[Analysis on the trend of overweight and obesity of children and adolescents in 9 provinces of China from 1991 to 2015].

To analyze the trends of overweight and obesity of children and adolescents in 9 provinces of China from 1991 to 2015. A total of 14 888 children and adolescents aged 6-17 years with complete data were selected from the China Health and Nutrition Survey from 1991 to 2015. The definitions of overweight and obesity were defined using the international body mass index (BMI) cut-offs for child overweight and obesity established by the International Obesity Task Force in 2000 (hereinafter referred to as 'IOTF Standard'), the growth reference for school-aged children and adolescents established by the World Health Organization in 2007 (hereinafter referred to as 'WHO Standard'), the BMI cut-offs for screening overweight and obesity in Chinese children established by Li Hui et al. in 2009 (hereinafter referred to as 'Expert Standard'), and the screening thresholds for overweight and obesity in Chinese school-age children and adolescents released by the National Health and Family Planning Commission in 2018 (hereinafter referred to as 'Industry Standard'). Multivariable linear regression model was used to examine the trends in BMI values from 1991 to 2015, and multivariable logistic regression model was used to examine the trends in the prevalence of overweight and obesity from 1991 to 2015. After adjusting for the age, sex and region, BMI values increased from 17.26 kg/m(2) in 1991 to 18.72 kg/m(2) in 2015 ( value for trend <0.001). The prevalence of overweight defined by the IOTF Standard, WHO Standard, Expert Standard, and Industry Standard increased from 4.06%, 5.37%, 5.16%, and 4.27% in 1991 to 13.58%, 16.23%, 13.30%, and 11.70% in 2015, respectively (all values for trend <0.001), and the prevalence of obesity increased from 1.02%, 1.86%, 2.24%, and 2.41% in 1991 to 7.45%, 10.75%, 12.08%, and 12.74% in 2015, respectively (all values for trend <0.001). The BMI values and prevalence of overweight and obesity increased significantly in Chinese children and adolescents from nine provinces from1991 to 2015.