll make a bet you strengthen pretty much every muscle group in your body except your feet, right? No comment.
Right. Well, but we don't, right? And one of the reasons is because we encase our feet in stiff-soled shoes that are very comfortable.
And the reason the shoes are comfortable is that your foot muscles have to do less work when you're using those shoes, right? We have shoes that are stiff soles. They have arch supports, right? And your foot has four layers of muscles in them.
And those muscles are supporting your arch. And at the bottom of those four layers of muscles is this layer of connective tissue, the plantar fascia.
And the problem with the plantar fascia is that if it stretches too much, it, like anything else, right, it gets inflamed. But it's got almost no vascularization, right? So it's very hard for it to repair itself when it gets inflamed.
To prevent plantar fasciitis, the best way to preventing it is having a strong foot. A strong foot's a healthy foot.
So the way to treat the disease on the long term is to strengthen your foot. But if you want to just alleviate the symptoms, that's what your podiatrist did.
By giving you an insole, right, it's basically preventing your arch from collapsing as much, making it more comfortable so your plantar fascia gets stress less, and so it can kind of alleviate that stretching and hence the pain, right? So that's a typical example of what I call disevolution. It's what happens when you treat the symptoms of a mismatched disease rather than their causes or preventing their causes.
So podiatrists are a bit like drug pushers in that sense, right?

Because they're essentially putting your foot in a cast, right?

And for the rest of your life, you kind of have to keep using them

unless you strengthen your feet.

So there's nothing wrong with those, you know, treating the symptoms.

I mean, pain is no fun.

So where are the insoles, right, to kind of, you know, alleviate the pain?

But also work on strengthening your foot.

And I think you'll find that the plantar fasciitis will disappear

and never come back.

So the plantar fasciitis has now healed

after about a month of wearing the insole.

I no longer have the insoles with me here in New York,

and I don't have them in any of my shoes because I've also taken a bit of time off running on my feet. I was playing a lot of football.
So now I'm at a point where I can go to the preventable stage, prevent it happening again. And you said to strengthen my foot.
How does one strengthen their foot? Good question. So there are some exercises.
They're kind of foot doming exercises and things like that. I can send you some links to videos showing you some good foot strengthening exercises.
So that's one way to do it. But the other way is to wear more minimal shoes, to wear shoes that aren't stiff-soled, that don't have arch supports.
Go barefoot a lot, right? And that will naturally strengthen the muscles in your foot because you'll have to use those muscles. So you ever gone for like a long walk or run on a beach, right? And afterwards, your feet are kind of tired, right? The reason your feet are tired is because you're now walking on a compliant surface, right? It's not stiff.
So your muscles are having to work more to stiffen your foot to push you forward, right? Jack, could you go grab the black shoe out of my bag? I just want to show him something. So wearing shoes that aren't as stiff-soled, they don't have arch supports, will slowly strengthen your feet.
But, and this is a huge but, if you do too much too fast, your plantar fascia will come roaring back and you'll hate me. You'll never forgive me because, yeah, those are Vivo Barefoots.
Yeah, I wear the same shoes. Oh, you've got the same shoes on.
Great shoes. Yeah, those are wonderful shoes.
Those are exactly the kind of shoes that will help strengthen your feet. These are fairly a new addition in my life.
Yeah. And they feel really strange because you can kind of feel the floor.
Yeah. It's exactly what you've described.
But you can transition. If you have weak feet, which I'm guessing you do, if you suddenly, if that's the only shoe you wear all the time, you'll probably regret it, right? So, so slowly, slowly, slowly increase the percentage of time that just like anything else, if you, if you like suddenly decide to lift, you know, huge weights that you can't lift before, you'll hurt yourself, right? The same thing is with your feet.
So, so slowly it does it, but you, if you do it gradually and slowly and carefully, you can build up strength in your foot and you'll be a happier person.

And this goes back to everything else you've said about how choosing comfort, choosing to have a nice supportive shoe has actually just kind of deferred a problem off into the future for me.

It's the same with diet.

It's the same with avoiding exercise and being sedentary and all these other things, where when you choose the easy road in the short term,

which is this wonderful cushioned shoe I've chosen,

the muscle hasn't built up in my foot and I've paid the price.

Correct.

So I need to, again, choose discomfort more in the short term,

go up the stairs, run barefoot to avoid the consequences later down the line.

Yeah.

I mean, I don't think you have to run barefoot, though it can be fun, but yeah. I mean, and I can think of plenty of other examples.
We love comfort, but comfort's not necessarily good for us. There's another myth that you bust, which I thought was really interesting, because I think I know a lot of people that have used this as a reason not to run.
They say, it's really bad for your knees. Oh man, that gets me so mad, right? I mean, I hear this from doctors all the time, right? Oh yeah, running is bad for your knees.
Now it is true that knee injuries are the most common running injuries. But arthritis, which is really what they're usually talking about, it's absolutely definitively not true that running increases rates of knee cartilage damage and arthritis.

So arthritis is caused by cartilage wearing away in a joint, right? And it's a myth that running actually increases cartilage damage. If you have arthritis, running is excruciating and problematic.
But if you don't have it, running actually, if anything, may be slightly preventive because cartilage joints, like everything else, benefits from being used, right?

And so physical activity actually helps promote strong and healthy joints. We used to think that it just caused them to wear away, but actually, you know, like cars, you know, wearing away at their tires.
But now we know that actually physical activity promotes repair mechanisms in cartilage just as it does in other tissues in the body. And, of course, the other thing about running is that I think a lot of people run incorrectly today.
So that's why we started studying barefoot running a few decades ago, is because if humans had been running for millions of years, most of that time we were running barefoot. So we're kind of curious, how did people run before shoes? And what we learned was that today shoes have these cushioned heels that enable you to essentially run the way you walk, right? You land on your heel.
And everybody who's barefoot sometimes lands on their heel, but people who are barefoot often, more often than not, land on the ball of their foot and then let their heel down. It's called a forefoot strike or a midfoot strike.
And when you do that, we worked out the biomechanics of that and published a paper on the cover of Nature, showing that when you do that, you actually prevent your foot from crashing into the ground, causing what's called an impact peak, a collisional force. You run lightly and gently.
So if you were to take your shoes off and run up Lexington Avenue here, I guarantee you, you would not be landing on your heels. Within a few steps, you'd start landing on the ball of your foot because it hurts less.
And so that's how we evolved to run. We evolved to run in a way that doesn't involve slamming into the ground with every step.
And that causes less forests around your knee. The trade-off, though, because nothing comes for free, everything has trade-offs, is that it's harder on your ankles.
Your calf muscles and your Achilles have to do now a lot more work to let your heel down. And so people who switch from heel striking to forefoot striking often have Achilles tendon problems.
They get calf muscle problems. If they don't do it properly, they'll get, if their foot muscles aren't strong enough, they'll get all kinds of foot problems, right? So you can't just suddenly become a barefoot runner and start forefoot striking.
If you're going to switch, you have to switch gradually and slowly and build up strength and learn to do it properly. Another thing people do is they tend to run like a ballerina high up on their toes.
That's really hard on your ankles and your calves. So you've got to do it properly, but it can have enormous benefits.
And we know, again, if you run that way, it puts much less force on your knees. And again, knees are where people get injured the most.
So I think a lot of knee injuries come from the way in which we run. So would you recommend, if you can, to run more barefoot? Especially if you have those kind of shoes we just discussed.
Well, I think what matters is how you run, not what's on your feet. So I would say a barefoot style.
How do I learn to run in a new way, though? Well, I mean, there's some tricks. So one of them is, first of all, I don't know how you run.
So maybe you already run just fine. But a barefoot style tends to be a high stride rate or high stride frequency.
So 90 strides per minute or 180 steps per minute, roughly. You know, 170 to 180 steps per minute is about right.
Relatively short strides, so you're not throwing your leg out. And to me, the most important thing is not what we call overstriding.
If you ask any coach on the planet, they'll say overstriding is bad. Overstriding is when you throw your leg out way in front of you and you land.
And that leg is a stiff leg. So a stiff leg means more force, right? And it's harder on your knees.
And so a good runner lands with their shank, with their tibia vertical. So their ankle is below their knee.
When you do that, pretty much everything will work out properly, right? It'll mean that you won't land hard on your heel. It'll mean that your leg will be acting like an excellent spring you won't produce a lot of breaking force um it's a it's a it's to me i think the most important skill in running is not to overstride um and um so i actually tell me so don't worry about how you're going to hit the ground just worry about your overstride if you solve your over overstride, you're more likely to run well.

What do you think some,

what's the best kind of sort of cardiovascular exercise for the promotion of good health?

Because I've been doing some CrossFit stuff.

I've been doing some HIIT workouts.

I've been trying not to run

because I've had a few injuries.

I'm trying not to run as much

because it seems to be a little bit more impact

than if I'm bullshitting myself there.

So I've been doing some like HIIT workouts for 30 minutes a day when I leave here. Well, you do hit works every single day.
Pretty much every day at the moment. We track it with a group of friends we have.
There's 10 of us in a WhatsApp group. Whoever's last, whoever does the least workouts every month is evicted.
And there's a raffle. So there's a raffle yesterday on the first, was it the first yesterday? Yeah, for for a new member and we do that every month and we've done it for three and a half years that's great i've been in there i was the first ever member so i've been in there for three and a half years well i think you know i mean the most the best exercise the one you like doing but is there one that's like better you know like the you know i think you got to mix it up there is no one right? I mean, I think what you do sounds actually pretty good, right? You've got a mixture of low, slow intensity, some high intensity.
You want to have some strength training. You want to have some cardio.
I mean, we never evolve to do one thing, and our bodies are too complex to benefit from just one thing. mixing it up is the obvious way to go, right? I think the bedrock for any kind of physical,

I mean, you've asked anybody, right? Cardio is the bedrock of exercise, right? It promotes the most health benefits, right? It's good for your burning energy. It's good for your cardiovascular system.
It's good for controlling inflammation. But there are different kinds of cardio, high intensity versus low intensity.
And there's also strength training, right, which is also important. So, you know, there's no – look, we've tried to medicalize exercise, right? It's like there's a proper dose, right? You know, take this pill this many milligrams this many times per week, right? Exercise, it doesn't work that way.
There is no optimal dose. Everybody's different.
It depends on are you more worried about heart disease or Alzheimer's or diabetes or depression or are you previously injured? Are you fit? Are you unfit? It's impossible to prescribe exercise in this kind of medicalized way. It doesn't work.
A lot of people exercise because they believe it will help them to lose fat, belly fat. One of the biggest debates on the planet.
It has been a huge debate. Even on this podcast, I've had multiple people come and say a whole range of things about weight loss and cardio.
And I'm kind of, I don't know what to believe anymore. Well anymore well anybody wasn't confused doesn't understand what's going on right you know it's um it's sad that there's such a debate um but um but that's how science works right so um as you know i wrote about that in this book um Part of the explanation for the debate is that, again, what dose are you analyzing and what population, in what kind of context, right? So pretty much every major health organization in the world recommends that you get 150 minutes per week of physical activity.
That's kind of like the benchmark. That's what the WHO, the World Health Organization, considers the division between being sedentary versus active.
And a lot of people who are unfit and overweight and struggling to be physically active have struggled to get 150 minutes a week, right? So a lot of studies prescribe 150 minutes a week of exercise, walking, for example, a moderate intensity physical activity, and then look at its effects on weight loss. And guess what? When you walk 150 minutes a week, which is what, 20 minutes a day of walking, which is about a mile, a mile a day, you're not going to lose much weight.
You're basically burning about 50 calories a day doing that, right? That's a piddling amount of calories compared to drinking a glass of orange juice, right? So surprise, surprise, those kinds of studies show that those doses of physical activity are not very effective for weight loss. However, plenty of rigorous controlled studies that look at higher doses of physical activity, 300 minutes a week or more, find that they are effective for helping people lose weight, but not fast and not large quantities.
So you're never going to lose a lot of weight really fast by exercising. It's just not going to happen.
Because a cheeseburger has what, 800, 900 calories. You have to run 15 kilometers to burn the same number of that, to burn the same number of calories.
You're going to be hungry afterwards too. So you're going to make some of that back.
You have compensation. So physical activity is actually, there's just no way around it.
You have to be a flat earther not to argue this way, but physical activity can help you lose weight, but it's not going to help you lose a lot of weight fast and not at the low doses that often are prescribed. But the one thing that we do agree on, and I think this would not be controversial, is that physical activity is really important for helping people prevent themselves from gaining weight or after a diet from regaining weight.
And there are many, many studies which show this. One of my favorite was a study that was done in Boston on policemen.
You know, policemen kind of have a reputation for, you know, having too many donuts and being overweight, right? And Boston is no exception. So they did this great study at Boston University, right across the river, where they got a bunch of policemen on a diet, a really severe diet.
The policemen all lost weight. But some of the policemen had to diet and exercise, some just dieted alone.
And as you might imagine, the ones who dieted plus exercise lost a little bit more weight, not a lot, just a little. And then they tracked them for months afterwards, because most people after a diet, the weight comes just crashing back, right? The policemen who's kept exercising, even after the diet was over and they went back to eating whatever the hell they wanted, donuts, whatever, they're the ones who kept the weight off.
But the ones who didn't exercise, the weight came crashing back. Another good example would be, have you ever seen the TV show The Biggest Loser? Yes, where people go on and lose weight.
Yeah, so there's a crazy show, right? These people, you know, this is like totally unhealthy. They were confined to a ranch in Malibu and these guys, these people lost ridiculous amounts of weight.
Guy named Kevin Hall at the National Institute of Health studied them for, for, for years afterwards and looked at, and most of them regained a lot of the weight that they lost. And there was one person on the show who did not.
And that was the person who kept exercising. Right.
And that's, you know, just yet more, one data point. But there's lots and lots of evidence to show that physical activity, what its other important benefit when it comes to weight is preventing weight gain or weight regain.
When we talk about dieting, we talk about exercise or diet, exercise or diet. Like, why is it an or? I mean, why isn't it exercise and diet? Diet is, of course, the bedrock for weight loss.
but exercise also plays an important role and should be part of the mix. On the police example and the biggest loser example, I can relate in the sense that when I exercise, when I go through the moments of my life where I'm most committed to exercise, I'm also most committed to my diet.
Yeah. Because if i go to the gym i will not then leave the gym and have a donut or a pizza absolutely not it seems like wasting the effort so if you look at the sort of correlation between the moments in my life where i eat healthiest they're also the moments in my life where i'm most most focused on the gym and i noticed there was a couple of months ago had a bit of slump, managed to stay in our little WhatsApp group, but coasted down the bottom of the leaderboard for a couple of months on end, just like surviving every month by one.
And through those moments, my motivation in the gym had gone down and my diet had gone down. The minute I managed to get in the gym and do a big workout, the same day my diet came back.
Yeah, of course. Right.
And they co-vary. Right.
And, and that's one of the reasons why when people do big studies of, of, you know, what, you know, you can look at what, what, what people die of, right. What's on the death certificate, you know, cancer, heart disease, whatever, heart attack.
And then you look at what caused the cancer, what caused the heart disease. When people try to do that, it's almost impossible to separate diet and exercise because people who tend to eat better also tend to exercise more.
They're both, in our modern upside down chopsy turvy world, they're both markers of privilege. People have money to go to the gym, also have money to buy healthy foods.
And people who care about their physical activity also tend to care about their diet. So at that level, they're very hard to separate.
However, if you're studying a particular component of a system in a randomized controls trial in a lab, you can separate them out. And so we know that they have independent and also interactive effects.
What is the most important thing we haven't talked about, Daniel? I think the most important thing is that we need to be compassionate towards each other. I mean, there's so much shaming and blaming and prescriptions and, you know, you know.
The reason I entitled the book Exercised is that people, we make people feel exercised about exercise. We make them feel uncomfortable and unconfident and shamed.
And, you know, you and I are having this conversation, but I can tell that you take, you know, you're, I mean, I know I've listened to enough of your podcast. You care about your health and you care about diet.
You care about exercise.

And people may look at you and think, gosh, I wish I was like him, but it's just not me. You know, I can't, I'm not, I'm not there.
Right. And they may feel put off by our conversation.
And I think that so often these discussions make people feel bad about what they're doing. And I think that what we need to emphasize is that if you put a chocolate cake and an apple in front of me here, I would want to eat the chocolate cake.
And I might eat the apple only because you're there. But if you weren't there, I would eat the chocolate cake, right? And when I'm in my building at Harvard, my office is on the fifth floor of this old Victorian building.
Every single day, I want to take the elevator. And the only reason I take the stairs is that if anybody catches me in the elevator, I'll be a hypocrite.
It's not that I don't want to take the elevator. I do want to take the elevator, right? I guess you guys say lift, right? And we make people feel bad for taking the elevator, right? They shouldn't feel bad.
It's an instinct. And so I think we have to figure out ways to help people without shaming them and without blaming them and without bragging

and whatever, talking about the marathon they ran or this, that, or the other, make them feel

less uncomfortable about the topic and realize that you don't have to swim the English Channel

or run a marathon or join your WhatsApp group and do crazy HIIT workouts every day. By the way, you don't need to do HIIT workouts every day to get the benefit.
Instead, just taking the stairs in your building every day. Anything is better than nothing, and you'll get benefits from that.
And I hope that that's the message that needs to get out, right? Anything is better than nothing. And if you can get started on that pathway, then it'll eventually become self-rewarding.
And that leads me to the other topic that we didn't talk about, which is that the reward system of physical activity. You know, you and I, if we go for, like, I'm really looking forward to my run tomorrow morning in the park.
I love running Central Park. It's one of the best places in the world to run, right? A fantastic view from the top, and it's just gorgeous, right? But when I run Central Park tomorrow, I'm going to get a big dopamine hit.
My body is going to produce all this dopamine, which is the molecule that says, do that again, right? It's a reward. Gamblers get dopamine hits, right? People eat chocolate cake, get a dopamine hit, right? But if I were unfit and overweight, I wouldn't get that dopamine hit.
And so when people start exercising, they don't get the reward that people who are fit and accustomed to doing it get. And then they're made to feel bad, like you didn't enjoy your run around Central Park.
Well, it takes months, if not years, before you actually get that reward. Really? Yeah.
Because just like being overweight causes you to become insensitive to insulin, you become insensitive to all kinds of other hormones and neurotransmitters, and dopamine is one of them. So it's not an instant benefit, right? It's hard.
And so we need to be compassionate again towards people who are struggling to become fit and struggling to get the reward. And also, if you're overweight and you run around Central Park, it's like if I were carrying weights and running around Central Park, it'd be much harder, right? It's challenging.
And so once you get into that state, it's hard to get back to the state of activity. And so we need, as a society, to help those folks rather than judge them.