Physical activity as a mediator of the associations between perceived environments and body mass index in Chinese adolescents.

This study examined whether physical activity (PA) mediated the relationships of four PA-related environmental settings (home, school, neighborhood environments and convenient facilities) with body mass index (BMI) among Chinese adolescents aged 13-18 years. Two setting indicators were assessed: (1) perceived availability of environmental resources and (2) perceived importance of environmental resources. Mediation analysis indicated that PA mediated the associations of perceived availability of the home environment, convenient facilities, and perceived importance of the school environment and BMI z-score with ratios of mediating to total effects of 46.2%, 37.1%, and 37.5% respectively. Findings suggest that PA is a mechanism by which several environmental correlates may affect adolescents' body weight.