The purpose is to study whether the positive effects from obesity surgery in adults also can be achieved when adolescent subjects are operated.

Our hypothesis is that the effects concerning weight loss, health improvement and improved quality of life will be as good in adolescents as in adults.

Severe obesity in the adolescence is a major concern since there is a constant rise in prevalence worldwide. There is a need of effective tools to treat those patients since the natural course with conservative treatment is very pessimistic. I. e. most of the subjects having a BMI >40kg/m2 in the adolescence will remain morbidly obese also in their adult life.

The three largest centres in Sweden treating obese children (Stockholm, Gothenburg and Malmö) will offer patients fulfilling the inclusion criteria to be operated with laparoscopic gastric bypass. If not willing to be operated they could join the study as a control case.

Subjects will be investigated at the baseline concerning physical health status and existence of medical risk factors but also regarding their quality of life, eating habits and physical activity. They will subsequently be follow over a ten year period regarding these variables.

Inclusion Criteria:

• BMI >40 kg/m2 or BMI>35 with comorbidity
• Pass psychological evaluation
• Puberty status Tanner 4-5
• At least one year with active conservative treatment that failed

Exclusion Criteria:

• Lack of compliance
• Specific obesity syndrome as Praeder Willis
• Obesity due to brain injury
• Severe general disease
• Specific genetic defect (MC4R, Leptin deficiency)