A new study in mice points to how cell biology, not willpower, might be the root of yo-yo dieting.
The American conventional wisdom about weight loss is simple: A calorie deficit is all that’s required to drop excess pounds, and moderating future calorie consumption is all that’s required to maintain it. To the idea’s adherents, the infinite complexity of human biology acts as one big nutritional piggy bank. Anyone who gains too much weight or loses weight and gains it back has simply failed to balance the caloric checkbook, which can be corrected by forswearing fatty food or carbs.
Endocrinologists have known for decades that the science of weight is far more complicated than calorie deficits and energy expenditures. And in 2016, the fickle complexity of weight came to broad national attention. In a study of former contestants on a season of the weight-loss reality show The Biggest Loser, scientists found that years later, the contestants not only had gained back much or all of the weight they’d lost on the show, but also had far weaker metabolisms than most people their size. The contestants’ bodies had fought for years to regain the weight, contrary to the contestants’ efforts and wishes. No one was sure why.