The Effects of Physical Activity and Sedentary Behaviors on Overweight and Obesity among Boys may Differ from those among Girls in China: An Open Cohort Study

Abstract

Background: Childhood overweight and obesity are increasing steadily in China, yet few studies have focused on exploring the risk factors associated with sex differences.

Objectives: We tested the hypothesis that the effects of physical activity and sedentary behaviors on overweight and obesity differ between boys and girls.

Methods: We used data collected from 4520 children and adolescents aged 6-18 y from 2004 to 2015 in an ongoing open-cohort study, the China Health and Nutrition Survey, to explore the effects of physical activity and sedentary behaviors on the risk of overweight and obesity in Chinese children and adolescents. We collected detailed information on physical activity and sedentary behavior along with dietary data, and we measured height and weight with standardized methods. We used random-effects logistic regression models to analyze the associations between total physical activity and sedentary behavior and overweight and obesity.

Results: The effects of sedentary behaviors and vigorous physical activity were only significant among girls. Vigorous physical activity decreased the risk of overweight and obesity by 63% (OR: 0.37; 95% CI: 0.20, 0.67) among girls ages 6-11 y and by 54% (OR: 0.46; 95% CI: 0.25, 0.85) among girls ages 12-18 y. High sedentary-hour values increased the risk by 96% (OR: 1.96; 95% CI: 1.09, 3.54) among girls ages 12-18 y. None of the effects were significant among boys.

Conclusion: Low physical activity and high sedentary time increase the risk of overweight and obesity, particularly among adolescent girls. The effects of physical activity and sedentary behaviors on overweight and obesity among boys may differ from those among girls. Sex effects should be taken into consideration when promoting physical activity. Whether this sex difference is a result of high male preferences in China that preclude many activities among boys or other factors requires further study.

Keywords: adolescent overweight; childhood obesity; physical activity; sedentary hours; sex.