Anyone who has ever successfully lost weight knows how hard it is to keep it off, but a new study published today in the journal Obesity shows that your metabolism—not willpower—may be to blame. It turns out once you lose weight, your body tries to hold onto calories tighter than your hold on that skull tank at the SoulCycle sample sale.
Kevin Hall, a scientist at the National Institutes of Health, followed the season 8 contestants of The Biggest Loser over the past six years, tracking their weight loss and—inevitably—weight gain. While most were more active and kept a healthier diet to improve their overall health, all but one gained almost all of the weight back—and a few even gained extra pounds.
“When the show began, the contestants, though hugely overweight, had normal metabolisms for their size, meaning they were burning a normal number of calories for people of their weight,” the New York Times reports. “When it ended, their metabolisms had slowed radically and their bodies were not burning enough calories to maintain their thinner sizes.” While most metabolism levels slow down when any sort of restriction is in place—i.e. why you should never skip breakfast—what shocked the researchers was that their metabolism never returned to a normal level, and instead got even slower over the years.
Basically, their metabolism was their frenemy—secretly sabotaging them from keeping the weight off.
Researchers also found that the ex-contestants had almost non-existent levels of leptin—the hormone that controls hunger (as leptin goes down, hunger goes up). Despite a strict diet and increased levels of exercise, the contestants felt extreme levels of hunger, making weight maintenance nearly impossible, let alone any weight loss. Talk about fighting a losing battle.
“The difficulty in keeping weight off reflects biology, not a pathological lack of willpower,” Michael Rosenbaum, MD, an obesity researcher at Columbia University, told the Times.
Researchers are working on a hormone replacement that would act like leptin in the body and help curb hunger in a healthy way and naturally rev up your metabolism, but in the meantime experts say the back-and-forth of super-restrictive diets and the weight gain is, ahem, a losing proposition.