The aim of this study was to evaluate the impact of coronavirus disease 2019 (COVID-19) lockdown on body mass index (BMI) z-score of adolescents treated for obesity, and to assess the correlation between BMI z-score changes and lifestyle variables.

This cross-sectional study recruited 66 participants aged 11–18 years with overweight or obesity who attended our obesity clinics before and after the lockdown. We assessed demographic and anthropometric characteristics as well as lifestyle variables.

The mean BMI z-score of the participants was stable during this period (p = 0.233). Balanced diet, snacking, and sweet beverage consumption improved in about half of the participants. Having at least one parent at home was associated with a significantly more balanced diet (p = 0.008) and an increase in family activities (p = 0.015). Physical activities decreased (51.5%) and screen time increased for most of the adolescents (86.4%). The BMI z-score decreased significantly when three or more lifestyle habits improved (p<0.001).

This study showed that BMI z-scores were stable for a majority of adolescents treated for obesity during the COVID19 lockdown, along with positive and negative changes on weight-related lifestyle habits. This extraordinary period may have created opportunities for lifestyle modification and has emphasized the importance of family support in the management of obesity in adolescents.