When bariatric surgery first came about, its intended purpose was to treat severe obesity by creating a bypass of the small intestine. We now know that this method of bypassing parts of the gut can be beneficial for other diseases, including type 2 diabetes (T2DM). Despite the array of agents that are currently available to manage diabetes, including insulin, oral agents, and diet and exercise regimens, we see a limited amount of success with these therapies, with a large number of diabetic patients suffering from blindness, amputation, renal failure, heart attack, and the many other complications that come with diabetes. In an article in Diabetic Technology & Therapeutics, EC Moore and WJ Pories considered the benefits of bariatric surgery and asked why it is not being used more in patients with T2DM.
One of the studies reviewed in this article looked at the impact of gastric bypass surgery on patients with severe and longstanding diabetes and low BMIs (30-35 kg/m2). The study followed 66 patients over a period of 5 years and looked at safety and resolution of diabetes as their primary outcomes. They found that long-term remission of diabetes occurred in 88% of the patients, and that HbA1c levels fell from 9.7%±1.5% at the beginning of the study to 5.9% ± 0.1% at the completion of the study. The amount of weight lost was not found to correlate with diabetes remission, which suggests that there was an alternative mechanism for diabetes resolution in these patients. An increase in C-peptide after surgery was also observed, indicating a possible increase in β-cell function. The findings of this study support the conclusion that gastric bypass can be a safe and effective way to treat diabetes in patients with lower BMIs.
Another study of 120 participants compared the effectiveness of intensive medical management vs. gastric bypass surgery in treating diabetes. The primary endpoints were to reduce A1c <7%, lower LDL cholesterol levels <100mg/dl, and have a systolic BP
A third study looked to identify factors that would predict nonresponders and responders to surgery preoperatively so that only patients that would get the most benefit from the procedure would undergo surgery. Of 82 patients studied, diabetes did not improve in 17 patients. Longer duration of diabetes, higher A1c levels, age, and preoperative use of multiple medications were predictive of responsiveness to surgery.
Bariatric surgery was also found to prevent the onset of T2DM in obese patients not currently diagnosed with T2DM. This finding came from a study in which 1,658 Swedish patients were followed for 15 years after receiving bariatric surgery and compared with obese match-controlled patients not receiving surgery for the incidence of T2DM. T2DM developed in 392 patients in the nonsurgical group and in 110 patients in the gastric bypass group, leading to the conclusion that bariatric surgery seems to prevent onset of T2DM in obese patients.
The studies mentioned here suggest that bariatric surgery can not only be used to induce remission of T2DM, but can also be used to reduce onset in the first place. A survey of physicians has uncovered a relative reluctance to refer T2DM patients with lower BMI for bariatric surgery, which hinders further studying of the benefits of bariatric surgery in this group.
Medicare has, however, approved reimbursement for bariatric surgery in patients with a BMI ≥40 and in those with BMI ≥35 with comorbidities such as diabetes or HTN based on evidence of its benefits. BMI, however, is not an accurate measure of obesity as it does not account for the patient’s fitness and muscularity. BMI is also unigender and therefore does not account for the differences seen between men and women. Asians and African Americans are also more likely to develop diabetes and HTN at a lower BMI than Caucasians. The standards for surgery eligibility therefore need to be adjusted to account for these differences.
- Bariatric surgery has been seen to induce remission of T2DM in obese patients and patients with lower BMI and to prevent onset of T2DM in obese patients.
- Factors such as age, duration of diabetes, higher A1c, and number of medications used to treat diabetes have been found to be predictive of a patient’s response to bariatric surgery.
Moore EC, Pories WJ. “Metabolic Surgery Is No Longer Just Bariatric Surgery” Diabetic Technology & Therapeutics.2014; 16:78-84.