The Effect of the COVID-19 Pandemic on BMI in Children and Adolescents: A Retrospective Cohort Study

Background:The COVID-19 pandemic created circumstances with the potential to increase rates of overweight and obesity. We aimed to assess whether there were significant increases in BMI among a sample of children and adolescents during the year 2020compared to the two years prior to the pandemic. Methods:For this retrospective cohort study, data was obtained from the electronic medical records of 8398 children 3-17 years of age who attended3 consecutive well visits between June 1 and October 31 in 2018, 2019 and 2020 in a single center in the Midwest. Generalized linear mixed models were used to calculate the differences in average BMI and obesityrates over the three years.Results:Between 2019 and 2020, the mean BMI for the whole sample increased 3.2 percentile points (from the 70·5^th to the 73·7^th percentile; p<0·001)compared to an increase of 0.8 percentile point between 2018 and 2019 (p=0·008). The proportion of children and adolescents with obesity rose from 13% in 2019 to 15·2% in 2020 (p<0·001) compared to no significant increasefrom 2018 to 2019. Significant disparities in BMI were observed between socioeconomic and ethnic groups.ConclusionsSignificant increases in BMI and obesity rates occurred in 2020 in this sample. We propose that the circumstances surrounding the COVID-19 pandemic contributed significantly to these increases.