A 3-year Longitudinal Study of the Effects of Physical Activity and Sedentary Behaviors on Childhood Obesity in China: The Childhood Obesity Study in China Mega-Cities

Abstract

Objectives: Examine school children’s physical activity (PA) and sedentary behaviors (SB) during 2015-2017 and study their effects on children’s weight status and their relevant gender differences in China. Methods: This open cohort study included students from 5 major cities (Beijing, Shanghai, Xi’an, Nanjing, and Chengdu) across China. Data were collected from students in 2015, 2016, and 2017 (n = 5,535) and from their parents and school personnel. Children’s weight, height, and waist circumference were measured. SB and PA factors were evaluated using questionnaires. Mixed effects models examined the relationship between weight status and PA/SB-associated factors using this longitudinal data. Results: These children had high rates of obesity (12.4%, 95% CI 11.6%-13.3%) and central obesity (28.1%, 95% CI 26.9%-29.3%) during 2015-2017. Boys were more likely to be obese (16.5% vs. 8.4%) and central obese (36.3% vs. 19.8%) and spent more time in screen viewing than girls (hours/week ± SD: 2015, 1.8 ± 2.5 vs. 1.5 ± 2.0; 2016, 2.0 ± 2.4 vs. 1.8 ± 2.5; 2017, 1.7 ± 2.3vs. 1.4 ± 2.1 hours/week). Those who walked ＜ 5 minutes on their average daily walk to school were more likely to be obese (OR: 1.96, 95% CI 1.03-3.73) than those who spent ≥ 15 minutes on walking to school. When stratified by gender, this higher risk was only observed in girls (OR: 3.01, 95% CI 1.09-8.35). Children who spent more time in screen viewing were more likely to be obese (OR: 1.13, 95% CI 1.06-1.21) and have central obesity (OR: 1.05, 95% CI 1.02-1.09). The association for obesity was consistent in boys and girls (boys, OR: 1.15, 95% CI 1.05-1.25; girls, OR: 1.12, 95% CI 1.00-1.24). Conclusions: More screen time and less active time were risk factors for developing obesity in urban Chinese children. The associations varied by gender.