Background <p>Gastric bypass surgery is an efficient surgical intervention for the treatment of obese patients. The procedure can be performed either laparoscopically or robotic assisted. To simplify the intracorporeal handling of the suture material in a bi- or tri-dimensional plane, a new generation of sutures, named barbed sutures, has been developed recently and is being used for different indications. Barbed sutures allow knotless slippage-resistant suturing due to the self-anchoring elements distributed along the thread length and therefore obviate the need for assistance. Their safety and efficacy have been demonstrated in several meta-analyses and systematic reviews. In the present study, the clinical performance of a new unidirectional barbed suture material, which differs in regard to its configuration from other barbed suture materials, is analysed and compared to a conventional suture material in robotic-assisted gastric bypass surgery to treat morbid obesity.</p> Methods <p>The study will be performed as an industry-sponsored, mono-centre, randomized, active-controlled, two-arm, parallel-group, superiority trial. A total of 150 patients will be randomly allocated to both suture types in a 1:1 ratio. The suture material will be used to construct the gastro-jejunal anastomosis as well as the jejuno-jejunal anastomosis. The time needed to create both anastomoses is the primary endpoint. Intraoperative handling of both suture materials, patient satisfaction, pain, and complications occurring during the study will serve as secondary outcomes. Furthermore, the difference in quality of life using two different questionnaires (EQ5D5L and Bariatric Analysis and Reporting Outcome System (BAROS)) will be assessed preoperatively and postoperatively (30 days and 12 months) and will be compared between the suture groups as well as over time. The EQ-5D-5L questionnaire consists of five dimensions (mobility, self-care, usual activities, pain or discomfort, anxiety or depression) and a visual analogue scale (VAS) to record the patient’s health status. The BAROS evaluates three sub-categories: The percentage of excess weight loss, the changes in medical conditions, and quality of life, leading to three individual sub-scores, which are added to the final total score defining the failure or success of treatment. The follow-up period is 1 year after surgery.</p> Discussion <p>To our knowledge, the BARGASTRO study will be the largest randomized controlled trial investigating a barbed suture versus a conventional one in robotic-assisted gastric bypass surgery to treat obese patients. The study will provide and report clinical data on evidence level Ib.</p> Trial registration <p>NCT05433688. Registered on 12 Oct. 2022</p>