Background: The coronavirus disease-2019 (COVID-19) has resulted in nationwide lockdowns, cessation of school and work, and social distancing. Reducing the negative impacts, such as weight-gain, has garnered global attention.Methods: In this dual-center retrospective observational study of 12,889 students (aged 18-20), who performed a national student physical fitness battery between December 1, 2019, to January 20, 2020, and completed a follow-up online questionnaire beginning on May 1, 2020, and ending on May 23, 2020, and examined the associations between weight-gain and COVID-19 induced stress, depression and self-reported physical activity, dietary habits and sedentary time. Results: Participants gained an average of 2.6 kg (95% CI: 2.0 to 3.2 kg) for males and 2.1 kg (1.9 to 2.4 kg) for females. An increase in overweight and obese individuals according to Asian cut-off points as a demographic percentage by 4.5% and 2.7% and 4.8% and 3.4% in males and females respectively (P<0.001). Weight change was associated with sedentary time, COVID-19 induced stress, and depression score. Conclusion: These findings suggest that limiting sedentary time during lockdowns and strategies aimed t improve lifestyle habits and psychological health may be warranted to mitigate weight-gain during the pandemic.Registration: Registered with ChiCTR, registration no.: ChiCTR2000033514

The COVID-19 (coronavirus disease-19) has resulted in nationwide lockdowns, cessation of school and work, and social distancing. Reducing the negative impacts, such as weight-gain, has garnered global attention. In this dual-center prospective cohort study of 12,889 students, we assessed weight-gain in a youth during the 4-month COVID-19 lockdown, and examined the associations between weight-gain and COVID-19 induced stress, depression and self-reported physical activity, dietary habits and sedentary time. Participants gained an average of 2.6 kg (95% CI: 2.0 to 3.2 kg) for males and 2.1 kg (1.9 to 2.4 kg) for females. An increase in overweight and obese individuals as a demographic percentage by 4.5% and 2.7% and 4.8% and 3.4% in males and females respectively (P<0.001). Weight change was independently associated with severe COVID-19 induced stress, sedentary time, and depression score. Techniques to relieve COVID-19 induced stress, reduce sedentary time through increased physical activity, and improve dietary habits in youth may be warranted to help prevent and/or reverse weight-gain associated with the lockdown period of COVID-19.Registration: Registered with ChiCTR, registration no.: ChiCTR2000033514