Weight loss surgery may cut the risk of heart disease by nearly half among the extremely obese.

A new study shows that extremely obese people who had weight loss surgery had less than half the risk of heart disease following surgery and were also less likely to require heart surgery to unclog blocked arteries than those who did not have the surgery.

In medical terms, extreme obesity is known as morbid obesity and is defined as having a body mass index (BMI, a ratio of weight in relation to height) of 40 or higher.

Morbid obesity is associated with a number of heath risks, including an increased risk of heart disease, type 2 diabetes, high blood pressure, and others.

“No other treatment has been shown to have this much impact on preventing or reducing heart disease in patients with morbid obesity,” says researcher Nicolas V. Christou, MD, PhD, of McGill University Health Center in Montreal, in a news release.

The results of the study were presented this week at the annual meeting of the American Society for Bariatric Surgery in San Francisco.

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In the study, researchers compared the risk of heart disease and related complications between 1986 and 2002 among a group of 1,035 morbidly obese patients who had weight loss surgery with more than 5,700 who did not have the surgery.

The most common form of weight loss surgery is called a gastric bypass, in which the size of the stomach is reduced and a section of the small intestine is bypassed in order to reduce the amount of food and calories a person is able to consume and digest to encourage rapid weight loss.

Overall, those who had weight loss surgery lost about 67 percent of their excess body weight after the surgery.

The results of the study showed that morbidly obese people who had weight loss surgery dramatically reduced their risk of heart disease and other heart-related complications compared with those who did not have the surgery.

For example, weight loss surgery patients:

Required less than half the number of heart surgeries, such as coronary bypass and procedures, such as angioplasty. Were 5 times less likely to experience an irregular heartbeat that may lead to cardiac arrest or death. Reduced their risk of other heart-related problems, such as fluid in the lungs, which can lead to respiratory failure by more than half. Had nearly half the rate of severe heart pain (angina) caused by inadequate blood flow to the heart.

Researchers say the risks and benefits of weight loss surgery should be discussed on an individual basis, but these results show that one of the benefits of the procedure is a reduced risk of heart disease.

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By Jennifer Warner, reviewed by Louise Chang, MD

SOURCES: Christou, N. “The Impact of Bariatric Surgery on Cardiovascular Morbidity,” presented at the 23rd Annual Meeting of the American Society for Bariatric Surgery, San Francisco, June 26- July 1, 2006. News release, American Society for Bariatric Society.