Exercise won’t solve the obesity crisis

With obesity levels at crisis point, governments all over the world are desperate to get their populations active; but according to a growing body of research, we can run around as much as we like, but it won’t solve the problem. In 2019, a team of researchers from Baylor University in Texas studied children living in the rainforests of Ecuador. They found that these children, who spent hours each day playing and foraging, were far more active than indigenous children in a nearby town, and significantly leaner, too. No surprise there. But when they studied how many calories the children burned each day, they found no difference between the two groups. This study built on earlier research by the evolutionary anthropologist Herman Pontzer, who’d studied Hadza huntergatherers in Tanzania, and found that, despite their intensely active lives, they burned no more calories than Westerners. His conclusion – as he explains in a new book called Burn

– was that humans have evolved a way of reallocating the body’s energy usage. So if we use calories by running, the body makes up for it by expending less energy on one of the many biological processes that burn calories – such as the immune system. That being the case, we have to assume it is not sloth that is making us fat, he says, but food. Too much of what we eat in industrial societies has been engineered to be tasty and hard to resist. And we eat too much of it. He is not advocating against exercise; on the contrary, he recommends it. “You’ll be happier, healthier and live longer. Just don’t expect any meaningful weight change in the long term from exercise alone.”