The impact of COVID-19 lockdowns on the body mass index of people living with obesity: A UK retrospective cohort study using the UK Clinical Practice Research Datalink.

Background: Restrictions implemented by governments during the coronavirus disease 2019 (COVID-19) pandemic affected people's eating habits and physical activity. We investigated the effect of COVID-19 lockdowns and restrictions on body mass index (BMI) and weight in a UK population, according to BMI class, sex, age and ethnicity.

Methods: This retrospective observational cohort study used the Clinical Practice Research Datalink AURUM database. Baseline spanned from 22 March 2017-22 March 2020, and the follow-up lockdown period was from 23 March 2020 (start of the lockdown in the UK) to 13 March 2021. The descriptive analysis included individuals with ≥ 1 valid BMI/weight measurements during both the baseline and follow-up periods, while the model-based analysis comprised individuals with ≥ 1 valid measurement(s) during baseline. Results were stratified by baseline BMI category, sex, age and ethnicity.

Results: In the descriptive analysis (n = 273,529), most individuals did not change BMI category post-lockdown (66.4-83.3%). A greater proportion of women (12.6%) than men (9.5%) moved up BMI categories post-lockdown. Compared with older groups, a higher proportion of individuals < 45 years old increased post-lockdown BMI category. The model-based analysis (n = 938,150) revealed consistent trends, where changes in body weight and BMI trajectories pre- and post-lockdown were observed for women and for individuals < 45 years.

Conclusion: During COVID-19 restrictions, women and young individuals were more likely than other groups to increase BMI category and weight post-lockdown.