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

**Steven Bartlett** (0:00)
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.

**Daniel Lieberman** (0:07)
Tarahumara.

**Steven Bartlett** (0:08)
And they're famous for their long running.

**Daniel Lieberman** (0:11)
Yes.

**Steven Bartlett** (0:11)
What did you learn about running from them?

**Daniel Lieberman** (0:13)
Well, 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, they do 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. 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 ball games and they were 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 think, if you look around the world, every population has this tradition of endurance events.

**Steven Bartlett** (1:38)
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, you know, I was at the foot doctor. What's it called? I don't know what they're called.

**Daniel Lieberman** (1:49)
The podiatrist.

**Steven Bartlett** (1:50)
That's what I said. The podiatrist. What did I say? But I went to the podiatrist the other day because I got this, what's it called? When you're, I'm gonna point it on my foot. This part of my foot here started to get lots of pain.

**Daniel Lieberman** (2:05)
Plantarificitis.

**Steven Bartlett** (2:06)
That's it. Plantarificitis. I started to get some plantarificitis.

**Daniel Lieberman** (2:09)
That's so fun.

**Steven Bartlett** (2:10)
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 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 years 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.

**Daniel Lieberman** (2:53)
Yeah.
So plantar fasciitis is what I would call a mismatched 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 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 muscles group in your body except your feet, right?

**Steven Bartlett** (3:21)
No comment.

**Daniel Lieberman** (3:22)
Right. Well, but we don't. 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 prevent it is having a strong foot. A strong foot is 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 stressless, 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 the cast, right? And for the rest of your life, you kind of have to keep using them unless you strengthen your feet.