question: BACKGROUND: The current study aimed to prospectively assess bodyweight change following the implementation of lockdown measures to contain the COVID-19 pandemic in the Netherlands and to explore the potentially moderating role of gender in this association. DESIGN: Using Dutch DNB Household Survey panel data collected between 1993 and 2020, we estimated fixed-effects regression models of bodyweight change. Models were stratified by gender and formal tests of gender differences in coefficient estimates were performed. PARTICIPANTS: 4365 women and 4583 men aged 18-65 were included in the study. The total number of observations was 41 330. OUTCOME MEASURES: The outcome of interest was self-reported bodyweight in kilograms. Additional analyses were performed using body mass index (self-reported weight in kilograms divided by self-reported height in metres squared) as the outcome. RESULTS: The implementation of Dutch lockdown measures in 2020 was associated with bodyweight gain of approximately 800 g in working-age women compared with the 3 prior years. Bodyweight gain in 2020 relative to the prior years was significantly stronger for women than for men (F(4, 8947)=3.9, p<0.01). No evidence of bodyweight gain in working-age men was found. CONCLUSION: Results indicate that bodyweight gain following COVID-19 lockdown measures in the Netherlands was more pronounced among women than among men. Although necessary to contain the COVID-19 pandemic, lockdown measures may contribute to a different public health challenge in the rising prevalence of overweight and obesity.