It is generally recognized that exercise is healthy. But it is not true that you also lose weight from exercise. This is evident from an American study into our metabolism.
Walking, cycling, jogging: for many of us the successive lockdowns have been an excellent opportunity to exercise more. A study by the University of Antwerp in June showed that 30 to 50 percent of Flemish people exercise and exercise more than before the corona crisis.
But if we are to believe the evolutionary anthropologist Herman Pontzer, most of us do not lose body weight. In his new book Burn, which will be released next month, he argues that no less than 2 million years of evolution are playing to our disadvantage.
Pontzer is a professor at Duke University in North Carolina, USA, who has spent the past decade studying a tribe of hunter-gatherers from Tanzania: the Hadza. Using urine tests, he was able to calculate how much carbon dioxide the hunters produce, from which he could deduce their energy consumption.
The average adult Hadza man travels about 9 miles every day to hunt and forage for food. Heavy work, compared to our sedentary behavior. And yet, Pontzer discovered, their energy expenditure in relation to their body weight is almost as high as ours. Our evolved metabolism would be in between.
Sixty percent of our calories are used in the resting metabolism, the amount of energy that our body burns in a resting state. The cells in our muscles and organs, and especially our brains, need all this energy to perform our daily tasks. In addition, our body maintains the immune system, hormones must be produced and our body heat must be maintained.
According to Pontzer, our body, more specifically the hypothalamus in the brain, therefore has a target value for its energy expenditure. When we exercise, we simply reduce the amount of energy we use for all of the other things – to maintain balance.
For example, our immune system suppresses the inflammatory and stress responses, so that we get less stress. The production of the sex hormones is also slowed down: Hadza men have half the testosterone level of men in the industrialized world.
It has been known for some time that you lose surprisingly little weight with exercise. But Pontzer takes this a step further: he says in his new book that it does not change our daily energy consumption at all.
Still, you don’t have to immediately put away your running shoes. Pontzer also emphasizes that we are made to walk. By exercising, we not only live longer, but we also become healthier and happier.