The finding underscores the value of the surgery for extremely overweight people whose obesity puts them in danger of heart attack, stroke and other cardiovascular illness, say the researchers.

Gastric bypass surgery, the most common form of weight-loss surgery, reduces the stomach's size to limit the amount of food intake and bypasses more than 35 inches of the approximately 20-foot-long small intestine, which cuts down on nutrient absorption.

The researchers measured biochemical cardiovascular risk factors in 371 patients before surgery and again 12 months after gastric bypass surgery, adding three new tests to the standard panel of cholesterol and triglyceride assays. They saw improvements in all cardiac risk factors, with the most significant improvements for triglycerides and one of the new tests: C-reactive protein.

Lowers C-Reactive Protein by 50%

"Medication with statins -- the most effective non-surgical treatment available -- lowers C-reactive protein by about 16 percent," said senior author John Morton, MD, assistant professor of surgery at the Stanford School of Medicine and director of bariatric surgery at Stanford Hospital.

"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," Dr. Morton added.

Lead author Brandon Williams, MD, a general surgery resident, will present the study's findings today at the annual scientific meeting of the American Society for Bariatric Surgery.

Life-Saving Operation for Morbidly Obese

The number of gastric bypass surgeries has shot up in recent years, increasing from 29,000 procedures in 1999 to about 141,000 in 2004, according to the bariatric surgery society. The procedure poses about a 2 percent risk of mortality and requires lifelong changes in eating habits -- but it's a life-saving operation for most morbidly obese individuals, Morton said.

"This operation is reserved for morbidly obese people, not the pleasantly plump," Morton said. "Being morbidly obese carries a pretty significant risk of premature death, in large part because of heart disease. The risk of premature death for the morbidly obese is about three times the risk of the general population."

Though for most obese people, the most compelling reasons to lose weight have to do with improvements in lifestyle, the health benefits are tremendous, Williams said. He expects that the new study will encourage physicians to discuss the surgery with obese patients who are at risk of heart disease. And he hopes that the findings will push insurance companies that deny coverage for the procedure to change their policies.

More than 15 million people in the United States are morbidly obese, as measured by body mass index, which is a person's weight in kilograms divided by height in meters squared. A BMI over 40 qualifies as morbidly obese, according to National Institutes of Health guidelines for bariatric surgery.

So, for example, a person whose height is 5 feet 8 inches and weight is 265 pounds would have a BMI of 40 and would be considered morbidly obese.

Beyond Weight Loss

Morton, Williams and Stanford colleagues knew from earlier studies by others that gastric bypass lowered many risk factors for heart disease but no large-scale studies had investigated the effects of the surgery on all three newer heart-disease markers: C-reactive protein, lipoprotein A and homocysteine, Williams said. They set out to study the effects and found improvements across the board.

"All of the values improved to where they were no longer in the abnormal range. In other words, they normalized," Morton said.

The most significant decrease in risk was seen in C-reactive protein levels, which dropped from 10 mg/L to 3 mg/L. According to the Centers for Disease Control, C-reactive protein levels greater than 3 mg/L indicate high risk for cardiovascular disease.

Interestingly, the improvements went 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.

The lowering of cardiac risk factors was especially compelling given the patients' dire condition before their surgery, Williams said. "The study showed that these patients were at great risk of heart disease before their surgery. Their risk factors were even higher than we had expected," he 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 added.