The classic RYGB is in most patients with a BMI ≥45 technically not feasible. Two alternatives are the Extended Pouch Gastric Bypass and the One Anastomosis gastric bypass. In this single blinded randomized controlled trial the investigators aim to establish which technique leads to more weightloss in bariatric patients with a BMI ≥45.

Obesity is of increasing incidence worldwide. With it come major social-economical, medical and psychological problems which lead to high healthcare costs. Bariatric surgery is the most efficient treatment for morbid obesity, with the Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (GS) being the most performed.

The RYGB is preferable since this technique seems to lead to more reduction of obesity related comorbidities (DM2) and more weightloss in the long term. However, the RYGB is technically less feasible in patients with a BMI ≥45, due to less intra-abdominal space (excess fat in mesenterium) to connect the anastomosis tension-free.

An alternative for the RYGB are the Extended Pouch gastric bypass (EPGB) and the One-Anastomosis gastric bypass (OAGB). These techniques both involve an extended pouch which makes it easier to connect the anastomosis tension-free.

Furthermore, the extended pouch in the EPGB and OAGB could provide slower passage of food and stretches less on the longer term than the 'normal size'pouch in the RYGB, possibly leading to more weightloss (1,2).

Previous studies comparing the EPGB and RYGB showed more weightloss in patient undergoing EPGB and less weight gain in the long term (3). Other studies comparing the OAGB, RYGB and GS showed non-inferiority or even superiority of the OAGB for weightloss and remission of obesity related comorbidities as diabetes mellitus type 2 (DM2) and obstructive sleep apnea syndrome (OSAS) (4,5,6,7).

Theoretically the OAGB is a simpler procedure which reduces the risk of internal herniation and anastomotic leakage, since only one anastomosis is made (6,8) Only performing one anastomosis leads to less operating time, shorter time of anesthesia, and less usage of staple material. Which possibly makes this a safer and cheaper procedure.

Both techniques, EPGB and OAGB, seem to be adequate alternatives for the RYGB in patients with a BMI of 45 or higher. As of yet, the two techniques haven't been compared one to one. In this single blinded randomized controlled trial the investigators aim to establish which technique leads to more weightloss in bariatric patients with a BMI ≥45.

Inclusion criteria:

• BMI≥45
• Bariatric guidelines Fried
• Age 18-65
• Dedication to guided preoperative program
• Intention to follow full postoperative program

Exclusion criteria:

• Secondary bariatric procedure
• Medical(-related) cause for morbid obesity or fast weight gain (e.g. Cushing or medication related)
• Inflammatory Bowel Disease (M. Crohn or Colitis Ulcerosa)
• Renal function disorder (MDRD <30) or liver disease
• Anticipated absence of yearly medical follow up
• Does not speak Dutch language
• Pregnancy

No sharing.

Patients will be randomized single blinded for one of two study arms/procedures. 3 years post-operative unblinding will be done for participants wishing this.