Impact of the COVID-19 Pandemic on BMI and Obesity among Underrepresented Populations: A Longitudinal Analysis of the All of Us Dataset

Introduction : The COVID-19 pandemic and its prevention measures (e.g., quarantine, social distancing, and shutdown) significantly affected people’s physical activity and lifestyle, potentially increasing Body Mass Index (BMI) and risk of obesity. This study provides a comprehensive analysis to examine changes in BMI and obesity rate across pre-COVID, COVID, and post-COVID periods, and to identify the sociodemographic correlates of BMI and obesity change. Methods : Longitudinal electronic health record data from the All of Us Research Program for adults ≥ 18 years with at least one BMI record in each period (N = 38,632) were analyzed. Periods were defined as pre-COVID (Jan 1, 2018–Mar 12, 2020), COVID (Mar 13, 2020–Dec 31, 2021), and post-COVID (Jan 1, 2022–Oct 31, 2023). We modeled BMI with a linear mixed-effects model and obesity (BMI ≥ 30) with a GEE logit model, adjusting for age, sex, race, ethnicity, income, and employment; time was modeled with linear and quadratic terms, and we tested time × subgroup interactions. Results : Mean BMI increased from 30.05 pre-COVID to 30.14 during COVID, then declined to 29.96 post-COVID; obesity prevalence followed a similar pattern (43.5% → 44.1% → 43.2%). In adjusted models, linear time effects were positive and the quadratic terms negative for both outcomes, indicating non-linear (increase-then-partial-reversal) trends (BMI: β_time = 0.216; β_time² = −0.018; obesity: aOR_time = 1.052; aOR_time² = 0.996; all p < 0.001). Female, Black and Hispanic/Latino participants had higher BMI and greater odds of obesity than their counterparts, while higher income showed a protective association. Significant time × subgroup interactions were observed, with age and employment status showed the most consistent effects across both outcomes. Conclusion : BMI and obesity increased during the pandemic and partially reversed afterward, but persistent disparities remained, with higher risk among women, Black and Hispanic/Latino adults, and lower-income groups. Results highlight the impact of COVID-19 on obesity risk and emphasize the need for proactive measures to promote healthier lifestyle and weight management strategies for vulnerable groups in future public health preparedness plans.