CHICAGO, Oct. 3 (Xinhua) -- A study from Washington University School of Medicine in St. Louis shows that a less common weight-loss procedure called biliopancreatic diversion appears to be more effective at eliminating diabetes not just because of greater weight loss but because the procedure itself seems to make patients more sensitive to insulin.

The researchers followed 24 patients, half of whom had the most frequently performed Roux-en-Y gastric bypass surgery and the other half rarely performed biliopancreatic diversion.

The gastric bypass group in the study had average body mass indexes (BMI) of 48. Those who had biliopancreatic diversion had average BMI of 56.

A person's BMI is calculated using weight and height. A higher BMI increases the risk of health problems related to weight; a BMI of 30 is considered obese.

While the patients had obesity, none had been diagnosed with type 2 diabetes. The study was structured this way because the researchers wanted to independently measure the insulin sensitivity after a meal, without potential complications caused by diabetes medications.

The surgeries were performed at Catholic University in Rome.

After surgery and a 20 percent loss of body weight, the study patients' metabolic reactions to meals were measured, with close attention paid to their glucose levels, sensitivity to insulin and how much insulin they secreted after eating.

The researchers found no difference in the benefit of surgery-induced weight loss to patients' pancreatic function, in terms of insulin secretion, but patients who received biliopancreatic diversion surgery were found to be more sensitive to insulin.

"This study demonstrates that biliopancreatic diversion has unique, beneficial effects on insulin action, independent of any weight loss," said senior author Samuel Klein, director of Washington University's Center for Human Nutrition.

"This study demonstrates additional metabolic benefits from biliopancreatic diversion, compared to Roux-en-Y gastric bypass," Klein said. "But the type of bariatric surgery performed on any individual patient depends on many considerations, including an assessment of the effectiveness and safety of the procedure, patient preference, and the surgeon's experience."

Roux-en-Y gastric bypass provides considerable benefits in helping people lose weight and in treating type 2 diabetes but does not have the weight-loss-independent benefits on insulin sensitivity of biliopancreatic diversion, Klein added.

In the United States, some 228,000 bariatric surgical procedures were performed in 2017. Fewer than 3 percent were biliopancreatic diversion.

The findings were published on the online version of journal Cell Metabolism on Thursday.