“My own history of yo-yo dieting started when I was 15 and lasted about three decades,” said Sandra Aamodt, a neuroscientist and the author of Why Diets Make Us Fat, on Saturday at Spotlight Health, a conference co-hosted by the Aspen Institute and The Atlantic. “I lost the same 15 pounds pretty much every year during that same period, and gained it back regular as clockwork.”
This is a classic tale—the diet that doesn’t take, the weight loss that comes right back. The most recent, extreme, highly publicized case was that of the study done on contestants from the reality show The Biggest Loser, most of whom, six years after losing 100 to 200 pounds, had gained most of it back, and had significantly slowed metabolisms.
The study provided a dramatic example of how the body fights against weight loss. And sheer force of will is rarely sufficient to fight back.
“Why is that we can’t just control our body weight?” Aamodt asked. “We all sort of think we can. You can decide whether to take that next bite of breakfast right? Why can’t we just keep that going over years? The answer is that your brain, like a number of poorly run institutions, is governed by committee.”
Some of those committee members are the brain’s reward system, which tends to find a cookie to be a better reward than a carrot stick, and the hypothalamus, which regulates what Aamodt calls the body’s “weight thermostat.” This thermostat prefers the body to be at a certain weight, called its “set point,” and if weight dips below or rises above, hunger and calorie expenditure are adjusted to try to bring it back. These systems are constantly active, Aamodt said.