Bariatric Surgery in Diabetes Management

A substantial body of evidence has been accumulating to support the benefits of bariatric surgery in the treatment of metabolic disease.

Evidence from RCTs in patients with T2DM consistently shows superior efficacy for weight loss and improved glycemia with bariatric surgery compared to medical and lifestyle interventions. Studies with 1-5 years of follow-up suggest a mean HbA1c reduction of 2% for surgery vs 0.5% for conventional therapies (P<0.001). In addition, numerous shorter-term RCTs have also found sustained diabetes remission (nondiabetic HbA1c while off all diabetes medications) ranging from 30-63%. Other benefits include decreased mortality, as well as improvements in CVD risk factors, quality of life, micro- and macrovascular complications, cancer, and CVD.¹

Some evidence suggests that these metabolic benefits may be independent of weight loss. For example, a recent study of 31 morbidly obese patients found that a modest amount of surgical weight loss (5-10% of initial weight) was associated with significantly improved cardiometabolic risk factors, as well as 65% remission or clinical improvement rate over a median of six years of follow-up.² Results like these have prompted some experts to propose “metabolic surgery” as a more appropriate term.³ In fact, most worldwide bariatric surgery societies now term these procedures “bariatric/metabolic surgery.”¹

However, a dearth of data exists on long-term outcomes beyond five years after surgery. What data there is suggests that the metabolic benefits of surgery may wane over time, though many patients may continue to benefit.

Some of the longest term outcomes data come from the Swedish Obese Subjects (SOS) study, a prospective cohort study that included 260 standard of care patients with diabetes and 343 surgery patients with diabetes. Results showed that diabetes remission rates in surgery patients were 72.3% at two years, but fell to 30.4% at 15 years. In control patients, these rates were 16.4% and 6.5%, respectively. Compared to usual care, bariatric surgery patients also had significantly fewer microvascular and macrovascular complications.⁴

Another recent study assessed outcomes in 134 patients who underwent vertical sleeve gastrectomy (VSG), and found that few patients achieved long-term remission or “cure” of T2DM. Over a mean follow-up of 6 years, 26% of patients achieved diabetes remission (HbA1c <6.5% off medications), 11% achieved complete remission (HbA1c <6% off medications) , and 3% achieved "cure" (continuous complete remission for ≥5 years). However, 44% experienced long-term T2DM relapse after initial remission, though 67% of those who relapsed were able to reach a HbA1c goal of <7%.⁵

Lack of evidence also precludes establishing a gold standard for bariatric/metabolic surgery. However, a recent expert review found that Roux-en Y gastric bypass (RYGB) may have the most favorable risk-benefit profile in patients with T2DM, compared to other procedures. Studies have also suggested a gradient of efficacy for weight loss and diabetes remission, with greatest efficacy for biliopancreatic diversion (BPD), followed by Roux-en Y gastric bypass (RYGB), then VSG, and with laporoscopic adjustable gastric banding (LAGB) having the least efficacy. Safety also follows a gradient, but in the opposite direction.¹ Longer duration studies are needed, especially for the newest procedure, VSG, which is now the most commonly performed bariatric procedure in the US.⁶

Because diabetes is a progressive disease, delaying intervention may have an impact on long-term health outcomes. Yet no existing guidelines include bariatric surgery in their treatment algorithms. Moreover, only about 1% of morbidly obese surgical candidates actually have surgery.⁷

To draw attention to the situation, six international diabetes organizations recently issued a joint statement at the 2nd Diabetes Surgery Summit (DSS-II), calling for the inclusion of metabolic surgery in diabetes treatment guidelines.¹

Since its release, the DSII guidelines have been formally endorsed by 45 worldwide medical and scientific societies. The recommendations go beyond BMI (currently the sole criteria for selecting patients for bariatric surgery), and include:

• Metabolic surgery, diabetes-specific measures for pre-operative workup and post-operative follow-up for patients with T2DM and class III obesity (BMI≥40 kg/m²) and class II obesity (BMI 35.0-39.9 kg/m²) with inadequate glycemic control despite optimal medical therapy and lifestyle interventions

• Surgery considered in patients with T2DM and BMI 30.0-34.9 kg/m² with inadequately controlled hyperglycemia despite optimal treatment with either oral or injectable medications

• BMI thresholds reduced by 2.5 kg/m² in Asian patients

“Although additional studies are needed to further demonstrate long-term benefits, there is now sufficient clinical and mechanistic evidence to support inclusion of metabolic surgery among antidiabetes interventions for people with T2D and obesity,” the statement asserted.

Take-home Points

• Evidence from RCTs in patients with T2DM consistently shows superior efficacy for weight loss and improved glycemia with bariatric surgery compared to medical and lifestyle interventions. 

• Some evidence suggests that these metabolic benefits may be independent of weight loss.

• Six international diabetes organizations recently issued a joint statement at the 2nd Diabetes Surgery Summit (DSS-II), calling for the inclusion of metabolic/bariatric surgery in diabetes treatment guidelines. Since its release, the DSII guidelines have been formally endorsed by 45 worldwide medical and scientific societies.

• More studies on long-term outcomes beyond 5 years after surgery are needed.

References:

1. Rubino F, et al. Metabolic surgery in the treatment algorithm for type 2 diabetes: a joint statement by international diabetes organizations. Surg Obes Relat Dis. 2016 Jul;12(6):1144-1162.

2. Aminian A, et al. Failed surgical weight loss does not necessarily mean failed metabolic effects. Diabetes Technol Ther. September 2015;17(10) 682-684.

3. Gould JC. Myths surrounding bariatric surgery. JAMA Surg. 2016 Aug 31.

4. Sjöström L, et al. Association of bariatric surgery with long-term remission of type 2 diabetes and with microvascular and macrovascular complications. JAMA. 2014;311:2297-2304.

5. Aminian A, et al. Can sleeve gastrectomy "cure" diabetes? Long-term metabolic effects of sleeve gastrectomy in patients with type 2 diabetes. Ann Surg. 2016 Jul 18.

6. Ponce J, et al. American Society for Metabolic and Bariatric Surgery estimation of bariatric surgery procedures in the United States, 2011-2014. Surg Obes Relat Dis. 2015;11(6):1199-1200.

7. Maciejewski ML, et al. Bariatric surgery and long-term durability of weight loss. JAMA Surg. 2016 Aug 31.