Obesity among Shanghai schoolchildren has increased 24.4 percent in the last decade, according to a survey by the Shanghai Jiao Tong University.

As many as 13.3 percent of primary schoolchildren are overweight and 6.5 percent obese – higher than the world average – Shanghai Evening Post quoted the survey as saying. The report did not define overweight or obese.

Globally, an estimated 10 percent of school-aged children between 5 and 17 were overweight or obese in 2004, the World Health Organization reported. The Ministry of Health reported the same year that childhood obesity nationally had reached 8.1 percent.

Surveyors weighed 6,174 boys and 5,665 girls at 36 primary schools in Luwan, Huangpu, Yangpu and Baoshan districts and found obesity highest among boys in downtown areas of lesser-educated parents.

"Over-nutrition and lack of exercise are the causes," survey leader Cai Meiqin, vice director of the nutrition department of Shanghai Jiao Tong University School of Medicine, told the Shanghai Evening Post.

"Children sit down and do homework when they get home and watch television immediately after finishing supper."

The traditional Chinese concept that boys should be strong and girls slim also contributes to making obesity higher among boys than girls, Cai said.

Children eat too much high-calorie food and drink too many sugar-sweetened beverages, said Hong Li, a doctor treating obesity and guiding nutrition for children at the Shanghai Children's Medical Center on Sunday.

Bad living habits harmed children physically and psychologically, Hong said.

"Obese children are at risk of getting metabolism disorders such as hypertension, high cholesterol and abnormal glucose tolerance or diabetes, which used to bother old people," Hong said.

About 2.9 percent of overweight children and 6.7 percent of the obese suffered from metabolism disorders, the survey showed. The normal rate is 0.8 percent.