Worldwide prevalence of childhood obesity has increased substantially in the past decades and was associated with significant impact on child's physical and social development. High energy-dense foods and physically inactive are the major lifestyle risk factors for childhood obesity^{(Reference Mistry and Puthussery1)}. Therefore, this study aimed to determine the prevalence of overweight and obesity among the Chinese school-aged children, and the relationships between childhood obesity and lifestyle factors, particularly on physical activity and dietary intake.

Data for this study was obtained from Chinese Health and Nutrition Survey (CHNS) 2010–2012^{(Reference Popkin, Du and Zhai2)}. Social-demographic and physical activity data were collected using structured questionnaires. Dietary intake was assessed using a 100-item FFQ. Overweight and obesity were defined as BMI at 85th-95thand >95th percentiles, respectively, specified for age and gender⁽³⁾. 24,722 children aged 6–17 years old from 31 provinces were recruited using a multistage random-cluster sampling process2. Of those, 2,617 participants who had complete data on the aforementioned parameters were included in this study. Statistics: Multivariate logistic regression analysis was performed to determine the associations between lifestyle factors and the odds of overweight and obesity. Mann-Whitney test was performed to assess the difference in average daily food consumption between the low and high physical activity groups.

16.3% of our study participants were found to be overweight, and of those, 7.3% were obese. Children using motorized transportation method (including car, bus, taxi or other public transport) to school and who spent ≥3h/day of sedentary activity were associated with increased odds of overweight and obesity (OR = 1.296, CI = 1.030-1.631; p = 0.027 and OR = 1.485, CI = 1.020-2.164; p = 0.039, respectively) compared to non-motorized transportation and <2h/day of sedentary activity, after adjusting for covariates gender, age, income level, resident type, and total energy intake. Interestingly, children who spent ≥60mins/day of physical activity were significantly associated with increased odds of overweight and obesity (OR = 1.472, CI = 1.185-1.828; p < 0.001) compared to <60mins/day. This may be explained by the increase in average daily consumption of fish, eggs, dairy products, fruits, vegetables, legumes, snacks, and beverages, in the physically active group (≥60mins/day) (p < 0.05). Moreover, ≥41.5g/day of egg, and ≥113.3g/day of dairy product consumption were associated with increased odds of overweight and obesity (OR = 1.645, CI = 1.119-2.417; p = 0.011 and OR = 1.432, CI = 1.000-2.053; p = 0.050, respectively), compared to lower consumption. However, such associations did not reach statistical significance after adjusting for covariates (p > 0.05). No other dietary factor alone was found significantly associated with overweight and obesity.

Motorised transportation to school and sedentary time were significantly associated with increased risk of childhood overweight and obesity. Similar finding was found in physical activity; however, this may be due to the increase in total energy intake associated with higher physical activity level. Dietary factor alone was not found to be significantly associated with overweight and obesity.