BackgroundThe optimal surgical weight loss procedure for patients with a BMI of 50 kg/m2 or more is uncertain. This study compared distal Roux-en-Y gastric bypass (RYGB) with standard RYGB.MethodsIn this double-blind RCT, patients aged 18–60 years with a BMI of 50–60 kg/m2 were allocated randomly to receive standard (150 cm alimentary, 50 cm biliopancreatic limb) or distal (150 cm common channel, 50 cm biliopancreatic limb) RYGB. The primary outcome (change in BMI at 2 years) has been reported previously. Secondary outcomes 5 years after surgery, such as weight loss, health-related quality of life, and nutritional outcomes are reported.ResultsBetween May 2011 and April 2013, 123 patients were randomized, 113 received an intervention, and 92 attended 5-year follow-up. Mean age was 40 (95 per cent c.i. 38 to 41) years and 73 patients (65 per cent) were women; 57 underwent standard RYGB and 56 distal RYGB. BMI was reduced by 15.1 (95 per cent c.i. 13.9 to 16.2) kg/m2 after standard and 15.7 (14.5 to 16.9) kg/m2 after distal RYGB; the between-group difference was −0.64 (−2.3 to 1.0) kg/m2 (P = 0.447). Total cholesterol, low-density lipoprotein cholesterol, and haemoglobin A1c levels declined more after distal than after standard RYGB. High-density lipoprotein cholesterol levels increased more after standard RYGB. Vitamin A and vitamin D levels were lower after distal RYGB. Changes in bone mineral density, resting metabolic rate, and total energy intake were comparable.ConclusionDistal RYGB did not enable greater weight loss than standard RYGB. Differences in other outcomes favouring distal RYGB may not justify routine use of this procedure in patients with a BMI of 50–60 kg/m2. Registration number: NCT00821197 (http://www.clinicaltrials.gov).Presented in part as abstract to the IFSO (International Federation for the Surgery of Obesity and Metabolic disorders) conference, Madrid, Spain, August 2019.