Background COVID-19-related restrictions impacted weight and weight-related factors during the initial months of the pandemic. However, longitudinal analyses are scarce.
Methods An online, longitudinal study was conducted among self-selected UK adults (n=1,818), involving three surveys during 2020 (May-June, August-September, November-December), covering height, weight and sociodemographic, COVID-19-related and behavioural measures. Data were analysed using generalised estimating equations.
Results Self-reported average weight and body mass index (BMI) significantly increased from May-June to August-September (74.95kg to 75.33kg, 26.22kg/m2 to 26.36kg/m2, both p<0.001), and then significantly decreased to November-December (to 75.06kg, 26.27kg/m2, both p<0.01), comparable to May-June levels (p=0.274/0.204). However, there was great interindividual variation, with 37.0%/26.7% reporting an increase and 34.5%/26.3% reporting a decrease in weight/BMI greater than 0.5kg/0.5kg/m2, respectively from May-June to November-December. The average weight/BMI increase was 3.64kg (95% confidence interval: 3.32,3.97)/1.64kg/m2 (1.49,1.79), and the average weight/BMI decrease was 3.59kg (3.34,3.85)/1.53kg/m2 (1.42,1.63). In fully adjusted models, increase in weight/BMI across surveys was significantly negatively associated with initial BMI, and positively associated with monthly high fat, salt and sugar (HFSS) snacks intake and alcohol consumption, and for BMI only, older age. However, associations were time-varying, such that lower initial BMI, higher HFSS snacks intake and high-risk alcohol consumption were associated with maintenance of increased weight/BMI from August-September to November-December.
Conclusion The average weight/BMI of UK adults increased during the early pandemic months, before returning to baseline levels in November-December 2020. However, this masks substantial interindividual variation in weight/BMI trajectories, indicating vulnerabilities associated with changes in food and alcohol consumption throughout the pandemic.