Gender differences in weight gain during lockdown due to COVID-19 pandemic in adolescents with obesity

•Obese adolescents gained weight during lockdown due to pandemic.•Male obese adolescents spent more hours in sedentary activities and therefore were more harmed than females.•Decreased mild physical activity and increased hours spent in sedentary behaviour were the most responsible for weight gain.•Diet was only minimally responsible for weight increase during lockdown.