Legs churning, arms swinging, 16-year-old Li Peilong walks with a purpose. Huffing and puffing as the treadmill hums, his yellow shirt is soaked in sweat. He has to go 20 more minutes to finish his one-hour power walk, and although he could simply push a button and end the pain, he's determined.

While his present objective is 60 minutes of machine-assisted exercise, the young man's long-term goal is to lose weight. Yet he did not come all the way from his hometown in Hunan province to a Beijing weight loss camp by his own volition. His parents ordered him here, to GYD Fitness, where for 30 days he and 40 other overweight kids, 60% of whom are girls, will strive to get fit.

About a decade ago, a "fat camp" in China would have been as out of place as a snowboard in Thailand. With obesity on the rise, they are becoming a lucrative business, according to GYD Fitness founder Gu Yudong, who opened his facility in 2002.

Sixteen-year-old Li stands at 174cm (5'9") and weighs 110kg (242 lbs). The plan is for him to lose 10kg (22 lbs); after six days he's already shed three. The camp attempts to instill principles of self motivation, but it also dangles the carrot of an iPod Touch if kids can lose 20% of their weight.

Everyone exercises for four hours each day, two sessions in the morning and two in the afternoon. In the evenings, the program allows the kids some freedom. It's up to them to choose whether to continue being physically active, by playing badminton or swimming, or to take the relaxed route and sit down to play cards.

The kids are rewarded for their hard work by a lunch that features mainly vegetables along with a hunk of watermelon. There's no fried food in sight. Most of the kids here have poor eating habits, trainers say, emphasizing that in addition to exercise, nutrition and acquiring the right eating habits are essential. They must learn to eat more slowly and be conscious of what they're putting into their bodies, trainers say.

A quick glance around the dining room proves that the kids do not quite have the eating slowly concept down, but that does not worry the program manager, who says most of the kids will maintain their lower weight levels after the camp. The kids are not off the hook once they leave here; trainers call their homes weekly to monitor their progress.

Of course, the kids at this camp are only a small fraction of China's growing number of overweight youths. The increasing prevalence of obesity among urban schoolchildren has become a major public concern, as obesity leads to many chronic diseases such as diabetes, stroke and cancer, according to a 2009 report of the Chinese Association for Student Nutrition and Health Promotion. The report estimates that there were 120 million overweight children in China as of 2009.

In a minor but nonetheless meaningful triumph, Li completes his final minute on the treadmill, a notoriously boring piece of equipment that is often compared to a hamster. Li says music helps keep push through. A TV plays entertains a fellow camper on the next treadmill down the line, although it is ironically running a McDonald's commercial.

Li's success on the treadmill is not without consequences; his left leg suddenly cramps up. A trainer comes to help him loosen the muscles, and the cramp retreats as quickly as it came.

The treadmill has yet another victim doing its bidding, sweating, gasping and plodding forward. As he runs, Zeng Yanhaitian lacks gracefulness, but not determination. For 21-year-old Zeng, it is a simple equation: exercise burns fat, he loses weight, he scores a beautiful girlfriend. He also envisions a spiffy new wardrobe to outfit his thinner body.

"I will have them all if I lose more weight," Zeng said, who is 180cm (5'10") tall and weighs 108kg (238lbs).

Zeng has already lost a significant amount of weight, 11kg (24lbs) over the past month. The success doesn't come cheap. He has paid 16,800 yuan (US$2,629) for an intensive 42-day program and has traveled all the way from Hangzhou, capital of Zhejiang province.

The distance traveled by Li and Zeng in the quest to drop kilos is not rare. The camp attracts people from throughout the country, including Tibet, Xinjiang, and the southernmost island of Hainan, Gu said. When they finally arrive, they should be prepared to adhere to the strict eating regiment. Junk food is outlawed, and trainers patrol dorms, ready to punish violators.

"My coach caught me eating instant noodles and fried rice and made me do 500 squats," Zeng said.

He doesn't mind. He can handle being away from his family. He'll do grueling exercises. He'll eat bland food. He'll trudge through it because he believes when he steps on the scale the result will justify it all.

For Gu, Zeng's happiness gives him a strong sense of satisfaction. As a businessman, he recognizes the demand for his services will only increase. "The fat-fighting market is bullish," he said.

Now he is targeting the Zhongguancun area, a high-tech hub in downtown Beijing where sedentary white-collar workers are sensitive about their weight and suffer from various health problems.

"The number of obese people in China is ever expanding, but few are conscious of the ramifications of it," Gu said.