Obesity and Severe Obesity in Youth Before and During COVID-19

Childhood obesity has remained persistently high in the United States. This study aimed to (1) assess changes in obesity prevalence and (2) examine the associations of ultra-processed food (UPF) intake and physical activity (PA) patterns with obesity, by obesity severity, before and during the COVID-19 pandemic among US 2- to 19-year-olds.

A serial cross-sectional analysis using the National Health and Nutrition Examination Survey compared data from before (2017 to March 2020) and during (August 2021 to August 2023) the COVID-19 pandemic. Obesity was determined using body-mass-index-for-age percentiles: class I obesity (≥95th percentile to <120% of the 95th percentile), class II (≥120% to <140%), and class III (≥140% of the 95th percentile). UPF intake was assessed via 24-hour dietary recalls. Participants self-reported the number of days/week they engaged in moderate to vigorous PA. Survey logistic regression models assessed the odds of increasing obesity severity by UPF intake and PA, age, sex, race, ethnicity, and household income.

Analysis included 4756 participants in the pre-pandemic period and 2501 in the pandemic period. Obesity prevalence was 21.2% pre-pandemic (N = 1072) and 22.6% during the pandemic (N = 694; P = .30). Mean %UPF intake decreased from 66.0% to 62.7% (P < .01). Before the pandemic, adjusted analysis showed youth with higher PA days had lower odds of class II obesity (odds ratio [OR] = 0.86, 95% CI: 0.76-0.97) and overall obesity (OR = 0.91, 95% CI: 0.85-0.97), with a protective effect across class I and III that did not reach significance. During the pandemic, meeting PA guidelines was also protective against overall obesity (OR = 0.86, 95% CI: 0.76-0.99). Although no significant predictors of obesity by class emerged during the pandemic, protective nonsignificant effects of PA were also observed.

Obesity prevalence trended up from before to during the pandemic, and PA was associated with obesity, whereas no distinct associations of UPF and increasing obesity severity emerged.