Blood Glucose

Gastric Surgery and Diabetes: An Overview of the Research

October 20, 2017   /
Elaine M. Hinzey, RD, LDN

Someone in the world dies of diabetes every ten seconds and one in ten health-care dollars goes to diabetes in the United States (US). People with diabetes have health expenditures that are 2.3 times higher than people without the disease. The prevalence of diabetes is 8.9% for the US population as a whole, but is 25% among the morbidly obese. Type 2 diabetes is linked with: cardiovascular disease, stroke, blindness, kidney failure, neuropathy, amputations, impotency, depression, cognitive decline, and mortality risk from certain forms of cancer. Premature death from type 2 diabetes increases by as much as 80%, while life expectancy can be cut by 12 to 14 years.

Gastric surgery improves type 2 diabetes in about 90% of patients by decreasing blood glucose levels, allowing for the lowering of medication dosage and type of medication, and improving complications of diabetes. In 2011, as a result of the 2nd World Congress on Interventional Therapies, the International Diabetes Foundation released a position statement calling for bariatric surgery to be considered earlier in the treatment of diabetes. At this time, it is recommended that gastric surgery be considered for patients with type 2 diabetes and a body mass index (BMI) of 35 or greater. It is also suggested as an alternative treatment for individuals with a BMI between 30 and 35 who cannot achieve adequate blood glucose control with an optimal medical regimen, especially in the presence of other major cardiovascular disease risk factors. 
Related Content
Dietary Guidelines for Post-Bariatric Surgery
Sleeve Gastrectomy (SG) Dietary Protocol after Surgery
Roux-N-Y Gastric Bypass (RNYGB) Dietary Protocol After Surgery

Remission of Type 2 diabetes is believed to occur in 78% of patients immediately following surgery. The American Diabetes Association defines being “cured” as having an A1c of 6% or less, with normal fasting blood glucose (FBG) of 100 milligrams per deciliter (mg/dL) or less, and being completely off diabetes medication for one year. Even in patients who have had their diabetes cured following gastric surgery but then had it reoccur, it generally comes back in a milder form than it was pre-surgery. In addition to having their diabetes go into remission, patients who have gastric surgery also often see a significant decrease in cardiovascular risk factors according to the Framingham Risk Score, and many also see either significant improvement or complete resolution of preexisting nephropathy. 

In a Roux-en-Y gastric bypass (RYGB) surgery, the food is made to bypass the stomach and upper portion of the small intestine. The surgery results in significant weight loss. Remission or improvement in diabetes control typically occurs before significant weight loss is attained; it is likely secondary to a change in hormones produced by the gut. In a sleeve gastrectomy, a large portion of stomach is removed; this procedure also produces weight loss-independent effects on blood glucose control, likely because of similar changes to gut hormones. These changes include an increase in secretion of L cell peptides, such as glucagon-like peptide 1 from enhanced distal-intestinal nutrient delivery. The exclusion of the proximal small intestine from nutrient flow possibly down-regulates unidentified anti-incretin factor(s). Impairment of ghrelin secretion, a change in intestinal nutrient-sensing mechanisms that regulate insulin sensitivity, bile acid perturbations, and alterations in undiscovered gut factors (especially in the duodenum) have all been considered as causes for the vast improvement in blood glucose control following surgical intervention. In some studies, these two surgeries precede similar rates of diabetic remission. The adjustable gastric band procedure involves the placement of a band around the upper portion of the stomach. The rates of remission are lower with this procedure and are believed to occur mainly as a result of weight loss. The duodenal switch procedure is a malabsorptive procedure that is not performed as often as the other surgeries reviewed. It is secondary due to the complexity of the procedure and the relatively high risk of complications. Unfortunately, it is believed to be the most effective in inducing early sustained remission of improvement of diabetes. 

In one study regarding gastric surgery and diabetes, the majority of patients chose the RYGB surgery (162 of 217 patients total), with the remainder choosing gastric banding (n = 32) or sleeve gastrectomy (n = 23). After five to nine years, all patients had a mean excess weight loss of 55% and a drop in A1c to 6.5% from a pre-surgery average of 7.5%, while their FBG dropped from an average of 155.9 to 114.8. About a quarter of patients experienced long-term complete remission, while another 26% had partial remission (defined as having an A1c between 6 and 6.4% with a FBG of 100-125 and one year without necessitating any diabetes medication). Another 34% benefitted from improved long-term control of their diabetes compared to their pre-surgery state. Only 16% experienced no change in their control. Among patients who had the RYBG, 31% experienced complete remission of their diabetes, while 27% were able to continuously sustain remission for more than five years. 

While earlier short-term studies had exclaimed that gastric surgery proffered a remission rate of 72%, it declined to 36% after 10 years. However, even a few years of improvement in symptoms can significantly improve the risk of microvascular and macrovascular endpoints among individuals with diabetes. In fact, 53% of subjects experience a regression of nephropathy and 47% have no further progression of nephropathy (they remain stable). Furthermore, 62% meet blood pressure goals while 72% meet low-density lipoprotein (LDL) cholesterol goals. Most importantly, a sharp decrease in all-cause mortality, cardiovascular death, and first time cardiovascular events after surgery, along with a significant decrease in heart attack risk, occur after 13 years. 

Regarding the dangers of gastric surgery, Buchwald et al. reported on < 30 day and 30 days – 2 year mortality in 85,408 patients in 478 treatment groups in 361 studies from January 1, 1990 to April 30, 2006. Total mortality at < 30 days was 0.28% and was 0.35% between 30 days and two years. The Obesity Surgery Mortality Risk Score assigns one point for each of five preoperative variables: BMI > 50, being male, having hypertension, having a known risk factor for pulmonary embolism, and being 45 years old or older. Those with a score of 0-1 have a low risk, a score of 2-3 have intermediate risk, and a score of 4-5 indicates a high risk of mortality. In one study, a score of 0-1 was associated with a 0.2% risk, a score of 2-3 with a 1.1% risk, and a score of 4-5 with a 2.4% risk. This means that the risk of the highest scoring group is 12 times greater than the risk of the lowest scoring group. 

Restrictive gastric surgery may result in erosion of the band, which causes both abdominal pain and a decrease in efficacy. Aggressive filling of the band may result in slippage. Malabsorptive gastric surgeries can, of course, lead to nutritional deficiency such as protein-calorie malnutrition, calcium and iron deficiencies, or vitamin deficiency. These deficiencies might result from anorexia, inadequate supplementation, prolonged vomiting, stricture formation, or failure of absorption. Wernicke’s encephalopathy and beriberi have been reported as resulting from thiamine deficiency caused by prolonged vomiting following malabsorptive gastric surgery. Peripheral neuropathy and spinal cord lesions from B12 and folate deficiency have also been reported. 

Among individuals who undergo laparoscopic bypass, the risk of wound problems hover around 2.98% and the risk of incisional hernias is roughly 0.47%. Among people who elect gastric bypass surgery, 2.1% will suffer from small bowel obstruction and 0.7% with anastomotic stenosis, while 0.6% may experience gastrointestinal (GI) hemorrhage, 1.2% may have a leak, < 1% will develop a pulmonary embolism, and 0.1-0.3% will develop pneumonia. Major weight loss by any means increases the risk of cholelithiasis. 

Even taking the risk associated with these surgeries into consideration, it is believed that as many as 14,310 diabetes-related deaths might be prevented by bariatric surgery over five years if the number of surgeries increases to a million annually. 

The DiaRem score, which is based on four simple clinical measures, can help to identify which people with type 2 diabetes are most likely to be “cured” following gastric surgery. The clinical measures for consideration are age, A1c, insulin utilization, and use of other antiglycemic medications.

< 40 0
40-49 1
50-59 2
> 60 3
HbA1c (%)
< 6.5 0
6.5-6.9 2
7-8.9 4
> 9 6
Noninsulin Antiglycemic Drug Use
Metformin 0
Other noninsulin medication 3
Insulin Use
Use of insulin 10

Among 407 patients who had RYGB, half of the 100 with the best score (score of 0-2) experienced remission, but none of the 33 with the worst score (score of 18-22) were cured. In this case, “cured” was defined as an A1c of < 5.7% for at least five years with no antiglycemic medication use in the past year. Eighty two percent of those with DiaRem of 0-2 attained prolonged partial remission of diabetes, while none of the patients with a score of 18-22 experienced the same. 

References and recommended reading

Andrei Keidar A. Bariatric surgery for type 2 diabetes reversal: the risks. Diabetes Care. 2011;34(Suppl 2):S361-S266. doi:10.2337/dc11-s254.

Busko M. Simple score predicts bariatric-surgery-related diabetes cure. Medscape website. Published April 21, 2016. Accessed May 26, 2016. 

Nainggolan L. Gastric bypass ‘cures’ diabetes in almost a third of patients. Medscape website. Published September 19, 2013. Accessed May 26, 2016. 

Kelland K. Specialists call for gastric surgery to be standard diabetes treatment. Scientific American website. Published May 24, 2016. Accessed May 26, 2016.

Surgery for diabetes. American Society for Metabolic and Bariatric Surgery website. Accessed May 26, 2016.


Reviewed and Updated March 22, 2017