Obesity surgery may significantly increase the risk of alcohol abuse, according to a new study.

Researchers found that patients who had undergone gastric bypass surgery had double the risk for excessive drinking two years after the operation, compared with patients who had a less dramatic weight-loss operation.

The study consisted of 1,945 participants undergoing weight-loss surgery at one of 10 hospitals across the U.S.

Study participants had completed the Alcohol Use Disorders Identification (AUDIT) test, which detects symptoms of alcohol use disorders, like symptoms of alcohol abuse or dependence, commonly known as alcoholism.   

Participants were categorized as having an alcohol use disorder if they had at least one symptom of alcohol dependence, like not being able to stop drinking after the first drink, or alcohol-related harm like not being able to remember or if their total AUDIT score was at least 8 out of 40.

Researchers found that overall prevalence of alcohol use disorder in patients who had the Roux-en-Y (RYGB) gastric bypass surgery, which reduces the size of the stomach and shortens the intestine, limiting food intake and the body's ability to absorb calories, increased from 7 percent before surgery to 10.7 percent in the second year after surgery, a relative increase of more than 50 percent compared to pre-surgical rates.

Some people who have had gastric bypass surgery say that they feel the effects of alcohol much more quickly, after drinking less than before their surgery, and the latest findings suggest that the changes in the way the body digests and metabolizes alcohol after the surgery may lead to problem drinking.

About 70 percent of the participants in the study were gastric bypass patients, and 25 percent of the participants had laparoscopic adjustable gastric banding surgery, which makes the stomach smaller with a band, and about 5 percent of the patients had other, less common weight loss surgeries.

While almost 11 percent or 103 of 996 bypass patients, had drinking problems two years after surgery, about 5 percent of patients who had stomach-banding obesity surgery drank excessively two years later, similar to the pre-surgery numbers, which were similar to pre-surgery numbers.

Lead author and assistant professor Dr. Wendy King of the University of Pittsburgh Graduate School of Public Health found that 1 in 8 study participants had reported having at least three drinks on a typical drinking day the second year after surgery.

"This is concerning, given the negative impact heavy drinking may have on vitamin and mineral status, liver function and weight loss," King said in a statement.

Researchers noted that regular alcohol use before surgery, which equated to at least two drinks per week, was also associated to a higher risk of having an alcohol problem after surgery. Patients who reported less social support, or who reported using recreational drugs and smoking before surgery were also more likely to report symptoms of AUD after surgery.

Men and younger adults were also more likely to develop drinking problems after surgery, as well as people with depressive symptoms, mental health treatment, and binge eating prior to surgery.

"The study results suggest that clinicians should be aware of the importance of monitoring for signs and symptoms of AUD and consider counseling after bariatric surgery" Dr. Mary Horlick, project scientist for LABS at the NIH's National Institute of Diabetes and Digestive and Kidney Diseases said in a statement.

Traditionally, bariatric surgery was reserved for people with a body mass index (BMI) of 40 or higher or patients with a BMI of 35 or higher with a serious health problem.

There has also been accumulating evidence that supports the surgery's effectiveness in helping people lose weight, reverse risk factors for heart disease and in some cases reverse type 2 diabetes, leading doctors to consider it as therapy for people with less severe obesity.

"These findings show that there is much more to learn about bariatric surgery and how it influences a patient's health and well-being" said NIDDK Director Dr. Griffin P. Rodgers. "It is important that patients and their doctors be fully aware of short- and long-term benefits and risks of bariatric surgery. We hope the LABS results will help researchers identify clinical questions that require further research, including better understanding of the risk of AUD."

The findings were published online Monday in the Journal of the American Medical Association.