"It's not only a physical problem now, but also a physiological problem," Hong's mother said.

Eventually, the family decided to pay 39,000 yuan ($5,883) to send Hong to the Renrenpang International Weight Training Camp, which started in May and will end later this month.

At the camp, everyone exercises for five hours a day, six days a week－two-hour workouts morning and afternoon, followed by an hour's training in the evening.

"We initiated fat camp for students in 2013, and 60 signed up. This summer we have more than 200 students from across the country. The youngest is age 9," said Nan Ming, a weight-loss coach.

At 1.65m tall but weighing 80 kg, 9-year-old Bobo (not his real name) has attended the boot camp for the past two years. The difference this year is that his father has joined him. "Like father like son. Neither of us likes doing sports. So I thought, 'Why not lose a year's weight in one month?'" Bobo's father said.

Ma Jun, director of the Institute of Child and Adolescent Health at Peking University, said parents should act as positive role models for their children. "Parents should set an example when it comes to getting their kids out of doors. The children of adults who do not engage in sporting activities are much less likely to undertake any exercise, which will no doubt lead to weight gain or even obesity."

According to Bobo's father, the pressure to excel academically and win places at the best schools and universities is a major contributor to the problem. That's because many children use their leisure time to study for events such as the Aoshu, the Mathematics Olympiad, and other extracurricular classes, or to practice piano and other instruments. As a result, many children are too exhausted to exercise, he said.

"Would parents accept it if being 1 kg over the standard weight resulted in 10 points being deducted from their child's score in the school entrance examination? I don't think so," he added.

To address the problem, the government established the SunnySport project in 2007. It requires primary and middle schools to hold at least one 60-minute group exercise session on days when there are no physical education classes.

Urban-rural divide

However, despite the good intentions, implementation is often poor in rural areas, according to some observers. "Schools in big cities, such as Beijing and Shanghai, may have implemented this project well. However, at schools in rural areas, where the equipment is poor and there is little attention from teachers and parents, exam scores are still king," said Hou Jingwen, an English teacher at No. 2 Middle School in Renxian county, which has a population of 370,000, in the northern province of Hebei.

According to a study published by the European Society of Cardiology last year, the proportion of overweight or obese boys in rural China soared to 17.20 percent from 0.03 percent between 1985 and 2014, while the figure for girls jumped to 9.11 percent from 0.12 percent.

"In the past two years, we have seen children from the rural areas of Shaanxi and Henan provinces attend the boot camp. Before, the number was zero," said Nan, the weight-loss coach.

Hong has lost 20 kg, and now weighs 60 kg. In the past three and half months, she has become optimistic and more self-confident. Next month, she will return to Chengdu and restart school.

"I hope that next time I come to Beijing, it will be to start my life at college," she said.