In 2003, a study of more than 1,000 patients who underwent gastric bypass found that one-third of those with diabetes at baseline had normal blood sugars after their surgery and didn’t need medication when they were discharged from their surgical hospitalization. This finding sparked further exploration into the effects of gastric bypass surgery on weight-independent, antidiabetes mechanisms.
Testing a New Population
In Diabetes Care, my colleagues and I had a study published that explored the use of Roux-en-Y gastric bypass (RYGB) as a primary modality to treat type 2 diabetes in patients for whom weight loss was not the primary objective. When we began the study, clinical observations had suggested that diabetes remits in about 80% of patients who undergo gastric bypass. What we didn’t know was the durability of that effect or what the outcomes would be in patients who weren’t severely obese. In our analysis, we selected 66 consecutive patients with type 2 diabetes who were mildly obese (BMI between 30 kg/m2 and 35 kg/m2) to undergo RYGB. These patients were prospectively studied for up to 6 years. At baseline, they had an average A1C of 9.7% despite being on insulin or at least two diabetes medications.
At 6 months after RYGB, the average A1C level decreased to 6.5% and continued to decrease to 6.1% at 6 years, with 100% follow-up in this cohort. At the latest follow-up, 88% of patients had achieved diabetes remission, which was defined as having an A1C of 6.5% or less and being off all diabetes medications. We also found that â-cells were nearly five times more sensitive to blood sugar, on average, at latest follow-up when compared with baseline measures. No relationship was observed between change in BMI and change in fasting blood sugar levels, A1C levels, or insulin secretion at 3 and 6 months and at 1, 2, 3, and 4 years. Participants also had improvements in hypertension and dyslipidemia that yielded 50% to 85% reductions in predicted 10-year cardiovascular disease risks of fatal and nonfatal coronary heart disease and stroke.
One of the big objectives at the onset of our study was to determine if gastric bypass was as safe in patients with mild obesity as it is for those with severe obesity. There were zero mortalities in our study, compared with a 0.2% rate that has been observed in studies of severely obese patients undergoing RYGB. Additionally, no member of our study group experienced major complications. The rate for minor complications was 15%, but this was deemed acceptable considering that the expected rate ranges between 10% and 15% for severely obese patients.
Revisiting NIH Guidelines
The current NIH guidelines for using gastric bypass surgery recommend that this operation only be performed in patients with a BMI above 40 kg/m2, or above 30 kg/m2 with serious comorbidities. Considering the findings from our investigation, policy makers should think about revisiting these guidelines and possibly changing them accordingly. Our research adds to the growing body of data that indicate the benefits of gastric bypass beyond the severely obese.
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