ABSTRACT
Background The Coronavirus Disease 2019 (COVID-19) epidemic continues to spread worldwide. This study aimed to investigate (1) the change in body mass index (BMI) before and after the COVID-19 outbreak and (2) the impact of behaviours on BMI during the quarantine period. Methods We recruited 197 healthy adults who underwent a physical examination within two months after the Spring Festival holidays of 2018, 2019 and 2020 in Taizhou, China. Of them, 138 respondents answered a questionnaire on lifestyle behaviours during the quarantine period. Univariate analysis and multiple logistic regression models were used to analyse the impact of behaviours during the quarantine period on changes in BMI. Results The average BMI of the population increased from 2018 to 2019 (P<0.05) and then decreased from 2019 to 2020 (P>0.05). The proportion of BMI increase after the COVID-19 outbreak was significantly lower than that in the previous year (41.6% vs. 59.4%, paired χ2=8.151, P=0.002). Young age and living in an urban area were risk factors for a BMI increase in men from 2019 to 2020 (P<0.05), while the habit of eating late-night snacks increased the risk of higher BMI in women (OR=6.11, 95% CI: 1.87–19.98, P<0.05). Conclusions The results of this study demonstrated that there was no significant increase in BMI among the healthy population during the COVID-19 outbreak. Late-night snacking should be discouraged to prevent BMI increases, especially in at-risk women. Level of Evidence: Level III，well-designed cohort