ADA: Belly Fat Loss Best to Halt Diabetes

Sangeeta R. Kashyap, MD, from the Cleveland Clinic, and colleagues reported that, moderately obese patients with uncontrolled diabetes who underwent Roux-en-Y gastric bypass or sleeve gastrectomy had similar weight loss as judged by their body mass index (BMI) at 2 years: 27.4 versus 28.2 kg/m², reported. That means that changes in BMI could not explain the significantly higher number of patients in the bypass group who achieved remission: 33.3% versus 10.5%, Kashyap said here during a late-breaking presentation at the American Diabetes Association meeting.

The answer, she said, was the significantly larger decrease in abdominal fat by those who had bypass surgery compared with sleeve gastrectomy (15.9% versus 10.1%).

The 1-year results of the original STAMPEDE trial, reported at the 2012 American College of Cardiology meeting, showed that either of the two surgical techniques plus optimal medical therapy was better than optimal medical therapy alone at controlling type 2 diabetes. At 12 months, more surgical patients had hemoglobin A1c levels of 6% or less compared with those in the medical therapy arm.

In this substudy, researchers analyzed data from the first 20 patients randomized to each arm (the dropout rate was 10%). Kashyap noted that patients were in their late 40s with a mean BMI of 36. The average duration of diabetes was from 7 to 10 years. Many were on three or more medications and had metabolic syndrome, and more than half were already taking insulin.

Researchers performed a Mixed Meal Tolerance Test to determine the glucose metabolism. At baseline, both surgical groups started at 150 mg/dL and finished at 250 mg/dL. At two years, however, the bypass patients had normal glucose levels at around 85 to 90 mg/dL.

Kashyap commented that, "It was remarkable as it is like seeing a flatline for the heart and then seeing a normal heart wave.

Those in the sleeve gastrectomy arm saw only intermediate glucose effects (150 mg/dL), even though they lost the same amount of weight. And both surgical groups had positive effects for insulin production, but the bypass group had a significant 3.5-fold increase in insulin sensitivity, from 1.5 mg/min at baseline to 5.2 mg/min at 2 years (P<0.001). The sleeve group had a less significant improvement in insulin sensitivity (from 3.9 to 5.7 mg/min, P=0.05).

Beta cell function, measured with the oral disposition index, increased 5.3-fold in the bypass group (P<0.001) and twofold in the sleeve group, the latter being similar to the medical therapy group. Researchers also found that the bypass group had better glucagon-like peptide-1 (GLP-1) and gastric inhibitory polypeptide (GIP) responses. These two hormones are responsible for the secretion of insulin after eating.

Kashyap said that these last two findings are particularly important because insulin production leads to normalization of glycemia. "But it's not just the incretin effect because we saw that effect with the sleeve group whose remission rates were not that great," she said. "We think body composition is the key. The fact that they're melting away truncal fat helps them be more sensitive to insulin and to produce more of it, which is restoring normal glucose metabolism."

• This study found that although two bariatric surgery techniques resulted in similar weight loss, but Roux-en-Y gastric bypass was associated with a higher rate of diabetes remission than sleeve gastrectomy.
• Note that bariatric surgery provided durable glycemic control compared with intensive medical therapy at 2 years.
• This study was published as an abstract and presented at a conference. These data and conclusions should be considered to be preliminary until published in a peer-reviewed journal.

Kashyap SR, et al "STAMPEDE metabolic substudy: Effects of bariatric surgery vs. intensive medical therapy on glycemic control, ß-cell function and body composition in type 2 diabetes" ADA 2012; Abstract 123-LB.