Type 2 diabetes mellitus responds to weight loss surgery

Type 2 diabetes mellitus (T2DM) is a metabolic condition with close links to weight gain. Since weight loss is a proven way to control T2DM, it is to be expected that surgeries to achieve weight loss should result in better regulation of blood glucose levels.

A new study published in the journal JAMA Surgery in March 2020 shows that this does happen in a significant percentage of patients who have undergone these procedures when assessed five years after surgery.

Image Credit: Fuss Sergey / Shutterstock
Image Credit: Fuss Sergey / Shutterstock

The study

The researchers used data from the National Patient-Centered Clinical Research Network (PCORnet), which contains electronic health information from a nationwide patient database, to compare the control levels of T2DM between patients who had undergone two major procedures for weight loss, namely, the Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG).

The researchers analyzed data on approximately 10,000 patients who were operated on at 34 different centers. They looked at the type of procedure performed, as well as the levels of postoperative hemoglobin A1C.

The findings

Most patients were female and white, with a mean age of about 50 years. The mean HbA1C was 7.2% before surgery, and patients were on 1.7 diabetes drugs, on average. Approximately 64% had undergone RYGB, and 36% had an SG.

Medical conditions associated with excessive weight were common. For instance, sleep apnea was present in 57% and 50% of patients before RYGB and SG, respectively. Gastroesophageal reflux disorder (GERD) was a complication in 42% and 36% of these patients, respectively, with non-alcoholic liver disease (NAFLD) occurring in 30% and 21%, respectively.

Following the procedure, the weight loss was more with RYGB at 29% compared to 23% with SG after one year and at five years – this translates into a difference of about 10 kg at five years. While some of this weight was typically gained back, RYGB and SG patients continued to have a 24% and 16% lower steady weight compared to their weight at the time of the surgery.

The adjusted analysis shows that over 8 of every 10 patients in the study had reasonable control of T2DM over the five years after the surgery. That is, they were able to maintain an HbA1C level below 6.5% without antidiabetic medication for six months or longer. The remission rate was 10% higher in patients who had RYGB than in SG patients. About 59% and 56% of patients with these procedures were in T2DM remission at one year, and 86% vs. 84% at five years.

However, one-third of patients in remission after RYGB and approximately 40% of those in remission after SG relapsed to suboptimal glucose control at five years. At the 5-year mark, only half of RYGB patients and a third of SG patients continued to have good control of their T2DM. Overall, the HbA1C levels were 0.45% lower in patients who had undergone RYGB vs. SG.


It is possible that relying on indirect information can introduce inaccurate diagnostic and medication data, as well as confounding factors that are not recorded.


Bariatric or weight loss surgery can cause significant enhancement of blood sugar control in T2DM, but with much difference across populations and procedures. Weight loss was greater, the remission rate for T2DM higher, the relapse rate lower, and the long-term HbA1C control better after RYGB compared to SG.

The current study covers a large population and shows a high rate of remission of T2DM after weight-loss surgery performed in a real-life situation rather than an experimental setup. However, the high rate of relapse needs to be investigated to identify the factors responsible for it.

Compared to remission rates in trials where the patients were subjected to strict and intensive lifestyle modifications, the patients in the current study had higher remission rates.

According to the American Diabetes Association, weight loss surgery is recommended as an option for the management of diabetic patients with obesity but is seldom used. Only less than one in a hundred patients with obesity above class I (BMI 35 or above), and even fewer diabetic patients because they typically have a BMI of 34 or less, thus not fulfilling the criteria for this surgery.

Moreover, weight loss surgery is typically not covered by universal insurance plans. The experts conclude, “Continued advocacy for bariatric surgery coverage, including expansion for patients with T2DM and class 1 obesity, will be critical. All patients deserve access to the most effective, evidence-based obesity and diabetes treatments.” The knowledge of these findings can help patients make better and more informed decisions as to the type of surgery.

Journal reference:

McTigue KM, Wellman R, Nauman E, et al. Comparing the 5-Year Diabetes Outcomes of Sleeve Gastrectomy and Gastric Bypass: The National Patient-Centered Clinical Research Network (PCORNet) Bariatric Study. JAMA Surg. Published online March 04, 2020. doi:10.1001/jamasurg.2020.0087

Dr. Liji Thomas

Written by

Dr. Liji Thomas

Dr. Liji Thomas is an OB-GYN, who graduated from the Government Medical College, University of Calicut, Kerala, in 2001. Liji practiced as a full-time consultant in obstetrics/gynecology in a private hospital for a few years following her graduation. She has counseled hundreds of patients facing issues from pregnancy-related problems and infertility, and has been in charge of over 2,000 deliveries, striving always to achieve a normal delivery rather than operative.


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