Research in context
Evidence before this study
We searched MEDLINE, Embase, and The Cochrane Library between Jan 1, 2015, and May 15, 2015, for randomised controlled trials comparing bariatric surgery with medical treatment for type 2 diabetes. Our search terms were “bariatric surgery”, “diabetes”, “remission”, “Roux-en-Y gastric bypass” and “bilio-pancreatic diversion”. Randomised trials were included for evidence of glycaemic outcomes; long-term case-control studies were also used to assess evidence of cardiovascular risk and cardiovascular disease reduction after bariatric or metabolic surgery. Only randomised trials with previously published protocols in official sites were considered. Findings from previous trials have shown that bariatric surgery is more effective than conventional treatments for the short-term control of type 2 diabetes. Case-control studies suggest that bariatric surgery might reduce cardiovascular risk and mortality in obese patients with type 2 diabetes.
Added value of this study
Published randomised controlled trials are characterised by a relatively short follow-up time (1–3 years). This is the first report of 5 year outcomes from a trial designed to compare surgery with medical treatment specifically for the treatment of type 2 diabetes. Our findings show that bariatric surgery is more effective than medical treatment for the long-term control of obese patients with type 2 diabetes. Compared with medical treatment, surgery resulted in sustained remission of diabetes in a significant number of patients and in a greater reduction of cardiovascular risk, diabetes-related complications, and medication use, including use of insulin and cardiovascular drugs. Up to 50% of patients who had initial diabetes remission had a relapse of mild hyperglycaemia 5 years after surgery. However, more than 80% of surgically treated patients maintained the American Diabetes Association treatment goal of a glycated haemoglobin A1c concentration less than 7·0% (<53 mmol/mol), despite little or no need for antidiabetic drugs.
Implications of all the available evidence
The available evidence supports consideration of surgery in the treatment algorithm of type 2 diabetes. The ability of surgery to greatly reduce use of diabetes and cardiovascular drugs suggests that surgical treatment of diabetes is a cost-efficient therapeutic approach for this disease. The results of our study also add to a growing body of evidence showing that the gastrointestinal tract is a rational biological target for antidiabetic interventions and support further research into the mechanisms of action of surgery as a way to identify new, less invasive approaches of curative intent.