The grueling boot-camp workouts on NBC's The Biggest Loser help contestants lose large amounts of body fat while preserving their muscle mass, a new study shows.
Participants on the show do intense aerobic and strength-training exercises for four to six hours a day and follow a low-calorie diet as viewers watch the pounds melt away.
But how does all this affect the dieters' body composition and metabolism?
To find out, researchers at the Pennington Biomedical Research Center in Baton Rouge went to the set of the show during Season 8 in 2009, when Oklahoma native Danny Cahill won after losing 239 pounds.
The scientists measured the weight, body composition and resting metabolic rate of the 16 participants at the start of the show, at Week 6 and at Week 30, the finale.
The findings, presented this week at the meeting of the Obesity Society in San Diego:
*Overall, the contestants dropped from an average 49% body fat to 27%.
*After 30 weeks, participants lost an average of 128 pounds; 81% was body fat and 19% was fat-free mass, mostly muscle.
This huge loss of body fat and minimal loss of muscle "is quite remarkable," says lead author Darcy Johannsen, assistant professor of skeletal muscle physiology at Pennington. "This means the vigorous exercise helped the contestants preserve their muscle mass, which is the most metabolically active tissue of the body."
You don't want to lose muscle mass
Dieters don't want to lose muscle mass because it is responsible for resting metabolic rate, regulation of core body temperature and maintenance of optimal function and quality of life as the body ages, she says. You need strong muscles and bones to stay active.
Senior author Eric Ravussin, director of the Nutrition Obesity Research Center at Pennington, says the intensity and amount of exercise that contestants do on the show are not reasonable for most obese people. "They work out with the trainers for four to six hours a day, and it's heavy-duty. There is nobody who can do that in real life -- unless you are chasing a quarter of a million dollars (the top Biggest Loser prize). That's a pretty good incentive."
You do want to lose the loose skin
Cahill, a motivational speaker, says he has regained about 20 pounds and weighs about 205. He attributes most of that gain to muscle mass he has put on, especially in his upper body. "Things are going well," he says.
Cahill had plastic surgery to remove about 10 to 15 pounds of loose skin from his torso, abdomen, chest and back, which was documented Tuesday on the syndicated talk show The Doctors (thedoctorstv.com).
Plastic and reconstructive surgeon Andrew Ordon, one of the hosts of the show, performed the operation with the help of his partner, plastic surgeon Ritu Chopra. Ordon says the surgeons removed "4 square feet of skin."
Cahill, 41, is in great shape, and that helped, Ordon says. "When we were in there, his muscle was great. He had worked out so hard that his muscle tone was excellent.
"It means it's a better result. He looks darn good. You can see some definition in his abs."
Said Cahill on the show: "I really feel like I can take my shirt off in public now and not be embarrassed about it."
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