Report on Childhood Obesity in China （8）： Effects and Sustainability of Physical Activity Intervention on Body Composition of Chinese Youth

Objectives To determine whether a large-scale physical activity intervention could affect body composition in primary school students in Beijing, China. Methods The study design was one-year cluster randomized controlled trial of physical activity intervention （20 rain of daily exercise in the classroom） with an additional year of follow-up among 4 700 students aged 8-11 years at baseline. Results After the one-year intervention, BMI increased by 0.56 kg/m2 （SD 1.15） in the intervention group and by 0.72 kg/m^2 （SD 1.20） in the control group, with a mean difference of-0.15 kg/m^2 （95% CI： -0.28 to -0.02）. BMI z score decreased by -0.05 （SD 0.44） in the intervention group, but increased by 0.01 （SD 0.46） in the control group, with a mean difference of-0.07 （-0.13 to -0.01）. After another year of follow up, compared to the control group, children in the intervention group had significantly lower BMI （-0.13, -0.25 to -0.01 ）, BMI z score （-0.05, -0.10 to -0.01）, fat mass （-0.27 kg, -0.53 to -0.02） and percent body fat （-0.53, -1.00 to -0.05）. The intervention had a more pronounced effect on weight, height, BMI, BMI z score, and body composition among obese children than among normal weight or overweight children. Compared to the control group, the intervention group had a significantly higher percentage of children who maintained or reduced their BMI z score at year 1 （P-0.008） and year 2 （P=-0.04）. Conclusions These findings suggest that 20 min of daily moderate to vigorous physical activity during the school year is a feasible and effective way to prevent excessive gain of body weight, BMI, and body fatness in primary school students.