Impact of Lifestyle Changes on Body Weight Gain During Nationwide Lockdown Due to COVID-19 Pandemic

<b>Background:</b> During the coronavirus disease 2019 (COVID-19) pandemic, people in Japan were urged to stay at home as much as possible, and this resulted in significant changes in lifestyle behavior. The new lifestyle included factors affecting both energy intake and energy consumption, and it is now thought that weight gain during the lockdown was the result of complex effects. The aim of this study was to determine the relationships among lifestyle habits, laboratory data, and body weight gain during the lockdown using medical check-up data. <b>Methods:</b> A total of 3789 individuals who had undergone consecutive medical check-ups during the period from 2018 to 2020 were included in this study. Participants whose body weight had increased by 5% or more were divided into two groups: a before-lockdown group (participants who had gained weight between 2018 and 2019) and an after-lockdown group (participants who had gained weight between 2019 and 2020). Physical measurements, laboratory data, and answers to six questions about lifestyle habits, for which information was obtained from the records from medical check-ups, were compared in the two groups. <b>Results:</b> There was no significant difference between the distribution of weight changes in 2018-2019 before the lockdown and the distribution of weight changes in 2019-2020 after the lockdown. The before-lockdown and after-lockdown groups both included about 7% of the total participants (279 and 273 participants, respectively). Diastolic blood pressure and levels of AST, ALT, and LDL-C were significantly higher in the after-lockdown group than in the before-lockdown group. The percentages of participants with alcohol consumption and exercise habits were significantly higher in the after-lockdown group than in the before-lockdown group, and an analysis by gender showed that the differences were significant for women but not for men. <b>Conclusions:</b> The distributions of weight changes before and during the COVID-19 pandemic were similar. Exercise habits and alcohol consumption might have been unique factors causing weight gain during the COVID-19 pandemic, particularly in women. Our findings suggest that the impact of behavioral restrictions and lifestyle changes during a pandemic may be different in men and women.