Effect of RYGB Limb Lengths on HbA1c in Patients with Obesity and Type 2 Diabetes

Roux-en-Y gastric bypass (RYGB) is one of the most commonly performed procedures in metabolic surgery, known for its beneficial effects on type 2 diabetes (T2D). However, the optimal choice of small bowel limb lengths remains a matter of debate. Recent studies suggest that a longer biliopancreatic limb (BPL) could improve T2D more effectively than a longer alimentary limb (AL). The aim of this randomized controlled trial was to compare the effects of a long BPL-RYGB to a long AL-RYGB on T2D in adults with body mass index (BMI) between 27 and 60 kg/m2. 131 patients were randomized 1:1 to long AL-RYGB (150 cm AL/50 cm BPL) or long BPL-RYGB (50 cm AL/150 cm BPL). In patients with BMI > 50 kg/m2, limb lengths were slightly longer. The primary outcome was glycated hemoglobin (HbA1c) after 12 months. Secondary outcomes were T2D remission rate, weight loss, anthropometric measures and blood parameters reflecting glycemic control, dyslipidemia and micronutrient supply. Trial registration number: DRKS00007810 (German Clinical Trials Register Freiburg). Patients in the long BPL-RYGB group showed a -0.33% greater decrease in HbA1c (95% CI [-0.60, -0.06], p = 0.018). Further advantages of long BPL-RYGB were found for improvements in fasting insulin, body weight, BMI and waist-to-hip ratio. No statistically significant differences were observed regarding T2D remission rate, fasting glucose, fasting c-peptide, HOMA-IR index and blood values for dyslipidemia and micronutrients. Patients with obesity and T2D may benefit from a long BPL-RYGB in terms of a greater decrease in HbA1c and weight loss without signals for a greater risk of malnutrition, while diabetes remission rates were comparable between procedures at 12 months. Decrease in HbA1c was greater after long BPL-RYGB than after long AL-RYGB. Body weight and BMI decreased more after long BPL-RYGB than after long-AL RYGB. Long BPL-RYGB did not lead to a greater risk of malnutrition than long AL-RYGB.