The Economist. This week we'll be talking about the human body, in particular how the body uses energy.

I'm going to be speaking with a researcher who I've been fascinated by for a very long time.

To explain why, I'll need to take you back to my childhood.

Now, I was a pretty healthy but also pretty chubby kid, and for as long as I've had control

over what I eat, I'm talking about after leaving home here, I've been hyper aware of ways to

keep my weight and various edible temptations at bay.

So I followed various fad diets over time, including at one point the original

low-carb Atkins diet. And I've also spent a lot of time in gyms. On exercise bikes, cross-trainer's,

I even tried out a spin class once and ended up vomiting straight

afterwards. Never doing that again. Sometimes these diet and fitness regimes worked, but mostly

they didn't, because they were so hard to stick to. I did plow on though because through years

as a science and health writer and speaking to

many, many scientists, I had learned that to stay healthy involved watching what you eat

and also making sure to move around a lot more. That was the science that had been ingrained into me.

The only thing that mattered if you wanted to maintain healthy weight

was calories in versus calories out. Aerobic exercise, running, cycling, swimming,

these were the best ways to increase the second half of that equation. Then I came across Herman Pzer's work, and it kind of blew my knowledge of human metabolism apart.

His research is all about understanding how and why human bodies use energy in the way that they do.

He'd spent several years living with and studying the Hadza people, a hunter-gatherer community

in Tanzania.

And through them, he'd discovered something remarkable.

To our shock, it was really indistinguishable the number of calories being burned if you're

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