Introduction: The worldwide prevalence of obesity and type 2 diabetes (T2D) constitutes an epidemic that is a threat to public health. Bariatric surgery, including Roux en-Y gastric bypass (RYGB), is currently the most effective treatment to induce long-term weight loss and remission of co-morbid conditions. Surgery, however, comes with an added risk of complications, highlighting the need to understand the comparative effectiveness and risks of surgical versus conventional approaches to the treatment of obesity and T2D.

Areas covered: Positive and negative outcomes of RYGB surgery in patients with T2D are assessed, with a primary focus on RYGB surgery versus standard non-surgical treatment of obese patients with T2D in randomized clinical trials or high-quality observational cohorts.

Searches were conducted in the PubMed database up to 11 April 2019 for relevant studies.

Expert opinion: High-level evidence reveals that RYGB ameliorates the clinical manifestations of T2D to a significantly higher degree than medical therapy. Postoperative incidence of beneficial effects and complications, however, differ across subgroups of patients with different preoperative characteristics. Key knowledge gaps, particularly on long-term complications, microvascular- and macrovascular events, and mortality should be addressed, so treatment with RYGB can be applied in an individualized approach to maximize benefits and minimize complications.