BACKGROUND: Prevalence rates of overweight and obesity have increased in German children and adolescents in the last three decades. Adolescents with extreme obesity represent a distinct risk group. On the basis of data obtained by the German Child and Youth Survey (KiGGS) and the German district military offices we estimate that the group of extremely obese adolescents (BMI >= 35 kg/m2) currently encompasses approximately 200.000 adolescents aged 14 to 21 yrs. Conventional approaches focusing on weight reduction have largely proven futile for them. In addition, only a small percentage of adolescents with extreme obesity seek actively treatment for obesity while contributing disproportionately strong to health care costs. Because of somatic and psychiatric co-morbidities and social problems adolescents with extreme obesity require special attention within the medical care system.We have initiated the project "Medical and psychosocial implications of adolescents with extreme obesity - acceptance and effects of structured care, short: 'Youths with Extreme Obesity Study (YES)'", which aims at improving the medical care and social support structures for youths with extreme obesity in Germany. METHODS: We focus on identification of these subjects (baseline examination) and their acceptance of diagnostic and subsequent treatment procedures. In a randomized controlled trial (RCT) we will investigate the effectiveness of a low key group intervention not focusing on weight loss but aimed at the provision of obesity related information, alleviation of social isolation, school and vocational integration and improvement of self-esteem in comparison to a control group treated in a conventional way with focus on weight loss. Interested individuals who fulfill current recommended criteria for weight loss surgery will be provided with a structured preparation and follow-up programs. All subjects will be monitored within a long-term observational study to elucidate medical and psychosocial outcomes. Our aim is to evaluate realistic treatment options. Therefore inclusion and exclusion criteria are minimized.We will recruit adolescents (age range 14--21 years) with extreme obesity (BMI >= 35 kg/m2) (extreme group) within 24 months (120 per centre, 5 centres) as well as obese adolescents being at risk for developing extreme obesity (BMI >= 30 -- 34.9 kg/m2) (at risk group). Follow-up evalutations will be performed biannually after inclusion and is planned to be extended in case of additional funding. In sum, we aim at establishing evaluated health care structures for extremely obese adolescents. DISCUSSION: The results of YES will be of importance for a frequently neglected group of individuals, for whom current medicine has little to offer in terms of structured access to empirically evaluated therapeutic programs. Thus, the results will be both a help for the adolescents within the study and for others in the future given that the trial will lead to a positive finding. Moreover, it will help practitioners and therapists to deal with this neglected group of individuals.Trial registrationProject registration numbers for each subproject: 1.) ClinicalTrials.gov: NCT01625325, NCT01703273, NCT01662271, NCT01632098; 2.) Germanctr.de: DRKS00004172, DRKS00004195, DRKS00004198, DRKS00004197.