There are many reasons to exercise more. Regular exercise strengthens the cardiovascular system and keeps the immune system fit. Muscles and joints are strengthened, which reduces the risk of injury. After a strenuous workout you feel better, stress is reduced and blood circulation is stimulated. However, according to evolutionary biologist Herman Pontzer, losing weight is not one of the reasons for more exercise.

Pontzer is considered a recognized expert on human metabolism and has published an English-language reference book on the subject, "Burn: New Research Blows the Lid Off - How We Really Burn Calories, Lose Weight, and Stay Healthy". In it he disputes the widespread thesis that more exercise leads to higher calorie consumption and thus greater weight loss.

"Your brain is very, very, very good at matching how many calories you're eating and how many calories you're burning," Pontzer said. "The person who leads a sedentary lifestyle will burn the same number of calories as a person who leads an active lifestyle."

This statement may seem like a paradigm shift. But the human metabolism works differently than most people assume. Anyone who significantly increases their activity level - be it through rowing, jogging or excessive strength training - will also burn more calories in the first few months. But this effect diminishes over time. According to Pontzer, the body begins to use less energy for its other tasks. After a few months, the pre-training level was basically reached again.

Pontzer bases his thesis on the knowledge he gained while studying the Hadza people in Tanzania. This is an ethnic group of around a thousand people who live scattered around the shores of Lake Eyasi in East Africa. They are considered hunters and gatherers and thus one of the last communities living close to nature, which still partially uses stone tools.

The Hadza have to walk miles every day to get food. They lead significantly more active lifestyles than most people in western cultures. Pontzer and his colleagues were all the more surprised when they determined the calorie consumption of the Hadza using scientific methods: the amount was almost identical to the consumption of Western city dwellers, who lead a comparatively sedentary everyday life.

For Pontzer, it was clear: the human metabolism is constantly adapting and making room for increased activity, so that daily energy consumption ultimately remains within a narrow corridor - completely independent of the actual lifestyle.

In order to shed excess kilos, you shouldn't force yourself to do an extra jog, says Pontzer, but simply eat less. "We've known for decades that exercise is a really bad way to lose weight," he says. "The only strategy that seems to work really well is to focus on diet."

In the professional world, however, not everyone fully agrees with this thesis. Deborah Riebe, a professor of exercise science, told Today that a combination of exercise and diet leads to 20 percent greater weight loss than diet alone. Sport as a supplement to a more conscious diet is therefore beneficial and, above all, prevents weight gain again.

In his book, however, Pontzer also deals extensively with the topic of nutrition and its influence on human metabolism. So he admits another myth: foods like cayenne pepper, chilli powder and green tea are said to boost metabolism. However, this effect is so infinitesimally small that a single additional bite of food essentially negates it. "If you boost your metabolism a little bit, your brain will say, 'Oh OK, we'd better eat a little more' and you wouldn't lose anything at all."

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