Chinese teens who think of themselves as fat, even if they were normal or underweight, are at a greater risk for depression and school-related stress, a new USC study has found.

Girls who said they were overweight reported an overall grade point average of 3.06 versus 3.20 for other girls, according to the study of nearly 7,000 middle- and high-school students in seven Chinese cities. Boys who felt obese reported being more prone to rudeness and losing their tempers. The study appears in the March issue of the American Journal of Health Behavior.

"Thin as the ideal body type is a relatively new standard in China, a trend fueled by increased wealth and media exposure to Western lifestyle," said lead author Bin Xie, an assistant research professor in the USC School of Social Work.

Weight perception may trump actual body weight in predicting negative psychological effects, Xie said.

"The major point here is that misperception has an important impact on academic performance and a person's psychological experience," Xie said.

In another study published in the March edition of Preventive Medicine, Xie found that Chinese youth's unhappiness with their weight was significantly related to Western media exposure, leading some girls to adopt such unhealthy behaviors as smoking or drinking.

"The studies underscore the importance children place on body image," Xie said.

The data for the two studies came from an ongoing longitudinal health promotion study of Chinese adolescents in seven large cities on the Chinese mainland.

The research was supported by the USC Pacific Rim Transdisciplinary Tobacco Use Research Center, which is funded by the National Institutes of Health and the Sidney R. Garfield Endowment. Additional support was provided by the Centers for Disease Control and Prevention in the seven participating cities in China and the Institute for Health Education in Kunming, China.