People who had weight loss surgery reported greater alcohol use two years after their procedures than in the weeks beforehand, in a new study.

"This is perhaps a risk. I don't think it should deter people from having surgery, but you should be cautious to monitor (alcohol use) after surgery," Alexis Conason, who worked on the study at the New York Obesity Nutrition Research Center at St. Luke's-Roosevelt Hospital Center, told Reuters Health.

Researchers said it's possible some patients may turn to drinking if surgery successfully stops their ability to overeat without addressing their underlying issues. Or, the effects of certain types of stomach-shrinking procedures on alcohol tolerance may influence drinking habits.

Still, the new study can't show whether people were drinking in a dangerous way - and there was no clear increase in drug use or smoking after surgery.

"This does not mean that everyone who has gastric bypass surgery has problems with alcohol or becomes an alcoholic," said Conason.

Her team's study involved 155 people getting gastric bypass or gastric banding surgery, mostly women. Participants started the study with an average body mass index, or BMI, of 46 - equivalent to a five-foot, six-inch person who weighs 285 pounds.

Surgery is typically recommended for people with a BMI of at least 40, or at least 35 if they also have health problems such as diabetes or severe sleep apnea.

Alcohol use dropped immediately following surgery, from 61 percent of people who initially reported drinking to 20 percent at one month post-surgery.

But by three months, drinking rates had started to creep back up. And at two years out, people were drinking significantly more often than before their procedures, according to findings published Monday in the Archives of Surgery.

That was primarily the case for those who had gastric bypass surgery, not banding. On a scale from 0 to 10 of drinking frequency, where 0 represented never, 5 was sometimes and 10 always, gastric bypass patients reported an increase from 1.86 before surgery to 3.08 two years later.

CHANGES IN TOLERANCE

Conason said gastric bypass, in particular, has been shown to drastically lower alcohol tolerance - to the point that some post-surgery patients have a blood alcohol content above the legal driving limit after just one drink. For some, that could make drinking more appealing, she added.

The new findings are "proving more support for the idea that we really need to talk to patients about alcohol use, especially those undergoing (gastric bypass)," said Wendy King, an epidemiologist and weight loss surgery researcher at the University of Pittsburgh, who wasn't part of the study team.

According to the American Society for Metabolic and Bariatric Surgery, about 200,000 people have weight loss surgery every year. The procedures cost about $20,000 each.

Although some researchers have questioned the long-term benefits of surgery, one recent study found three-quarters of people who'd undergone gastric bypass had lost and kept off at least 20 percent of their initial pre-surgery weight six years later (see Reuters Health story of September 18, 2012).

One limitation of the new study is that only one-quarter of the initial participants were still in touch to report their current alcohol and drug use at the two-year mark - so the researchers don't know how everyone else fared.

Psychiatrist Dr. James Mitchell, who has studied alcohol use after weight loss surgery at the University of North Dakota School of Medicine and Health Sciences in Grand Forks, said there's also a need for research going out more than two years - to see if alcohol use keeps increasing.

Researchers said people who've had weight loss surgery should talk with their doctors soon if they notice themselves wanting to drink more.

"The health risks of obesity are such that people with severe obesity should not forgo bariatric surgery because of this," Mitchell, who was not involved in the new study, told Reuters Health.

But he said everyone should be warned about this possibility - and people with a history of alcohol abuse should be particularly careful.

"I don't have the impression (doctors) are talking a tremendous amount about these things," Conason said. "I think we should be. I think we should be educating patients about all the potential risks and benefits."