Bariatric Surgery Has Persistent Benefits for Patients with Type 2 Diabetes

By Sangeeta Kashyap, MD, and Philip Schauer, MD

Type 2 diabetes (T2D) affects more than 25 million individuals in the U.S., but less than 50 percent of patients achieve adequate glycemic control on current pharmacotherapy. Observational studies show improvement in glycemic control and cardiovascular risk factors following bariatric surgery. Short-term (one to two years) randomized controlled trials, including the one-year data from the STAMPEDE (Surgical Therapy and Medications Potentially Eradicate Diabetes Efficiently) trial conducted at Cleveland Clinic, demonstrated remission of T2D following bariatric surgery. However, until now, no long-term (≥ 3 years) randomized controlled trial data existed to compare the durability of effects.

STAMPEDE study design

The trial’s objective was to compare the success rate of an intensive medical therapy (IMT) versus bariatric surgery (either gastric bypass or sleeve gastrectomy) to achieve biochemical remission of T2D in patients with the disease and moderate to severe obesity. The primary end point was the success rate of achieving HBA1c ≤ 6 percent. Secondary end points included change from baseline in fasting plasma glucose (FPG), change in body mass index (BMI) or weight loss, and change in lipids, blood pressure and quality-of-life measures. We also evaluated the effect of surgery on medication usage (diabetic and cardiovascular medications) as well as the rate of adverse events. The Cleveland Clinic Coordinating Center for Clinical Research (C5Research) served as the trial coordinator.

The IMT administered in this study encompassed the American Diabetes Association’s guidelines for standard therapy, but went one step further with the intent to drive HbA1c to 6 percent or less. This was accomplished by incorporating diet and lifestyle counseling and using potent diabetes medications such as insulin sensitizers, GLP-1 agonists, sulfonylureas and insulin. All patients were evaluated and counseled by dietitians and a psychologist in preparation for possible bariatric surgery. They also were instructed in frequent home glucose monitoring and self-titrating their medications.

Our potential participant pool included 218 patients who initially met inclusion criteria and desired to participate, but 68 were ultimately excluded to reach the target enrollment of 150. The inclusion criteria included patients with HbA1c > 7 percent, BMI 27 to 43 and age 20 to 60. Patients were randomized in a 1-to-1-to-1 ratio to the three treatment arms. The population for analysis was 40 IMT, 48 gastric bypass and 49 sleeve gastrectomy. The overall retention rate was 91 percent.

Key findings

The primary end point, HbA1c ≤ 6 percent, was achieved in 5 percent of IMT patients, 37 percent of gastric bypass patients and 24 percent of sleeve gastrectomy patients. Nearly all gastric bypass patients who achieved the primary end-point target did so without requiring any diabetic medications (oral or injectable), while 20 percent of sleeve gastrectomy patients achieved target without medications.

The relative success rate of surgery over medical therapy at reaching biochemical resolution of T2D was quite large and highly significant. Similarly, reduction in FPG favored surgery with 87-point (gastric bypass) and 63-point (sleeve gastrectomy) reductions, compared with 28 points with IMT. Likewise, triglyceride levels decreased 46 percent (gastric bypass) and 32 percent (sleeve gastrectomy) after surgery compared with IMT. There were no differences in LDL cholesterol levels or variations in the percentage change in carotid intimal medial thickness among the three groups. After surgery, patients experienced gradual and steady 9- and 10-point decreases in BMI. While the decrease in BMI was modest in the IMT group, it was remarkable considering the high use of insulin and other drugs likely to cause weight gain. At 36 months, there was greater weight loss in the gastric bypass versus the sleeve gastrectomy group.

Insulin usage decreased by 92 percent in the surgical groups and did not increase in the IMT group, despite poorer glycemic outcomes. Although blood pressure and LDL cholesterol levels did not change significantly in the three groups, there was a significant decrease in the use of cardiovascular medications. At baseline, most patients were taking two, three or more such medications. At 36 months, 68 percent of the gastric bypass patients and 43 percent of the sleeve gastrectomy patients did not take cardiovascular medications any longer. The surgical patients also experienced a significant decrease in dependency on anti-diabetic medications.

Several quality-of-life parameters that our study measured showed that surgery resulted in improved physical function, less body pain and improved overall general health. Increased energy was also noted in the surgical groups. No changes in quality of life were noted with IMT.

As expected, greater gastrointestinal complications occurred in the gastric bypass group, with four reoperations required within the first 12 months. There were a few cases of diabetic complications noted in the surgical groups. Weight gain of greater than 5 percent occurred in 16 percent of the medical therapy group.

Our conclusions

In summary, STAMPEDE found that bariatric surgery was more effective than IMT in achieving glycemic control (HbA1c ≤ 6 percent), with weight loss as the primary determinant of this outcome. Many surgical patients achieved glycemic control without use of any diabetic medications (particularly insulin). Metabolic syndrome components (HDL, triglycerides, glucose, BMI) showed greater improvement after surgery. A marked improvement in quality of life was also demonstrated.

These data are exciting and lead us to conclude that bariatric surgery (gastric bypass or sleeve gastrectomy) should be considered as a treatment option for patients with uncontrolled T2D and moderate to severe obesity (BMI > 30 kg/m2), with results durable through three years of follow-up.

About the authors

Dr. Kashyap is an endocrinologist in the Endocrinology & Metabolism Institute and Associate Professor of Medicine at Cleveland Clinic Lerner College of Medicine. She served as co-principal investigator of the STAMPEDE trial along with Dr. Schauer, Director of the Bariatric and Metabolic Institute, within the Digestive Disease Institute. Reach Dr. Kashap at 216.445.2679 or kashyas@ccf.org and Dr. Schauer at 216.444.4794 or schauep@ccf.org.