BACKGROUND: To compare efficacy and safety of a manual-based low-level psychological intervention with treatment as usual (weight loss treatment). METHODS: A two-armed randomized controlled trial without blinding and computer-based stratified block randomization included adolescents and young adults (14.0-24.9 years) with a BMI ≥ 30 kg/m2 at five German university hospitals. Primary outcomes were adherence (participation rate ≥ 5/6 sessions) and quality of life (DISABKIDS-37) 6 months after randomization. Secondary outcomes included depression, self-esteem, and perceived stress scores. RESULTS: Of 397 screened adolescents, 119 (mean BMI 40.4 ± 7.0 kg/m2, 49.6% female) were randomized to the manual-based low-level intervention (n = 59) or treatment as usual (n = 60). We observed no group difference for adherence (absolute risk reduction 0.4%, 95% CI -14.7% to 15.5%; p = 1.0) or health-related quality of life (score difference 8.1, 95% CI -2.1 to 18.3; p = 0.11). Among all secondary outcomes, we detected explorative evidence for an effect on the DISABKIDS-37 'social exclusion' subscale (score difference 15.5; 95% CI 1.6-29.4; p = 0.03). 18/19 adverse events occurred in 26 participants, none were classified as serious. CONCLUSION: Adherence to a coping-oriented intervention was comparable to weight loss treatment, although it was weak in both interventions. Psychological interventions may help to overcome social isolation; further confirmation is required.