Patients who had gastric bypass surgery faced double the risk for excessive drinking, according to a study released by in the Journal of the American Medical Association.

The surgery shrinks the stomach’s size and attaches it to a lower portion of the intestine. That limits food intake and the body’s ability to absorb calories. Researchers believe it also changes how the body digests and metabolizes alcohol.

Researchers asked nearly 2,000 women and men who had various kinds of obesity surgery at 10 centers nationwide about their drinking habits one year before their operations, versus one and two years afterward. Most didn’t drink excessively before or after surgery, and increases in drinking didn’t occur until two years post-surgery.