Gastric bypass surgery to treat obesity lowers the risk of Heart disease even more than previously believed, U.S. researchers reported on Thursday.

Patients who underwent the surgery showed improved levels of three new measures of Heart disease risk - C-reactive protein, lipoprotein A and homocysteine, the team at Stanford University School of Medicine found.

They measured these proteins, as well as cholesterol levels, in 371 patients before surgery and again a year later and found improvements to normal range in all of them.

“Medication with statins - the most effective non-surgical treatment available - lowers C-reactive protein by about 16 percent,” Dr. John Morton, assistant professor of surgery at Stanford, said in a statement.

“But we found that gastric bypass lowered it by 50 percent. That’s a pretty significant improvement over what’s been considered state-of-the-art therapy.”

Morton’s colleague, Dr. Brandon Williams, presented the findings to a meeting of the American Society for Bariatric Surgery in Orlando.

Gastric bypass surgery makes the stomach smaller so patients can eat less, and cuts out a long stretch of small intestine so fewer nutrients are absorbed .

The Society estimates that 141,000 of the procedures were done in 2004. It is not risk-free - about 2 percent of patients die.

“This operation is reserved for morbidly obese people, not the pleasantly plump,” Morton said in a statement.

“The risk of premature death for the morbidly obese is about three times the risk of the general population.”

The Society says 15 million people in the United States are morbidly obese, as measured by body mass index (BMI), which is a person’s weight in kilograms divided by height in meters squared.

A BMI of 30 is obese and one of 40 qualifies as morbidly obese. Someone 5 feet 8 inches tall and weighing 265 pounds (120 kg) would have a BMI of 40.

The improvements in heart disease risk factors extended beyond what would have been expected due to weight loss alone. “We’re not sure why, but the process of bypassing the stomach might induce some changes in both lipid and inflammatory metabolism,” Morton said.

“I think our findings show that this is not in any sense a cosmetic procedure - that it really does benefit the health of these patients,” Williams said.