The PREBA Study: Effect of Preoperative Weight Loss With a 14-day Low-calorie Diet on Surgical Procedure and Outcomes in Patients Undergoing RYGB Surgery

Ease of the RYGB procedure

Ten aspects of the RYGB procedure will be scored on a 5-point Likert scale. The total score can range from 10 to 50, with 10 being the easiest. The ten aspects include: * Exerting force on instruments (1=very low, 5= very high) * Difficulty of moving the liver (1=very easy, 5=very difficult) * Size of the liver (1=very small, 5= very large) * Size of omentum (1=very small, 5= very large) * Difficulty of approaching pouch (1=very easy, 5=very difficult) * Accessibility of Treitz ligament (1=very easy, 5=very difficult) * Difficulty of creating pouch (1=very easy, 5=very difficult) * Difficulty of measuring small intestine (1=very easy, 5=very difficult) * Difficulty of entero-entero connection (1=very easy, 5=very difficult) * Difficulty of abdominal wall hernia repair (1=very easy, 5=very difficult)

Time frame: surgery

Appearance of the patient's liver

Includes four images of the liver in different stages (1= healthy, 2= fatty liver, 3= fatty liver with inflammation, 4= liver cirrhosis). Surgeons will be asked to choose the image that best matches the appearance of the patient's liver.

Time frame: surgery

Post-operative weight loss

Body weight measurements to assess weight loss after surgery

Time frame: 4 weeks, 3, 6 months and 1, 2, 3, 4, 5 years after surgery