Livingston said he thinks more caution is in order when a very obese person is otherwise healthy.

Along with the risks of surgery, he said, there is still uncertainty about whether it actually lengthens people’s lives. Some studies have suggested it might, but not all.

In a study recently published in the Journal of the American Medical Association, Livingston and his colleagues found no survival advantage among severely obese patients who’d undergone weight-loss surgery versus those who hadn’t.

The study involved 850 U.S. veterans who underwent some form of weight-loss surgery, at an average age of about 50, and more than 41,000 vets who had only non-surgical care. There was no evidence that surgery improved longevity over the next seven years.

“We really don’t even know if there’s a survival benefit,” Livingston said.

That, he added, makes the risks of duodenal switch seem even less worthwhile.

But according to Sovik, duodenal switch might be appropriate for some superobese patients.

In the U.S., he said, about one in three weight-loss surgery candidates have a BMI of 50 or higher. And studies suggest that a sizable percentage of those people will still have a BMI higher than 40 after gastric bypass.

In this study, one-quarter of gastric bypass patients still had a BMI that high two years after surgery - versus none of the duodenal switch patients.

More extensive monitoring after duodenal switch, Sovik noted, can help detect and manage side effects.

He pointed out, though, that larger, longer-term studies are still needed to show whether the extra weight loss with duodenal switch ultimately improves severely obese patients’ health and extends their lives.

SOURCE: Annals of Internal Medicine, online September 6, 2011.