Changes in the age-specific body mass index distribution among urban children between 2002 and 2018 in Changsha, China

Background It had been reported that the increase in the prevalence of childhood overweight and obesity in several developed countries over the decade was largely a consequence of changes in the upper end of the body mass index (BMI) distribution. We speculated that the change in BMI distribution among Chinese children is different from that in developed countries. Therefore, we investigated the changes in the BMI distribution among urban children in Changsha, China. Methods A secondary data analysis of the 2002 and 2018 Annual Survey on Students' Constitution and Health from Yuhua District, Changsha City, China was performed. The BMI distribution of children aged 6-15 years (n=72,061) was examined by calculating the BMI value at 5th, 50th, 85th, and 95th percentiles. Differences in the BMI value at the 5th, 50th, 85th, and 95th percentiles between 2002 and 2018 according to age and sex were calculated. Results From 2002 to 2018, the standardized rate of underweight decreased from 6.9% to 3.4%, whereas that of obesity increased from 6.1% to 13.8%. The BMI of the population increased over the 16-year period. The greatest change between the years was seen in the 85th percentile, and moderate changes were seen in the 5th and 50th BMI percentiles. Also, the greatest changes in the BMI percentiles were evident at age 12-14 years. Conclusions The whole spectrum of BMI distribution among school-aged children shifted over the 16-year study period, although the increases were more marked in the upper than lower percentiles. Health professionals and health policymakers should develop strategies and interventions aimed at preventing adverse health effects caused by this change.