People who had weight-loss surgery using the so-called duodenal switch technique lost more of their extra body weight and had better control of diabetes and high blood pressure than those who had a more traditional gastric bypass, according to a new study.

But the duodenal switch also came with extra blood loss and longer hospital stays, and more patients who had the procedure ended up with nutrient deficiencies.

During a gastric bypass, a surgeon shrinks the size of the stomach by making its upper portion into a smaller pouch and connecting that directly to the small intestine.

In comparison, a duodenal switch involves "bypassing" much of the small intestine, where nutrients are absorbed. That puts patients who've had the surgery at greater risk of malnutrition and vitamin deficiencies in the future - so they have to watch their diet extra closely, researchers said.

Because of those long-term risks and concern about complications during the more difficult surgery, the duodenal switch "hasn't caught on in the United States as much," according to Dr. Alec Beekley, a bariatric surgeon from Thomas Jefferson University Hospitals in Philadelphia.

Still, "I think it's a viable alternative for some patients," Beekley, who wrote a commentary published with the study in the Archives of Surgery, told Reuters Health.

"The advocates say, yes, there is potential for nutritional problems and vitamin deficiencies over the long run, but they're manageable if you properly select patients" and follow them carefully, he added.

According to data from the American Society for Metabolic and Bariatric Surgery, about 220,000 people had any type of weight loss surgery in 2009.

For the new study, researchers from Madigan Army Medical Center at Fort Lewis, Washington tracked close to 79,000 procedures done between 2007 and 2010 - 98 percent of them gastric bypasses and two percent duodenal switches.

Going into the surgery, duodenal switch patients tended to have more underlying diseases and were also heavier, with an average body mass index of 52, compared to 48 in gastric bypass patients.

For a five-foot, six-inch woman, that translates to 322 pounds versus about 298 pounds.

Duodenal switch procedures lasted longer than gastric bypass surgeries: three hours, 11 minutes compared to one hour, 54 minutes, on average. The less-common procedure also resulted in more than three times as much blood loss.

Over the long run, one out of every 24 duodenal switch patients developed a major nutritional deficiency, compared to one in every 48 people who'd had a gastric bypass.

But people also tended to lose slightly more of their excess weight after a duodenal switch than a gastric bypass, and duodenal switch patients ended up with better control of their diabetes, high blood pressure and sleep apnea.

More challenging and 'drastic'

The duodenal switch is the most technically difficult weight loss procedure for surgeons to perform and is also considered the most "drastic," according to Dr. Matthew Martin, the trauma medical director at Madigan and senior author of the new study.

Because weight loss from the duodenal switch appears to hold up better than after a gastric bypass, Martin thinks the more challenging surgery will likely become increasingly popular in the U.S. over the next decade.

Beekley said it's hard to tell which patients having weight loss surgery are going to be the most dedicated to taking the necessary vitamins and watching their diet closely after surgery to prevent nutrition problems.

But he said the duodenal switch may work best for some of the most overweight people with a range of chronic diseases who seem dedicated to sticking closely to doctors' orders after their procedure.

Or the duodenal switch could be a back-up option for people who originally choose a third type of weight loss surgery, called sleeve gastrectomy, but don't lose enough weight, Beekley said.

Martin told Reuters Health in an email that patients considering surgery should discuss all their options with an experienced bariatric surgeon.

"If they have a very large amount of weight to lose and/or have severe medical co-morbidities such as diabetes, then the duodenal switch is an excellent option and will have a higher chance of curing their obesity and diabetes than even a gastric bypass," he said.

"But each patient has a different balance of potential risks versus potential benefits, and these must be weighed carefully when making such a critical decision."