Trends in weight gain recorded in English primary care before and during the Coronavirus-19 pandemic: an observational cohort study using the OpenSAFELY platform

Background We investigated which clinical and sociodemographic characteristics were associated with unhealthy patterns of weight gain amongst adults living in England during the pandemic. Methods With the approval of NHS England we conducted an observational cohort study of Body Mass Index (BMI) changes between March 2015 and March 2022 using the OpenSAFELY-TPP platform. We estimated individual rates of weight gain before and during the pandemic, and identified individuals with rapid weight gain (>0·5kg/m 2 /year) in each period. We also estimated the change in rate of weight gain between the prepandemic and pandemic period and defined extreme-accelerators as the ten percent of individuals with the greatest increase (>1·84kg/m 2 /year). We estimated associations with these outcomes using multivariate logistic regression. Findings We extracted data on 17,742,365 adults (50·1% female, 76·1% White British). Median BMI increased from 27·8kg/m 2 [IQR:24·3-32·1] in 2019 (March 2019 to February 2020) to 28·0kg/m 2 [24·4-32·6] in 2021. Rapid pandemic weight gain (n=3,214,155) was associated with female sex (male vs female: aOR 0·76 [95%CI:0·76-0·76]); younger age (50-59-years vs 18–29-years: aOR 0·60 [0·60-0·61]); White British ethnicity (Black Caribbean vs White British: aOR 0·91 [0·89-0·94]); deprivation (least-deprived-IMD-quintile vs most-deprived: aOR 0·77 [0·77-0·78]); and long-term conditions, of which mental health conditions had the greatest effect (e.g. depression (aOR 1·18[1·17-1·18])). Similar characteristics increased risk of extreme acceleration (n=2,768,695). Interpretation We found female sex, younger age, deprivation and mental health conditions increased risk of unhealthy patterns of pandemic weight gain. This highlights the need to incorporate sociodemographic, physical, and mental health characteristics when formulating post-pandemic research, policies, and interventions targeting BMI. Funding NIHR