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The Real Reason it's Hard to Lose Weight

Updated: Mar 16, 2021

Exercise is vitally important for your health - it just won’t make you thin - discovers a leading metabolism scientist, after a startling realisation while living with an African tribe.

When Herman Pontzer set off for the wilds of Tanzania to spend a summer with the local Hadza people, he thought he knew what he would find. As an evolutionary biologist, his aim was to measure how the Hadza’s hunter-gatherer lifestyle causes them to burn more energy. Because we all know the more exercise you do, the more calories you burn and the slimmer you become, right? Actually no, not exactly.

What Pontzer and his fellow researchers discovered flew in the face of received wisdom about how our metabolism works. Although the Hadza lead far more active lives than ours - routinely walking long distances, they undertake more physical activity daily than most of the rest of us do in (at least) a week - their energy expenditure was no greater. They were burning the same number of calories as men and women from industrialised populations. Our bodies, concluded Pontzer, seem to maintain daily energy expenditure within a narrow band, no matter what lifestyle we lead. So while obesity is largely caused by overconsumption, it appears there’s little we can do to change the calories we burn.

As Pontzer writes in his new book, Burn: The Misunderstood Science of Metabolism: “We have [got] the science of energy expenditure fundamentally wrong.” His conclusion? Cut calories to lose weight. But still keep exercising.

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