Increased obesity risks for being an only child in China: findings from a nationally representative study of 19,487 children

Objectives Given the rapid demographic transition and obesity growth in China, it is important to study how the large only-child population (≈100 million) might contribute to the obesity epidemic. This study evaluated associations of only-child status with weight and energy expenditure–related behaviors in China and examined how the associations may vary by sex and urbanicity. Study design Secondary analyses of nationally representative cross-sectional data from China Education Panel Survey: Junior Cohorts 2013–14, which included 19,487 students from 112 middle schools in 28 regions across China. Methods We used propensity-score–weighted multilevel models to test associations between only-child status and weight outcomes. Results Compared with sibling-sons, only-sons had higher body mass index (BMI) (Beta = 0.32, P < 0.05) and higher risks of overweight (OR = 1.24, 95% CI = [1.07–1.45]) and obesity (OR = 1.29, 95% CI = [1.02–1.64]); and spent less time on TV watching (Incidence rate ratio (IRR) = 0.89, 95% CI = [0.81–0.98]), internet use (IRR = 0.87, 95% CI = [0.79–0.96]), after-school sports (IRR = 0.91, 95% CI = [0.83–0.99]), and household chores (IRR = 0.85, 95% CI = [0.80–0.92]). Overweight/obesity risks for only-sons were particularly pronounced in urban China, where only-sons were 36% more likely to be overweight and 43% more likely to be obese than sibling-sons. Only-daughters had a higher risk of obesity (OR = 1.43, 95% CI = [1.01–2.04]) than sibling-daughters. However, the association was not significant for either urban girls or rural girls examined separately. Only-daughters in rural areas spent less time helping with household chores (IRR = 0.88, 95% CI = [0.80–0.97]) than sibling-daughters. Conclusions Future childhood obesity interventions should pay special attention targeting the large young only-child population in China.