An epidemical survey of body mass index and obesity among 26558 elementary school children in China

Abstract

Objective To describe the distribution of body mass index (BMI) and evaluate the prevalence of overweight and obesity among first to sixth graders in 8 Chinese provinces.Methods Data came from the baseline survey of the Chinese Center for Disease Control and Prevention (CDC) funded project Study on Intervention Models for Main Chronic Diseases among children in China.A stratified random cluster sampling strategy was used to select study participants in 8 provinces,including Inner Mongolia,Jiangsu,Anhui,Shandong,Hunan,Guangxi,Gansu provinces,and Chongqing,with diverse geographical and economic level distributions in China.Counties in each province were stratified into three strata according to economic level,and one county was selected systematically from each stratum.In each county,one urban and one rural elementary school were randomly selected ; and in each school,2-3 classes were randomly selected from each of 1-6 grades.All students in these selected classes were invited for participation.Physical examination was performed by trained local CDC staff using standardized instruments to measure height and weight.Overweight and obesity were diagnosed based on the BMI classification standards for Chinese children and adolescents by Working Group for Obesity in China (WGOC).Results A total of 26558(14225 boy,12333 girl) students aged 6-12 years eventually participated in 8 provinces.The average age was 9.3 ±1.8 years old.Mean BMI among boys (17.0 kg/m2) was higher than that among girls (16.4 kg/m2,t =19.60,P＜0.01).There were statistically significant differences in mean BMI of each age group of boys and 6-11 age groups of girls between urban and rural regions and among those with three economic levels (P＜0.05).The 85th and 95th percentiles of BMI among boys aged 7-11 years in urban region were higher than BMI reference in the standards from WGOC.Lower percentiles were observed among girls aged 7-12 years in rural region.The prevalence of overweight and obesity were 9.3％ and 6.5％ among schoolchildren aged 7-12 years.The prevalence of overweight among boys (10.9％) was higher than that among girls(7.6％,x2 =88.89,P＜0.01) ; while prevalence of obesity were 8.0％ among boys and4.7％ among girls,respectively (x2 =107.17,P＜0.01).The prevalence of overweight was 11.3％ in urban and 7.4％ in rural children(x2 =131.94,P＜0.01).The prevalence of obesity was 8.7％ in urban and 4.3％ in rural children(x2 =188.99,P＜0.01).The prevalences of overweight were 10.3％,8.6％ and 9.0％ in individuals with high,medium,and low economic levels,respectively(x2 =10.76,P＜0.01) ; while the prevalences of obesity were 8.2％,5.6％,and 5.4％,respectively (x2 =51.71,P ＜ 0.01).Conclusions The overall prevalence of overweight and obesity in Chinese school children was high.The prevalence in urban region with high economic level was significantly higher than that in rural region with middle and low economic level.The nutritional and behavioral intervention programs are needed to control the rising trend of obesity in children. Key words: Body mass index; Overweight ; Obesity ; Children