Metabolic surgery for the treatment of type 2 diabetes in obese individuals

Abstract

Several bariatric operations originally designed to promote weight loss have been found to powerfully treat type 2 diabetes, causing remission in most cases, through diverse mechanisms additional to the secondary consequences of weight loss. These observations have prompted consideration of such operations as 'metabolic surgery', used expressly to treat diabetes, including among patients who are only mildly obese or merely overweight. Large, long-term observational studies consistently demonstrate that bariatric/metabolic surgery is associated with reductions in all cardiovascular risk factors, actual cardiovascular events, microvascular diabetes complications, cancer and death. Numerous recent randomised clinical trials, directly comparing various surgical vs non-surgical interventions for diabetes, uniformly demonstrate the former to be superior for improvements in all glycaemic variables, as well as other metabolic endpoints. These benefits are similar among individuals with type 2 diabetes and a preoperative BMI of 30-35 kg/m² compared with traditional bariatric surgery patients with a BMI >35 kg/m². The safety profiles of modern laparoscopic bariatric/metabolic operations are similar to those of elective laparoscopic hysterectomy and knee arthroplasty. However, more evidence regarding the risks, benefits and costs of surgery is needed from very long-term (>5 year) randomised clinical trials powered to observe 'hard' clinical endpoints following the operations most commonly used today. Given the efficacy, safety and cost-effectiveness of metabolic surgery, the second Diabetes Surgery Summit (DSS-II) consensus conference recently placed surgery squarely within the overall diabetes treatment algorithm, recommending consideration of this approach for patients with inadequately controlled diabetes and a BMI as low as 30 kg/m², or 27.5 kg/m² for Asian individuals. These new guidelines have been formally ratified by 53 leading diabetes and surgery societies worldwide. Given this broad level of endorsement, we feel that the DSS-II recommendations should now replace the outdated National Institutes of Health (NIH) suggestions that have governed bariatric surgery practice and insurance compensation worldwide since 1991.

Keywords: Bariatric surgery; Biliopancreatic diversion; Diabetes Surgery Summit; Gastric bypass; Ghrelin; Glucagon-like peptide-1; Laparoscopic adjustable gastric banding; Metabolic surgery; Review; Vertical sleeve gastrectomy.

Fig. 1

Odds of diabetes remission or glycaemic control in all 11 randomised clinical trials of surgery vs medical/lifestyle care for type 2 diabetes. Forest plot of Peto ORs of primary outcomes (main glycaemic endpoints [GE], i.e. either diabetes remission or glycaemic control, depending on the trial) from each of the 11 published randomised clinical trials directly comparing bariatric/metabolic surgery vs medical/lifestyle treatments for diabetes. Data are arranged in order of ascending mean baseline BMI of each study group. The orange dotted line demarcates trials performed on cohorts with an average starting BMI either <35 kg/m² or ≥35 kg/m². Column 1 depicts study duration and HbA_1c endpoint thresholds (in square brackets). Here, ‘off meds’ refers to a threshold achieved off all diabetes medicines, whereas otherwise the endpoints represent thresholds attained with or without such agents. ORs (shown with 95% CI) >1 indicate a positive effect of surgery compared with medical/lifestyle treatment. The pooled Peto OR (95% CI) for all data was calculated using a fixed-effects model. mo, months; SG, sleeve gastrectomy. © 2016 by the ADA [14]. Adapted with permission from the ADA

Fig. 2

DSS-II: surgery in the type 2 diabetes treatment algorithm. Algorithm for the treatment of type 2 diabetes, including the option of bariatric/metabolic surgery, as recommended by DSS-II voting delegates. Rx, treatment. © 2016 by the ADA [2]. Adapted with permission from the ADA