Lockdowns measures including closure of educational institutions due to COVID-19 may affect youth's activity patterns, psychological stress and obesity status. This is the first kind of study in India on the basis of a large number of teenage subjects from the COVID-19 Impact on Lifestyle Changes. Through an online questionnaire, 144 participants from high schools, aged 10-19 years, voluntarily reported their lifestyles and weight, basal metabolic rate (BMI) status in between 19th July to 12th August 2020 (before and after lockdown). Our data suggest that teenagers having prevalence of significant weight (49.6±15.5 to 52.1±15.2 Kgs p <0.001) and BMI (21.0± 1.2 to 22.7±.1.7 p<0.01) gain. Data further showed that this weight gain was for 71.1 % teenagers and BMI 67.2% subjects. Also, significant decreases were seen in the frequency of engaging in active physical activity, and leisure-time walking, while significant increases were observed in the average sedentary time during weekdays and weekends. Our findings would serve as important evidence for making strategies to counteract or reverse the lockdown effects on youths' obesity.