Contestants on the NBC reality show The Biggest Loser who lost huge amounts of weight in a short period of time were found to have significantly slower metabolisms several years after the show's finale, causing some to gain nearly all of the weight back, a new study published Monday found.
The study published in the peer-reviewed medical journal Obesity measured resting metabolism, which controls how many calories are burned when a person is at rest, and found that after participants lost a great deal of weight on NBC's show their metabolisms changed dramatically.
Researchers said the 14 contestants in their study had normal metabolisms for their size when season 8 began in 2009. By the end of the show, their metabolisms had slowed significantly and they were not burning enough calories to maintain their new weights, making it nearly impossible for them to keep the weight off. This is thought to be the body's natural response to a lack of food — a preventative measure in case you're actually starving.
Six years later, researchers were surprised to find that although the former contestants had gained substantial weight their resting metabolisms remained at the same, slower level as at the end of the competition.
The ex-Biggest Losers needed on average to eat 500 fewer calories than a typical person their size just to maintain their weight, the researchers said.
The study found Danny Cahill, who had successfully lost 239 pounds in seven months to win the show, had also experienced the greatest slowing of his resting metabolism. He has gained 100 pounds back since the show ended and now burns 800 fewer calories a day than would be expected for his weight, the New York Times reported.
Another contestant, Sean Algaier, a 36-year-old pastor from Charlotte, North Carolina, went from 444 pounds before the show to 289 pounds at the season finale. But he has since regained all of the weight back and is now up to 450 pounds.
"It's kind of like hearing you have a life sentence," he told the Times.
The study is the first to look at the struggles of long-term weight management after losing significant amounts of weight. Although the sample size of the research is small, it may still be helpful to researchers working to identify the causes of people struggling to keep the weight off.
"Long-term weight loss requires vigilant combat against persistent metabolic adaptation that acts to proportionally counter ongoing efforts to reduce body weight," the study's authors concluded.