BACKGROUND: The COVID-19 lockdown may have negatively impacted the treatment of obesity. This study aimed to assess the effect of COVID-19 lockdown in patients with obesity treated with intensive residential cognitive behavioral therapy (CBT-OB). METHODS: This retrospective case-control study analyzed 129 patients with severe obesity who experienced COVID-19 lockdown in the 6 months after discharge from intensive residential CBT-OB, comparing their outcomes on weight loss, binge-eating episodes, and general health status with those in a sample of patients matched by gender, age, and body mass index given the same treatment before the COVID-19 outbreak as control. Patients were assessed at baseline and by phone interview 6-month follow-up. RESULTS: Both groups had lost more than 9% of their baseline bodyweight and reported a significant decrease in binge-eating episodes and similar general health status at 6-month follow-up. However, control patients achieved a significantly greater weight loss than those who experienced lockdown, although half of lockdown patients reported persisting with CBT-OB procedures after their discharge. CONCLUSION: Patients with obesity treated with CBT-OB and exposed to COVID-19 lockdown, despite achieving lower weight loss than non-exposed patients, had a healthy weight loss at 6-month follow-up and comparable reduction in binge-eating behaviors.