Fat Chance - The Science of Appetite - TIME

Forget Survivor and The Amazing Race and all the other reality shows that feature generally good-looking, generally physically fit people running around doing generally silly things. 

In the U.S.'s nation of overstuffed couch potatoes, The Biggest Loser hits closer to real reality by combining the TV genre's outlandishness and greed with the more mundane goal of shedding unwanted kilograms. With its $250,000 grand prize and dramatic stories of weight loss, the show is a natural for the nation's chubby, if not huddled, masses yearning to breathe free without having to unbutton their pants after a meal. More than 100,000 people applied to be on the show's fourth season, now in production, and more than 5 million have had their diets assessed on the show's biggestloserclub.com.

But while the message of the show is inspiring, it is also unrealistic. The Biggest Loser achieves rapid transformations—contestants often drop more than 9 kg in a week—through calorie restriction, endless exercise and no small amount of dehydration that occurs behind the scenes. Ryan Benson, 38, an actor who works for a DVD distributor in Los Angeles, lost 55 kg to win the first season in January 2005 but says he regained 14.5 kg within five days simply by drinking water. Matt Hoover, 31, a motivational speaker based in Seattle, had a 7-kg rebound within a day of winning Season 2. Last season's runner-up, Kai Hibbard, 28, an aerobics instructor in Alaska who says she spent the night before her final weigh-in hopping in and out of a sauna for six hours, consumed only sugar-free Jell-O for several days and wolfed down asparagus, which is a natural diuretic. "It's amazing the things you learn in a weight-loss competition," she says.

The show tries to prevent unhealthy behavior by making contestants keep food journals (to make sure they're not starving themselves) and threatening penalties if tests show they are too dehydrated (although an executive producer says no violations have been uncovered yet). 

But like the $55 billion U.S. diet industry, The Biggest Loser places the bulk of its emphasis on shedding kilograms rather than maintaining the loss. After all, a show called The Biggest Maintainer wouldn't have nearly the same zing. Contestants learn how to make healthy choices, but total-immersion exercise accounts for most of the weight loss. And it's not as hard to work out for four or more hours a day when urged on by professional trainers. It's also easier to resist high-calorie temptations when the cameras are rolling. Two and a half years after Benson's final weigh-in at 94 kg, the new dad has slipped out of the spotlight and into old habits. "No one sees me get an apple pie in the drive-through," says Benson, whose weight now hovers at around 136 kg.

Still, by keeping 14 kg off for more than a year, he's something of a rarity. The U.S. National Weight Control Registry, which tracks the habits of some 5,000 successful maintainers, cites a study showing only a fifth of dieters with a history of obesity sustain a loss of 10% of their body weight for a year or more. "The best predictor of the ones who are not going to regain are the ones who are doing the most physical activity," says Dr. Holly Wyatt, an obesity expert at the University of Colorado. She says most registrants exercise, on average, at least an hour a day.

Who has time for that? Kelly Minner, for one. The first-season runner-up dropped from 110 kg to 74 kg by the finale and now weighs 63 kg. A school administrator in Bethlehem, Pennsylvania, Minner, 31, says she works out from one to four hours a day, six days a week. She exercises while watching TV—and did so throughout our phone interview. For motivation, she keeps a souvenir from the show in her office: a life-size photo of her old fat self. Other winners share this strategy. Hoover, who has gained 24 kg since November 2005, sees his cardboard cutout every day in his garage. Last season's winner, Erik Chopin, 37, who owns a deli in North Babylon, New York, and since December has put on 10 of the 97 kg he lost, keeps a photo on his fridge taken when he weighed 185 kg.

The series added a more realistic component last season when 36 of its 50 contestants competed from home sans trainer. "They really got none of the bells and whistles," says the show's physician, Dr. Robert Huizenga. Well, almost none: they were still eligible to be tapped for the main show, and the at-home winner got $50,000. If the producers proceed with plans for a reunion episode later this year, it will be interesting to see how the contestants have fared since they went off camera and stopped racing for a cash reward.