ABSTRACT
Purpose: The coronavirus disease 2019 (COVID-19) pandemic has affected people's daily lives and increased their time spent at home. This study aimed to investigate the changes in lifestyle factors and obesity among Korean adolescents before and during the COVID-19 outbreak. Methods: We used the data of 109,282 adolescents aged 12-18 years, from the Korea Youth Risk Behavior Survey, conducted in 2019 and 2020, before and during the COVID-19 pandemic, respectively. The changes in the prevalence of obesity and lifestyle factors (diet, exercise, sitting time, and sleep duration) were assessed. The adjusted odds ratios (95% confidence interval) [OR (95% CI)] of predictors for obesity were calculated. Results: The prevalence of overweight (10% to 10.5%) and obesity (11.5% to 12.7%) increased significantly, especially among males under 15 years. On the other hand, significant differences were absent among females. The mean body mass index (BMI) z-score increased from 0.28 to 0.39 in males, but decreased from 0.08 to 0.04 in females. Fruit consumption, regular exercise, and average sleep duration decreased, while sitting time increased. After controlling for covariates, a short sleep duration (OR: 1.14) and an increased sitting time (OR: 1.14) were significantly associated with an elevated risk for overweight/ obesity. Conclusion: During the COVID-19 pandemic, the prevalence of obesity and overweight increased, particularly in males, as did unfavorable trends in related lifestyle factors. Sex and age-specific strategies to improve lifestyle factors associated with obesity are needed, especially during the COVID-19 pandemic.