The number of stomach-shrinking operations for the severely obese has skyrocketed in recent years, partly fueled by extreme makeovers of once-portly celebrities such as weatherman Al Roker, singer Carnie Wilson and “American Idol” judge Randy Jackson.

But these surgeries are riskier than previously thought – especially for the elderly and those suffering from heart disease – with nearly 1 in every 20 Medicare patients dying within the first year after the surgery, a new study shows.

Previous reports from a limited number of surgeons have suggested the risk of death was about 1 in 100 to 1 in 500.

But the new study looked at more than 16,000 patients who received procedures while on Medicare – federal insurance for the elderly and disabled.

“Patients aged 65 or older face a nearly three-fold increase in the risk of early mortality,” said lead researcher Dr. David Flum of the University of Washington.

Flum also found that men are nearly twice as likely to die following such procedures – known as bariatric surgery – as opposed to women. And the surgeon’s experience dramatically affects survival, according to research in today’s Journal of the American Medical Association.

The study also found that more than 5 percent of men and nearly 3 percent of women ages 35 to 44 were dead within a year. And slightly higher rates were found in patients 45 to 54.

“This is very valuable information,” said Dr. Christine Ren, director of the Program for Surgical Weight Loss at NYU Medical Center. “All the numbers that we’ve know before were from selected surgeons or institutions with good results.”

Ren’s center performs the largest number of “gastric banding” operations in the U.S. – a reversible procedure where a band is placed around the stomach to reduce its size.

In Washington State, for example, patients whose surgeons had performed fewer than 20 procedures were nearly five times as likely to die within 30 days after the operation.

“It is clear that this is complicated surgery. It’s also clear that with any complicated surgery the experience of the surgeon is key,” said Rep. Jerrold Nadler (D-N.Y.), who has lost 103 pounds since his high-profile gastric bypass in August 2002.

Despite the greater risk than previously thought, both Ren and Flum agreed that bariatric surgery can be a safe and effective tool for the morbidly obese, who face serious health problems if they don’t lose weight.

A separate study in the same journal showed that the number of bariatric surgeries in the U.S. has ballooned from 13,365 in 1998 to 72,177 in 2002.

The study, led by Dr. Heena Santry of the University of Chicago, projected the number would skyrocket to 218,000 by 2010.

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