COVID-19‒Related Childhood BMI Increases in China: A Health Surveillance‒Based Ambispective Cohort Analysis

INTRODUCTION: The COVID-19 pandemic‒related BMI gain and obesity prevalence changes in children have not been clearly elucidated, especially in China. This study aims to assess the impact of pandemic-related BMI and obesity prevalence change in Chinese children aged 8–12 years. METHODS: On the basis of the Health Promotion Program for Children and Adolescents in Suzhou of China, a total of 72,175 children aged 8–12 years with complete data during 2017–2020 were included. Yearly BMI z-score changes and age- and sex-adjusted BMI changes before (2017–2019) and during (2019–2020) the pandemic were calculated. Multivariate mixed linear models were used to examine the possible difference in annual BMI change rate before and during the pandemic among subgroups. RESULTS: The obesity prevalence slightly increased from 12.29% (2017) to 13.28% (2019) but substantially increased to 15.29% in 2020. The mean yearly change in BMI z-score before and during the pandemic were 0.039 (95% CI=0.037, 0.042) and 0.131 (95% CI=0.125, 0.138), respectively, yielding a difference of 0.092 (95% CI=0.087, 0.096). Similarly, changes and age- and sex-adjusted BMI increased by 0.191 (95% CI=0.179, 0.202) during the pandemic compared with those of previous years. Meanwhile, the increase in BMI changes in 2019–2020 compared with that before the pandemic was more obvious in boys than in girls and in underweight or normal-weight children than in their overweight and obese counterparts. CONCLUSIONS: BMI gain increased among Chinese children aged 8–12 years during the pandemic. There is an urgent need to formulate effective public health policies to reduce the risk of pandemic-related childhood obesity.