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.