SAN DIEGO—Gastric bypass surgery may improve type 2 diabetes better than a low-calorie diet (LCD), according to data presented at The Endocrine Society’s 92nd Annual Meeting. 

The data come from a study of 14 obese patients with type 2 diabetes. Compared with an LCD, Roux-en Y gastric bypass surgery (RYGB) was associated with greater improvements in insulin sensitivity, adiponectin levels, and beta-cell function, even though weight loss was equivalent with both approaches.

The investigators say the findings reaffirm a beneficial glucostatic effect of RYGB in this patient population. This effect appears to occur independent of acute enteral nutrient passage and fasting gut hormone levels.

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“Our study shows that in the short-term, weight loss by diet alone does not achieve the same improvements in diabetes as gastric bypass surgery,” said investigator Judith Korner, MD, PhD, Assistant Professor of Medicine at Columbia University College of Physicians and Surgeons in New York.

Improved glycemic control after RYGB may be due to changes that occur in food-associated gut hormone signals that occur independent of weight loss, Dr. Korner said. She and her colleagues compared the effects on diabetic adults of a low calorie diet versus RYGB, which is the most common gastric bypass procedure performed in the United States. RYGB decreases the size of the stomach and reroutes the digestive tract to bypass most of the stomach and part of the small intestine. After gastric bypass, many diabetic patients achieve normal or greatly improved blood glucose control, and some may no longer require diabetes medications.

In the new study, the seven subjects received a daily 800-calorie liquid diet and no surgery and seven underwent RYGB. The study ended when both groups lost the same amount of weight: an average of 8% of body weight. 

The surgery patients lost their weight faster than the LCD group (3.5 vs. 8.0 weeks). The surgery patients were able to discontinue all of their diabetes medications by the study’s end, but the dieters were only able to reduce their diabetes medication use by 55%.

The surgery group had significant improvements in insulin sensitivity and beta-cell function. The LCD experienced no significant improvement in insulin sensitivity and their beta-cell function improved to a lesser extent than observed in the surgery patients.

Neither intervention significantly affected fasting gut hormone (gherlin, glucagon-like peptide-1, and peptide YY) levels. Researchers observed a significant increase in adiponectin only in the surgery group.

Dr. Korner said she believes hormonal changes may be responsible for the improvements resulting from RYGB.

She noted that this study only involved a small number of patients, but the dramatic improvements in the surgery patients were striking. All members of the bypass group were able to go off of their diabetes medications, “which is pretty incredible.”

“Even though they weren’t taking the medications anymore it looked like their pancreas was functioning much better,” Dr. Korner said.

Patients with extremely hard to control diabetes should strongly consider gastric bypass surgery, she said.