Several prospective trials and metaanalysis have demonstrated the superiority of bariatric surgery on the medical treatment of obesity. The Roux-en-Y Gastric ByPass (RYGBP) procedure has been practiced for more than 30 years, and is the procedure of choice for morbidly obese with metabolic disorders in most of the reference centers. Nevertheless, the RYGBP is a technically demanding procedure with a learning curve of more than 75 cases. The complication rate is around 10% in expert centers.

More recently another procedure has been described which seems as efficient on weight loss and co-morbidities as the RYGBP, with the advantage of being less technically difficult and less morbid, especially for multi-complicated obese and/or the super obese. It consists of a unique gastro-jejunal anastomosis between a long gastric pouch and a jejunal Omega loop. However, this procedure could be at risk of biliary reflux and anastomotic ulcers with dysplastic changes of the gastric and esophageal mucosa. As a result, the Omega loop bypass (OLB) has only been developed by a few teams and remains a controversial subject, particularly as only one monocentric randomized trial has compared it to the RYGBP, which is remains the gold standard. The first litterature results show similar or even better weight loss efficiency than RYGBP with a better feasibility. The early complication rate seems lower, but there are still insufficient data on long term morbidity and biliary reflux consequences.

By performing a randomized and prospective comparison of OLB to RYGBP, the aim of the investigators study is to analyze the weight loss efficiency, the morbidity and mortality, the feasibility, and the quality of life of both techniques, in order to validate the Omega loop bypass as a procedure of choice in bariatric surgery

Hypothesis :

The OLB, while being as efficient as RYGBP on weight loss and metabolic complications, could be less morbid.

Inclusion Criteria:

• Aged between 18 and 65 years old
• Morbid obesity with BMI ≥ 40 kg/m2 or BMI ≥ 35 kg/m2 associated with one or more co-morbidities (type 2 diabetes, arterial hypertension, sleep apnea, dyslipidemia, arthritis)
• Patient who has benefited from an upper GI endoscopy with biopsies
• Patient who has benefited from a pluridisciplinary evaluation, with a favorable opinion for a gastric bypass
• Patient who understands and accepts the need for a long term follow-up
• Patient who agrees to be included in the study and who signs the informed consent form
• Patient affiliated to a healthcare insurance plan

Exclusion Criteria:

• History of esophagitis on upper GI endoscopy (Los Angeles classification)
• Severe gastroesophageal reflux disease (GERD), resistant to medical treatment
• Presence of dysplastic modifications of the gastric mucosa or a history of gastric cancer, on upper gastrointestinal endoscopy.
• Presence of Helicobacter Pylori resistant to medical treatment
• Presence of an unhealed gastro-duodenal ulcer or an ulcer diagnosed less than 2 months previously
• History of previous bariatric surgery (gastric band, sleeve gastrectomy, vertical banded gastroplasty)
• Presence of a severe and evolutive life threatening pathology, unrelated to obesity
• Presence of chronic diarrhea (≥ 3 loose or liquid stools per day, over a period of more than 4 weeks)
• Pregnancy or desire to be pregnant during the study
• Binge eating disorders or other eating disorders according to DSM V criteria
• Mentally unbalanced patients, under supervision or guardianship
• Patient who does not understand French/is unable to give consent
• Patient not affiliated to a French or European healthcare insurance
• Patient who has already been included in a trial which has a conflict of interests with the present study