Health experts cringe during episodes of ''The Biggest Loser.'' The dramatic and rapid weight-loss of the reality show's participants and the often demeaning tactics are not hallmarks of a successful lifestyle change, they say.

But the show, set to begin its 10th season, has inspired thousands of weight-loss competitions nationwide, from a small group of friends on Facebook vying for bragging rights to dozens of teams in a corporate-sponsored contest trying to win a cash prize. People are signing up for contests at their gym and online at sites like WeightLossWars, which allows users to create and track their own competitions.

This summer, the online network HealthyWage, is holding the first nationwide team weight-loss competition. On Aug. 15, the team with the greatest percentage of weight lost will win $10,000.

Despite the shortcomings of "The Biggest Loser,'' said Dr. Christina Jenkins, the chief medical officer for HealthyWage, "The show played a significant role in shedding light on the hard work needed to effect change, and in providing a framework by which weight loss success might be achieved."

But is losing weight to win an effective motivation? What happens when the competition is over? Can people maintain the will to put on the running shoes and pass on dessert when the pressure is off?

Participants say competitions have changed their lives. Because of the success, many businesses and gyms have held consecutive competitions with no signs of stopping. Wildwood was the first branch of the YMCA of Greater St. Louis last year to host a competition, and now about half of the 18 branches play host, some with waiting lists, said health and wellness director LeAnn Harris. More than 350 members have lost a total of over 6,000 pounds.

"Members are looking better and feeling better and losing weight," Harris said. "When you feel good, the word just spreads."

Tom Koneck, 30, of Chesterfield, is optimistic the focus required to have a shot in the HealthyWage competition will finally put an end to his yo-yo dieting. Midway through the competition, which started May 15, Koneck said he is controlling meal portions, not snacking at night and hitting the gym after work.

"For a person like me, the question is how to get into the habit of living that way, of being vigilant in the calories you burn and consume," Koneck said. "There has to be some sort of catalyst."

Half regain weight

Success depends on a few key factors, experts say. Follow-up stories on former ''Biggest Loser'' participants show that about half have regained significant amounts of weight after the cameras left.

"Once the competition is over, all the things that made you eat the way you were eating before the competition are still there," said Sam Klein, director of the Center of Human Nutrition at Washington University School of Medicine. "Things like genetics, lifestyle and social pressures are all still there. What is not there is the competition and support from the group."

Many agree that losing weight only to win is not likely to instill lifelong habits. "The act of competing, in and of itself, is probably only a good idea for a small percentage of Americans — likely those who grew up playing sports or have 'alpha' or risk-taking personalities," said Jenkins, also a member of the adjunct faculty at Mount Sinai Medical Center in New York.

But during the course of competitions, which usually last around three months, Jenkins said, participants can learn proven behaviors that lead to permanent change. Incentives can work as a "turbocharger," she said, to create systems of accountability, support and discipline that don't end after crossing the finish line.

"Enrolling in an 'official' competition, as opposed to say, joining a gym by yourself after New Year's, can serve as a forcing function to make one prioritize weight loss as a goal and to concentrate efforts for a sustained period of time," she said, "which helps develop lifelong healthy habits."

Kelly Oplt, 41, won the Wildwood YMCA's 16-week competition that ended in April. She lost 50 pounds and has dropped 20 more since. The camaraderie she developed with Y members during the contest continues to motivate her as she visits the gym. She still doesn't want to let them down. "It's a social environment now," she said. "It's kind of like going to a healthy 'Cheers' where everyone knows your name."

Losing pounds together

The 12-member team who won a hospital-wide weight-loss competition at St. Clare Health Center in Fenton may be the perfect example of competition's habit-forming power. The group of IT employees entered the contest figuring it would be more fun to lose weight together, and 218.7 pounds later, it proved true. They shared recipes and found healthy food they liked. They stopped bringing junk food to the office. They studied calorie counts of area restaurant entrees.

"For the first time, we were all saying 'Don't eat that,' " said member Aaron Schiltz, 33, of St. Louis, who lost 25 pounds and weighs what he did in high school.

Despite the competition ending nearly three months ago, they are training for triathlons, running in 5K races and even continuing weekly weigh-ins. French fries haven't reappeared on the cafeteria table.

"The most important thing to make part of our day is our work-out, as opposed to being the last thing we schedule," said Julia Kientzy, 39, of Webster Groves. "It's become an automatic thing we do every day."

The individual winner, Brian Gaffney, 27, of Webster Groves, was also a member of the team. He lost 57 pounds, or nearly 18 percent of his body weight. He's in the habit of staying on the move, he said, getting out of his chair instead of sending e-mails to co-workers and walking to the store. He loves cucumbers and carrots.

"It's nice when it becomes a natural decision, when you've made a permanent change in your lifestyle," Gaffney said. "I don't even have to think about the choice."

Hanson Professional Services, a nationwide engineering firm with an office in Maryland Heights, has been holding competitions every 14 weeks for two years, and even started "Best Maintainer" competitions to help employees keep the weight off, said Tony Camella, vice president of human resources.

"The unusual part is that it's stuck around for so long, and it's not something we've really had to push or enforce," Camella said. "The fact of the matter is, when people are motivated to do something themselves, it's much more powerful."