weighty matters

Why Do So Many Dieters Gain Lost Weight Back?

Biggest Loser season 8 contestants Danny Cahill, Dina Mercado, and Sean Algaier.
Biggest Loser season 8 contestants Danny Cahill, Dina Mercado, and Sean Algaier. Photo: Trae Patton/NBC/NBCU Photo Bank via Getty Images

Anyone who’s lost weight knows that it can be hard to keep it off. A new study involving former The Biggest Loser contestants, who shed weight quickly and publicly, is a reminder of a key characteristic of metabolism: If your body thinks it’s starving, it will hold on to calories as tightly as you hold on to the last pair of sample-sale Louboutins in your size.

Kevin Hall, a researcher at the National Institutes of Health, followed 14 contestants from season eight for six years. In a new study in the journal Obesity, he reports that all but one of them weigh more than when the show ended in 2009, and four people are even heavier than they were during the premiere.

At the start of season eight, each one of the contestants had a normal resting metabolism (or basal metabolic rate, BMR) for a person of their size. When the show was over, their metabolisms had slowed dramatically, enough that they couldn’t maintain their new weight. This finding wasn’t surprising because it happens to literally anyone who diets and, on a smaller scale, when people skip breakfast — with fewer calories present, your body automatically conserves energy. But the researchers were shocked when, after six years, the contestants’ metabolic rates didn’t recover. They slowed even more.

One example: Season-eight winner Danny Cahill weighs 295 pounds now, versus 191 during the season’s finale, and he has to eat 800 fewer calories per day than another man his size just to maintain his weight. Other contestants saw their BMRs fall by 200 to 600 calories. Even Erinn Egbert, the only person who weighs less now than on the day of the finale, burns 552 fewer calories per day than a typical woman her size.

The contestants also had lower levels of the hunger-controlling hormone leptin. Leptin decreases after weight loss, increasing hunger as part of a physiological response to return to your pre-diet weight. Their leptin levels were normal before the show, but afterward they had almost none of it  — they would have been ravenous. As they gained weight, the leptin did start to come back, but only to about half the level it was before.

It’s not the first time researchers have studied Biggest Loser contestants. A 2012 study, on which Hall was a co-author, suggested that being on the show damages metabolism as contestants’ metabolic rates slowed more than what would usually happen when a person loses weight. They speculated that alums would need to keep up the intense exercise and calorie restriction in order to keep the pounds off. This new paper suggests that theory is true, and that it isn’t even the whole picture when you consider hunger hormones.

It’s a very small study involving people on a controversial show who did extremely intense exercise in the face of calorie restriction, but it has some useful (if sad) lessons for people who won’t head to a ranch to drop over 100 pounds in six months, or even have 100 pounds to lose. The first is that your brain doesn’t like it when you lose weight, even if it’s healthier for you, because your brain is more focused on short-term survival. Also, losing weight unfortunately means feeling more hunger, which helps no one. Medical experts are working on that in face of the obesity crisis.

As Australian researcher, Joseph Proietto, who was not involved in the study, told the New York Times: “The body puts multiple mechanisms in place to get you back to your weight. The only way to maintain weight loss is to be hungry all the time. We desperately need agents that will suppress hunger and that are safe with long-term use.”

Why Do So Many Dieters Gain Weight Back?