Impact of the COVID-19 pandemic on obesity: a prospective cohort study of the Canadian Longitudinal Study on Aging (CLSA)

OBJECTIVES: To examine the impact of the COVID-19 pandemic on body mass index (BMI) and obesity status among Canadian residents and explore how this association varied by sociodemographic and health status. DESIGN: Prospective cohort study. SETTING: Canada. PARTICIPANTS: 41 302 adults, aged 45-85 at baseline, participating in the Canadian Longitudinal Study on Aging. PRIMARY AND SECONDARY OUTCOMES: BMI and BMI-defined obesity were measured at baseline, follow-up 1 and follow-up 2 (FUP2), with 33% of FUP2 data (n=13 444) gathered after 16 March 2020, when COVID-19 restrictions began. Correction factors were applied for self-reported BMI and weighted generalised estimating equations assessed BMI changes before and during the pandemic. RESULTS: We found a significant interaction between follow-up time and timing of FUP2 data collection (before or during the pandemic). Participants measured during the pandemic had an excess BMI increase of 0.21 kg/m² (95% CI 0.15 to 0.28) and 1.06 times higher odds of obesity (95% CI 1.03 to 1.09) compared with prepandemic trends. Increases were more pronounced among females, middle-aged adults and those without diabetes. CONCLUSIONS: The COVID-19 pandemic was associated with a modest increase in BMI and obesity among Canadian adults. Ongoing research is needed to assess long-term trends.