Medicosnext
In his book, Burn: The Misunderstood Science of Metabolism, evolutionary biologist Herman Pontzer writes about the misunderstood science of metabolism based on his time living with the Hadza tribe in Tanzania. His objective was to measure the amount of energy burned by the Hadza people, who follow a hunter-gatherer lifestyle, one that is very active. Pontzer discovered that the common notion of more exercise burning more calories, thus leading to a slimmer you, isn’t entirely true.
He found that while the Hazda people had a very active lifestyle, with walking long distances a daily routine, they did not spend a greater amount of energy than the average American did in a week. In fact, Pontzer was surprised to find that the amount of calories burned was equal to the amount burned by people in industrialized populations. This led him to conclude that, irrespective of the lifestyle, our bodies appear to maintain daily energy expenditure within set limits. This means that although obesity is mostly due to overeating, there’s not much that can be done to change the amount of calories we burn. This new understanding of metabolism, which is supported by a number of studies, has great implications on how the growing obesity epidemic in rich countries, such as the US and UK, are tackled.
Pontzer believes that it’s hard to measure metabolism, because there were no scientific techniques to do so till now. As an example, he writes that a typical 150 lb adult, who religiously walks 10,000 steps daily, will burn about 250 kcal, which equals to eating half a Big Mac hamburger. Similarly, climbing one flight of stairs burns only about 3.5 kcal, which is much lesser than consuming a single M&M chocolate. He states that while exercise won’t make you thinner, it is very essential for your health. He writes, “If you start a new exercise program tomorrow and stick to it religiously, you will most likely weigh nearly the same in two years as you do right now.” Nevertheless, he also adds, “You should still do it! You’ll be happier, healthier, and live longer. Just don’t expect any meaningful weight change in the long term from exercise alone.”
According to him, ultra-processed and highly flavored food, which is so common in Western diets, is the real villain, unlike the plain diet of whole foods that the Hazda people eat, which keeps them slimmer. He writes, “All the research we’ve done in the last 10 years—not just my lab but other people, too—points to diet as being the culprit here for obesity. It’s not sloth, it’s the food.” Apparently, people tend to eats more quantities of unhealthy food because they provide less nourishment per se. External factors like stress also influence our eating habits—comfort-eating and stress-eating being real facts—so, reducing emotional and psychological stress, along with physical stress due to sleep deprivation, may help in controlling the tendency to overeat.
Thus, obesity being the result of complex interplay of biological and socio-economic factors, once we become overweight or obese, our highly evolved metabolism makes it very difficult to lose the extra weight. Pontzer believes that the primary reason why the Hadza people stay thin is because they eat a diet that doesn’t have processed foods. Regarding the different types of diet that people follow to lose weight, he writes, “Every diet that works works because it cuts calories. There are different ways to do that. There’s no magic. Every diet works if you stick to it.” He says that the best diet for you depends on “your particular reward system and the variety of foods that satisfy you most on the fewest calories”.
