About 13.3 percent of local children are overweight and 6.5 percent are obese, according to a newly released survey.
The obesity rate among local schoolchildren has grown by 24.4 percent in the past decade and is close to that found in Western countries, experts said.
Children from downtown areas are fatter than those in the suburbs, children from low and middle-income families are more obese than those from high income ones and male students are plumper than female students, the survey found.
Being born a big baby, with inherent big-body weight, consumption habits and a couch potato-like lifestyle are major causes, researchers found.
Unhealthy lifestyles and wrong concepts about child-raising among parents and grandparents are important risk factors, said experts, who researched local children's obesity and metabolism disorders through the survey covering 11,839 students from 36 primary schools in Luwan, Huangpu, Yangpu and Baoshan districts.
"It is a comprehensive survey since we not only included weight measurements and questionnaires but checked their blood pressure, cholesterol and glucose levels," said Cai Meiqin from the nutrition department of Shanghai Jiao Tong University's School of Medicine, which conducted the survey.
Experts called for more awareness of the issue, as being overweight or obese during childhood increase the risk of hypertension, diabetes and heart diseases as an adult. Obesity during childhood can also cause other side effects, such as poor sexual development in males and a negative impact on mental development and social ability.
In the survey, about 0.8 percent of normal-weight children had metabolism disorders, while the percentage rose to 2.9 for overweight children and 6.7 for obese ones.
Being a big baby is a factor, experts found. Some 35.7 percent of overweight children and 43.3 percent of obese children weighed more than 4.5 kilograms when born.
Soft drinks are another factor, as more than half of obese children consumed sugary drinks more than three times a week. Spending too much time watching TV and on the computer and late night snacking also play a role, Cai said.
"It's difficult to control their weight if they don't change their lifestyle," she added.