Association and potential mediators between socioeconomic status and childhood obesity in China: findings from a national cohort study

Objective: Socioeconomic status (SES) is associated with childhood obesity, but the underlying factors remain unknown. This study aimed to identify mediators that may explain SES disparities in childhood obesity in China. Methods: Nationally representative longitudinal data from the China Education Panel Survey of 11 019 children (13.03 ± 0.79) collected from 2013‒2014 to 2016‒2017 academic years. Overweight/obesity was defined using Chinese national body mass index cut-points. Principal component analysis was used to convert the four SES indicators (maternal and paternal education, and occupation) into one comprehensive variable. Mediation analysis for SES disparities in childhood obesity was conducted using structure equation models. Results: The prevalence of overweight/obesity was 12.8%, and was higher in boys than in girls (17.8% vs. 7.6%, P < 0.001) at baseline. Among boys, relative risk (RR) of obesity was 1.23 (95% CI: 1.09 to 1.40, P < 0.001) for per unit change in SES. There was no significant association between obesity and SES among girls. Mediation analyses showed that among boys, birth weight, being the only child in the family and children's self-perceived weight status mediated 70.0% of the effects of SES on obesity. No mediation effect was detected in girls. Conclusions: Chinese boys are more likely to be overweight or obese than girls. SES may impact childhood obesity through birth weight, being the only child in the family and children's self-perceived body weight status in boys, but not in girls. More attention should be made to address childhood obesity in high SES families among boys. Interventions targeting at these mediators are needed.