Longitudinal Trends in the Weight Status Prior, During, and Post-School the COVID-19 Pandemic Among Children Aged 6 to 11 Years – Brazil, 2020–2025

Previous studies suggested that the COVID-19 pandemic exposed children to an increased risk of greater body weight accumulation; however, the evidence found is limited to examining relatively short periods in children from Asian, European, or North American countries and, in most cases, using cross-sectional designs, while studies with longitudinal designs are scarce. To our knowledge, to date, no study involving Brazilian children has examined temporal trends in body weight during the pandemic period using a longitudinal approach. Objective: To report temporal trends in the weight status of children aged 6 to 11 years prior, during, and post-school closures in response to restrictions imposed by the COVID-19 pandemic, using a six-year school-based cohort design (2020–2025). Method: Weight status was analyzed using the body mass index and diagnostic criteria proposed by IOFT. Initial data collection took place in 2020 (pre-pandemic period), in 2021 and 2022 (pandemic period), and in 2023, 2024, and 2025 (post-pandemic period), after the reopening of schools. Results: The data collected confirmed that restrictions imposed to mitigate the adverse impact of the COVID-19 pandemic, including the full or partial closure of schools, substantially increased children's weight above what would be expected for their gender and age. After two years of the pandemic period, 23% of children identified in the pre-pandemic period with normal body weight migrated to overweight, while 34% of overweight children became obese. Data equivalent to the post-pandemic period showed signs of a reduction in the excess body weight accumulated during the pandemic; however, the prevalence rates of overweight and obesity remained significantly higher than in the pre-pandemic period. Conclusion: The findings suggest that the harmful effects contributing to the greater accumulation of body weight during the COVID-19 pandemic were not reversed spontaneously, even five years after its onset. Therefore, specific actions to prevent, combat, and control overweight and obesity are essential to avoid present and future adverse consequences for children's health.