One of the biggest frustrations for dieters is that it often seems more difficult to keep the weight off than lose it in the first place. That leads to weight that yo-yos and a sense of failure and shame for not being able to maintain the weight loss. This conundrum led one researcher to propose a study looking at why the contestants on the show "The Biggest Loser," who lose upwards of 100 pounds, often regain their weight.
What he found is both reassuring and depressing for those who’ve tried to maintain their weight loss. Though obesity researchers have known that the metabolism of dieters slows down, an evolutionary mechanism to stave off starvation, this study shows just how much your metabolism decelerates and for how long.
The study, led by Kevin Hall, PhD, an expert on metabolism at the National Institute of Diabetes and Digestive and Kidney Diseases, followed 14 contestants on season eight of "The Biggest Loser," for six years. It is the longest follow-up study of metabolic changes and body composition after weight loss, the authors claim. Researchers measured resting metabolism and other metabolic measures.
Though obese, the contestants all had normal metabolisms for their weight. People who are overweight tend to have higher metabolisms than those who are normal weight. But after they lost weight at the end of the show, their metabolism had slowed dramatically. That, however, was not the huge surprise for the researchers.
What surprised them was that as the contestants regained some weight, their metabolism did not rise along with the weight. It stayed low and slowed even further.
On average, the resting metabolic rate slowed by 610 kilo calories (kcal) per day. After six years, it had slowed even further by 710 kcal per day. Those with the greatest weight loss at the end of the competition experienced the greatest slowing of resting metabolic rate. This slowdown made it even more likely that they’d gain weight, unless they maintained an even greater level of exercise.
After six years, most contestants regained a significant amount of their weight, though the amount they regained varied widely. Five subjects were within 1 percent of their starting weight before they entered "The Biggest Loser competition."
The researchers do note that exercise is a key ingredient in maintaining muscle mass. DiabeticLifestyle Advisory Board Member Scott Cunneen, MD, director of bariatric surgery, Cedars-Sinai Medical Center, Los Angeles, agrees: "You don’t want to lose weight and not maintain muscle, just fat. While exercise doesn’t affect resting metabolic rate, it does help to maintain muscle mass so their bodies are still running more efficiently than if they hadn’t lost weight. But they have to work harder than they may think they do in order to keep weight off." And in this study, after six years, that phenomenon is still present. You start at a baseline, you lose weight, and your body changes in metabolism in order to get the weight back on.
“I think that the most important point in this study is that it provides scientific evidence to what we already knew—that losing weight and maintaining that loss is difficult because the body has an idea of where it wants to be,” says Dr. Cunneen. "Based on this study, there doesn’t seem to be any difference in going fast or slow. “Even though six years had passed, the body does not forget that it was made to lose weight,” he says. The body remembers what the set point is and tries to return to that weight.
For patients, the study can help them understand that the body is physiologically trying to put the weight back on. “It’s very hard to take off weight and maintain weight loss because your body is running on less energy today than it did yesterday,” says Dr. Cunneen. Because your body has this long-term memory, it continues to run on less energy, so dieters have to cut back their caloric intake, or exercise even more than they did while they were losing the weight.