On The Biggest Loser, contestants successfully shed hundreds of pounds with intense dieting and exercise, but when they returned to their normal lives, many quickly regained the weight.
The study, profiled in The New York Times, found that the diet tactics on The Biggest Loser may have permanently damaged the contestants’ metabolisms, to the point where they are physically unable to keep the weight off. Lets see some numbers.
Danny Cahill (46)
WEIGHT Before show, 430 pounds; at finale, 191 pounds; now, 295 pounds
METABOLIC RATE Now burns 800 fewer calories a day than would be expected for a man his size.
Dina Mercado (35)
WEIGHT Before show, 248 pounds; at finale, 173.5 pounds; now, 205.9 pounds
METABOLIC RATE Now burns 437.9 fewer calories per day than would be expected for a woman her size.
Sean Algaier (36)
WEIGHT Before show, 444 pounds; at finale, 289 pounds; now, 450 pounds
METABOLIC RATE Now burns 458 fewer calories a day than would be expected for a man his size.
It has to do with resting metabolism, which determines how many calories a person burns when at rest. When the show began, the contestants, though hugely overweight, had normal metabolisms for their size, meaning they were burning a normal number of calories for people of their weight. When it ended, their metabolisms had slowed radically and their bodies were not burning enough calories to maintain their thinner sizes.
Researchers knew that just about anyone who deliberately loses weight — even if they start at a normal weight or even underweight — will have a slower metabolism when the diet ends. So they were not surprised to see that “The Biggest Loser” contestants had slow metabolisms when the show ended.
What shocked the researchers was what happened next: As the years went by and the numbers on the scale climbed, the contestants’ metabolisms did not recover. They became even slower, and the pounds kept piling on. It was as if their bodies were intensifying their effort to pull the contestants back to their original weight.
Slower metabolisms were not the only reason the contestants regained weight, though.The investigators found at least one reason: plummeting levels of leptin. The contestants started out with normal levels of leptin. By the season’s finale, they had almost no leptin at all, which would have made them ravenous all the time. As their weight returned, their leptin levels drifted up again, but only to about half of what they had been when the season began, the researchers found, thus helping to explain their urges to eat.
Leptin is just one of a cluster of hormones that control hunger. In a one-year studyfunded by Australia’s National Health and Medical Research Council, Dr. Joseph Proietto of the University of Melbourne and his colleagues recruited 50 overweight people who agreed to consume just 550 calories a day for eight or nine weeks. They lost an average of nearly 30 pounds, but over the next year, the pounds started coming back.