Obesity is associated with increased morbidity and mortality. A BMI >40 kg/m 2  shortens life expectancy by about 10 years. The obesity related comorbidities diabetes, hypertension, dyslipidemia and sleep apnea contributes to the increased risk of cardiovascular events. There is also an increased risk of some forms of cancer (e.g. colon, breast, and prostate cancer) as well as mental illness (depression and low self-esteem). Bariatric surgery is indicated for those with a BMI >35 kg/m 2 . Unfortunately, there are an increasing number of patients seeking bariatric surgery who are super obese (BMI >50 kg/m 2 ), a condition more difficult to treat because of insufficient weight loss with standard operations, like the Roux-en-Y Gastric Bypass (RYGB). Therefore some surgeons advocate the Duodenal Switch (DS) in super obese patients, because DS results in greater and more sustained weight loss. However, DS is a technically more challenging operation and is associated with an increased risk of malnutrition and surgical complications. There are also concerns about an excessive loss of fat-free mass during weight loss after RYGB and especially after DS. This thesis focuses on weight-loss, effect on comorbidities, quality of life and complications after DS and RYGB, respectively, with comparisons between the two procedures in patients with super obesity.  DS resulted in a superior weight loss compared to RYGB (paper I, II and III) and body composition after weight loss did not differ compared with non-operated controls with the same BMI after surgery, for neither DS nor RYGB (paper I). Both DS and RYGB resulted in an improved metabolic control (paper II and III), but the effect on diabetes and hypertension was greater and maintained in the long-term after DS (paper III). Both DS and RYGB resulted in an improved physical quality of life, with greater improvements after DS (paper III). However, complications and long-term adverse effects were more common after DS (paper II and IV). In conclusion, the superior weight loss and greater improvements in several obesity-related comorbidities after DS must be weighed against the increased risk of complications and long-term adverse effects compared to RYGB. 
Diss. (sammanfattning) Uppsala : Uppsala universitet, 2019