Long-Term Metabolic Effects of Gastric Bypass in Obese Patients with Type 2 Diabetes

An effective treatment option for obese patients

By Stacy A. Brethauer, MD; Ali Aminian, MD; and Philip R. Schauer, MD

Advertising Policy

Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services Policy

Although pharmacotherapy is the cornerstone for the management of type 2 diabetes mellitus (T2DM), adequate glycemic control is difficult to achieve in most obese diabetic patients.

Meta-analyses involving more than 100 studies have shown approximately 75 percent remission of T2DM after bariatric surgery, along with the impressive effects on coexisting hypertension and dyslipidemia. Considering the emergence of reliable data, such as the results of the Cleveland Clinic-led STAMPEDE study, and mounting worldwide enthusiasm for bariatric surgeries, the International Diabetes Federation (IDF) and American Diabetes Association (ADA) have recognized bariatric surgery as an effective treatment option for obese patients with T2DM.

Long-term effects of bariatric surgery

In spite of the significant progress in the field, the durability of metabolic effects following bariatric surgery is unknown, as most clinical studies have presented short- and midterm data. In addition, many studies rely on subjective criteria and clinical reporting rather than more stringent objective parameters such as hemoglobin A1c (HbA1c). Moreover, the ultimate effects of metabolic changes after surgery on end-organ complications of T2DM such as diabetic nephropathy have not been fully elucidated.

In order to address some of these unanswered questions, we recently conducted a study at Cleveland Clinic’s Bariatric and Metabolic Institute to evaluate long-term metabolic parameters and clinical outcomes of patients with T2DM who underwent Roux-en-Y gastric bypass (RYGB). We presented the results of our research, which included patients with at least a five-year follow up, at the 133rd Annual Meeting of the American Surgical Association.

Our study (n = 162 with an 80 percent long-term follow-up rate) demonstrated that RYGB is associated with a significant and sustainable remission and improvement of T2DM and other metabolic risk factors in obese patients and should be considered early in the course of the disease. Lasting remission appeared to be related to the duration of T2DM preoperatively, and the extent and durability of weight loss.

Advertising Policy

Study design, remission and recurrence

Study participants had a mean BMI of 48.8 ± 7.6 kg/m2, a median duration of diabetes of five years (range 2–10 years) and a mean preoperative HbA1C of 7.6 ± 1.6 percent. Ninety-five percent of patients were taking diabetes medication at the time of surgery, including insulin in 29 percent. The male to female ratio was 0.35, with a mean age of 49.4 ± 9.5 years.

Complete remission was defined as HbA1C <6 percent and fasting blood glucose (FBG) < 100 mg/dL off diabetic medications; partial remission was an HbA1C of 6 to 6.4 percent and FBG 100–125 mg/dL off medications, and improvement of T2DM was >1 percent reduction in HbA1C or > 25 mg/dL reduction in FBG.

Median follow up

At a median follow up of six years (range 5–9 years), mean total weight loss of 28.1 ± 10.9 percent and excess weight loss of 60.5 ± 24.6 percent were associated with a mean reduction of 1.4 ± 1.6 percent in HbA1C (P < 0.001). At long-term follow up after RYGB, complete remission, partial remission and clinical improvement of T2DM occurred in 31 percent, 30 percent and 31 percent of patients, respectively. Longer duration of T2DM (P < 0.001) and lower excess weight loss (P = 0.04) predicted lack of complete remission.


Long-term recurrence of T2DM after initial remission occurred in 17 percent of the cohort and was associated with longer duration of T2DM (P = 0.03), less excess weight loss (P = 0.02) and weight regain after initial diabetes remission (P = 0.01). Even in this subgroup of patients, glycemic control, metabolic profile and cardiovascular risk factors were significantly improved compared with baseline. For instance, 75 percent of patients with recurrence of T2DM still met the ADA goal of HbA1C < 7 percent at long-term follow up.

Advertising Policy

Long-term follow up

At long-term follow up, patients were taking fewer numbers of diabetic medications (P < 0.001,) including insulin (P < 0.001). In addition, statistically significant improvements in fasting blood glucose, systolic and diastolic  blood pressure, LDL-C, HDL-C and triglycerides were observed after surgery.

A recent national survey found that 52 percent of U.S. patients with T2DM achieve the ADA’s therapeutic goal of HbA1C < 7 percent with medical therapy. In our study, only 41 percent of patients met that goal at baseline since they had higher BMIs and insulin resistance than did average patients with T2DM — but 86 percent met the goal at a median of six years after RYGB. In addition, only 18 percent of patients in the national survey met all three goals of HbA1C, blood pressure and LDL-C control, whereas 28 percent of our cohort met all three goals at long-term follow up.

Diabetic nephropathy

Diabetic nephropathy is considered to be a progressive condition. Generally, the annual transition rate from normoalbuminuria to albuminuria in patients with T2DM is between 2 and 4 percent per year.7 However, we observed a transition rate of < 1 percent per year at long-term follow up in patients with normoalbuminuria at the time of RYGB. In a subgroup of patients with albuminuria at baseline, the condition regressed in 53 percent of patients and remained stable in 47 percent after surgery, without any cases of deterioration.

Demonstrated durable results

The results of this long-term study add to the current body of literature that has demonstrated the benefits of bariatric surgery in short- and mid-term remission of diabetes. Randomized trials are ongoing to evaluate the long-term effects of bariatric surgery compared with medical therapy for diabetes.

Stacy Brethauer, MD, is Associate Director of Cleveland Clinic’s Bariatric and Metabolic Institute and Director of Bariatric Surgery at Cleveland Clinic’s Fairview Hospital in Cleveland, Ohio. Ali Aminian, MD, is a fellow in the Bariatric and Metabolic Institute. Philip Schauer, MD, is Chief of Minimally Invasive Surgery, Professor of Surgery and Director of the Bariatric and Metabolic Institute.