'Healthy' habits linked to childhood obesity in China

Teenaged boys from well-off Chinese families who say they are physically active and eat plenty of vegetables but few sweets are more likely to be overweight, according to a study led by researchers at the Keck School of Medicine of the University of Southern California (USC).

The study, published in the July 2011 issue of the American Journal of Health Behavior, is one of the first to examine how weight among Chinese adolescents relates to factors like sleep duration, physical activity, diet and general demographics. Most of what the research team found runs counter to Western trends.

"Findings from this large cohort of data on Chinese youth suggest that weight-related correlates might play different roles in Chinese culture than they do in Western cultures," said Ya-Wen Janice Hsu, Ph.D., M.P.H., research assistant at the Keck School's Department of Preventive Medicine and the study's first author. "This suggests that influences on obesity are society-dependent, and assumptions based on Western societies may not be applicable to Chinese populations."

As in the United States and Europe, teenagers in China who slept fewer hours and participated in more sedentary activities like watching television were more likely to be overweight, according to the study. But that's where the similarities end. Some of the disparities include:

* In China, parents with more education and more money were more likely to have obese children, whereas the same circumstances are related to a lower body mass index in Western countries.
* Chinese boys were more likely to be overweight than Chinese girls. In the United States, boys are just as likely as girls to be overweight.
* Younger children in China were more likely to be overweight than older children. The opposite is true for youth in Western societies.
* Chinese adolescents who reported frequent consumption of vegetables and infrequent intake of sweets and fast food were more likely to be overweight.
* Frequent participation in vigorous physical activity among Chinese youth was related with greater odds of being overweight.

The analysis was based on 9,023 questionnaires submitted by randomly selected middle school and high school students in seven of China's most populated urban areas: Harbin and Shenyang in the northeast, Wuhan in central China, Chengdu and Kunming in the southwest, and Hangzhou and Qingdao in the coastal regions. The sample included students from high-, middle- and low-income neighborhoods.

Possible explanations for the East-West inconsistencies noted in the study include the fact that rice is a staple grain in the traditional Chinese diet and vegetables are often deep-fried and stir-fried (weight-related factors that were not measured by the study). Industrialization and rapid economic growth have also affected Chinese diets and physical activity levels. Food consumption has increased and junk food has become more readily available. On the other hand, physical activity has decreased as more people can afford cars, televisions and computers.