Why Do The 'Biggest Losers' Regain Weight Over Time?

In a recent study, a weight loss specialist confirms that many "Biggest Loser" winners tend to regain most of their weight over time.

Danny Cahill, for instance, had won Season 8 of NBC's reality television show "The Biggest Loser" on December 8, 2009, shedding more weight than anyone ever had. He lost 239 pounds in seven months.

"I've got my life back," he declared. "I mean, I feel like a million bucks."

But after that, he gained more than 100 pounds in his 5-foot-11 frame, despite his best efforts.

The Director of Washington University's Center for Human Nutrition, Dr. Samuel Klein, points out that in an aggressive program, in which you are inclined to devote a year to exercising, eating and thinning down, you cannot bank on "long term weight management success."

"This aggressive approach at short-term, is not the way to treat a life-long chronic disease like obesity," Klein says. "This requires small steady steps for life."

 "All the things that made these people obese to begin with are still there after this one year of intervention," Klein says. "And so 70 percent of the weight that they lose has been regained."

The main reason for this is "resting metabolism," which measures how many calories can be burnt by a person at rest. When the show started, all of them had normal metabolisms, ie their calories were burnt at a normal rate. However, by the end of the show, their metabolisms had slowed down drastically.

"At a higher weight, there is more body mass to maintain, and so more calories are needed. With weight loss, metabolism slows in response to body size. This is basic biology."

The study explains why people have to struggle so hard to fight obesity. Even if scientists spend millions on weight loss pills and dieting programs, most of the dieters are working against their own biology.