On the popular reality TV series The Biggest Loser, obese people quickly shed 100 or more pounds through grueling workouts and drastic diets. New research reveals, however, that the show’s approach does not keep the pounds off long-term, because obese people’s bodies fight to regain the lost weight.
A study involving 14 former contestants found that only one managed to stay slim after six years; the rest regained most or all of the lost weight. After conducting a series of tests, researchers from the National Institutes of Health found the contestants faced a losing battle because of a phenomenon called “metabolic adaptation,” Vox.com reports. A person’s basal metabolic rate— the rate at which energy is used when the body is at rest—slows with weight loss or increased physical activity, as the body fights to maintain a stable weight.
That problem was particularly acute for the show’s obese contestants, whose bodies burned 500 fewer calories a day than expected, making it nearly impossible for them to keep the weight off. The contestants also had low levels of leptin—a hormone that signals fullness after eating—so they were constantly hungry. “Clearly, The Biggest Loser dooms contestants to either a lifetime of superhuman weight-loss efforts, or weight regain,” says obesity specialist Yoni Freedhoff. He and other experts suggest that bariatric surgery or gradual weight loss are more likely to achieve long-lasting results.