Background:Obesity has become a major health problem among children and adolescents worldwide.This study aimed to examine the trends of overweight and obesity among childhood in China and assess their associations with family income,dietary intake,and physical activity (PA) between 1997 and 2009.Methods:Two waves of cross-sectional data of Chinese children and adolescents aged 7-17 years from the China Health and Nutrition Survey were used.Weight and height were measured following standardized procedures.Dietary intake was assessed by 3 consecutive 24-h recalls.Childhood overweight and obesity were defined using the Intational Obesity Task Force-recommended body mass index cut-offs.Multivariate linear regression analysis was used to examine the associations of family income with diet intakes and PA.Multivariate logistic regression analysis was conducted to assess the associations of overweight and obesity with family income,dietary intake,and PA.Results:The prevalence of childhood overweight and obesity increased from 12.6％ in 1997 to 22.1％ in 2009,particularly in the medium-and high-family income groups,which increased by 102.7％ and 90.3％,respectively.Higher fat intake (％ energy),and moderate and vigorous PA were significantly associated with overweight and obesity in final model (odds ratio [OR] =1.01,95％ confidence interval [CI]:1.00-1.02,P =0.004;and OR =0.99,95％ CI:0.98-1.00,P =0.036,respectively).Conclusions:The prevalence of overweight and obesity among Chinese children and adolescents has increased between 1997 and 2009.Reducing fat intake and increasing PA may help obesity prevention.