Associations of television viewing time with excess body weight among urban and rural high-school students in regional mainland China

OBJECTIVE: To examine the relationship between television (TV) viewing and body mass index (BMI) among adolescents in a region of mainland China. DESIGN: Population-based cross-sectional study, conducted between September and November of 2004, on a sample of enrolled high-school students aged 12-18 years. SETTING: One hundred and sixty-eight classes randomly selected from both urban and rural areas and belonging to 15 senior and 41 junior high schools in Nanjing, China, with a regional population of 6.0 million. SUBJECTS: In total 6848 students participated; 47.7 % from urban and 52.3 % from rural areas; 49.0 % male and 51.0 % female. The response rate among eligible participants was 89.3 %. RESULTS: The proportion of overweight was 6.6 % according to the criteria of overweight recommended for Chinese adolescents. Boys than girls (8.9 % vs. 4.4 %) had higher odds of being overweight (odds ratio (OR) 2.12, 95 % confidence interval (CI) 1.74, 2.60), while the proportion of overweight was significantly lower among rural students than urban students (4.5 % vs. 8.9 %; OR 0.49, 95 % CI 0.40, 0.60). Those students who watched TV for more than 7 h/week had a 1.5 times greater odds of being overweight relative to their counterparts who watched TV for 7 h/week or less (adjusted OR 1.51, 95 % CI 1.24, 1.82). Furthermore, there was a positive linear relationship between TV viewing time and BMI, even after adjusting for age, gender, residence area, time spent in study, in sleeping and in physical activity, and monthly pocket money. CONCLUSIONS: Viewing TV might increase the likelihood of being overweight for Chinese adolescents in China.