Abstract Background One-Anastomosis Gastric Bypass (OAGB) is a widely adopted metabolic surgery for individuals with severe obesity and related comorbidities. However, postoperative protein deficiency is a common concern due to reduced intake, malabsorption, vomiting, and food intolerances. Many patients fail to meet recommended protein intake during the rapid weight loss phase, increasing the risk of fat-free mass loss. Whey protein, known for its high biological value and rich content of branched-chain amino acids, has been shown to enhance muscle protein synthesis and may help preserve lean body mass. While the use of OAGB is expanding, evidence on the role of whey protein supplementation post-OAGB remains limited. Objective To assess the effects of daily whey protein supplementation on weight loss, body composition, and nutritional outcomes in patients undergoing OAGB. Methods In this double-blind, randomized controlled trial, 78 patients (BMI 40–50 kg/m²; 89.7%female) undergoing primary OAGB were randomized to either a whey protein or placebo group. The intervention group received a daily 200 ml clear Iso whey protein shake containing 22.6 g of whey protein for three months postoperatively, in addition to standard dietary guidance. The control group received an isocaloric clear placebo shake containing maltodextrin. Both groups received identical dietary counselling. Body composition (via BIA), anthropometric measures, and biochemical profiles were assessed at baseline, 1 month, and 3 months post-surgery. Results Both groups showed significant reductions in fat mass, and visceral fat, and improvements in glycaemic and lipid profiles. However, fat-free mass, total body water, and muscle mass were significantly better preserved in the whey protein group compared to the placebo group (P 0.05). No significant differences were observed between groups in total weight loss (TWL%) or nutritional markers such as serum albumin. Conclusion Early postoperative Iso whey protein supplementation following OAGB may help preserve lean body mass and support improved body composition without affecting total weight loss or serum nutritional biomarkers. This strategy appears safe, tolerable, and clinically beneficial.
Farsi et al. (Thu,) studied this question.