On the heels of a five-year boom in weight-loss surgeries, researchers are observing an unusual phenomenon: Some patients stop overeating -- but wind up acquiring new compulsive disorders such as alcoholism, gambling addiction or compulsive shopping.

Awareness of the issue is just beginning to surface. Some bariatric-surgery centers say they are starting to counsel patients about the issue. Substance-abuse centers, including the Betty Ford Center in Rancho Mirage, Calif., say they are seeing more bariatric-surgery patients checking in for help with new addictions. And alcohol use has become a topic of discussion on bariatric-surgery-support sites, such as Weight Loss Surgery Center, wlscenter.com.

Some psychologists describe it as a type of "addiction transfer," an outcome of substance-abuse treatment whereby patients swap one compulsive behavior for another. At the Betty Ford Center, about 25 percent of alcoholics who relapse switch to a new drug, such as opiates.

The behavior has long been explained as a psychological phenomenon as patients seek new strategies for filling an inner void. But as substance-abuse experts learn to decode the brain's addiction pathways, some researchers are coming to believe that swapping behaviors may have a neurological basis. A new wave of research suggests that the biochemical causes of compulsive eating are extremely similar to those underlying other self-destructive addictions, such as alcohol or cocaine addiction. Alcohol use in particular is a concern for bariatric patients because some versions of the surgery can change the way patients metabolize alcohol, making it far more powerful.

Exploring the overlaps between compulsive eating and other addictions is a growing focus at the National Institute on Drug Abuse, which spent $1.4 million on obesity research last year. Researchers at NIDA hope to piggyback on the drug industry's extensive research on obesity in an effort to find new compounds that might treat multiple types of impulse-control disorders at once.

"The potential is extraordinary," says Nora Volkow, NIDA director. "A drug that could condition craving behavior -- whether it's for chocolate or cocaine -- would be a gigantic market."

Dozens of clinical trials on addiction treatments are under way at the National Institutes of Health. Topiramate, an epilepsy drug marketed by Ortho-McNeil Neurologics under the name Topamax, is currently being studied for binge eating, alcohol dependence, cocaine addiction and compulsive gambling.

Bupropian, marketed by GlaxoSmithKline as the antidepressant Wellbutrin and the smoking-cessation drug Zyban, is currently being studied as a treatment for gambling, obesity, nicotine dependence and alcoholism. And Rimonabant, made by Sanofi-Aventis is being reviewed by the Food and Drug Administration as a treatment for obesity and associated health problems, but it is also being studied as a treatment for alcoholism.

Estimates on the prevalence of new addictions after weight-loss surgery vary widely. Philip Schauer, director of bariatric surgery at the Cleveland Clinic and current president of the American Society for Bariatric Surgery, estimates that only about 5 percent of bariatric-surgery patients develop a new compulsive behavior after surgery, such as alcoholism, compulsive shopping or smoking. He adds there is no evidence that the new addictions have any direct link to the surgery.

At U.S. Bariatric, a weight-loss surgery center with offices in Orlando and Fort Lauderdale, Fla., therapists estimate that roughly 20 percent of patients acquire new addictive behaviors. Melodie Moorehead, a psychologist who spoke at a session during the American Society for Bariatric Surgery Association annual meeting last month, cited preliminary data suggesting that roughly 30 percent of bariatric-surgery patients struggle with new addictions after surgery. But she says the issue requires further study.

One possible reason for the disparity in estimates is that alcohol problems can surface several years after the surgery, when surgeons are no longer tracking patients as closely. And some patients may not see a link between their drinking and the surgery, or report their problem to a surgeon. Roughly 140,000 bariatric surgeries are performed in this country each year.

Some bariatric doctors dismiss the issue as pure coincidence. "People don't become alcoholics as a side effect of the surgery," says Neil Hutcher, past president of the American Society for Bariatric Surgery. "They become alcoholics for the same reasons anyone becomes an alcoholic. The surgery is not a cure-all for everything transpiring in the patient's life."

For a variety of reasons -- including the fact that alcohol is high in calories -- bariatric-surgery patients are often advised not to drink alcohol for the first six months to a year after surgery. In addition, most bariatric centers screen patients for heavy alcohol use, and exclude patients who exhibit signs of alcohol dependence.

"The surgery creates profound changes in people, both physical and mental," says Dr. Schauer. "Even though they're good changes, they could ignite problems in people with active substance-abuse problems."

Gastric bypass surgery, which accounts for 75 percent of all bariatric surgeries in the U.S., involves sectioning off a small portion of the stomach into a pouch that bypasses the first part of the small intestine. As a result, alcohol passes rapidly into the intestine where it is quickly absorbed into the bloodstream. "You shorten the time to the brain so much that if you liked alcohol before, you'll love it now," says Mark Gold, professor of psychiatry and neuroscience at the University of Florida College of Medicine. (Lap-band procedures, which account for 20 percent of U.S. weight-loss surgeries, don't have the same impact. The procedure involves restricting part of the stomach with a silicon band, but doesn't change the absorption process.)

The issue is a sensitive one for the bariatric-surgery community following a series of major studies raising questions about the long-term health benefits of the procedure. A large study of 60,000 gastric-bypass patients published in the Journal of the American Medical Association last October, found that 40.4 percent of patients who had the surgery were readmitted to a hospital at least once during the three years after surgery, double the 20.2 percent rate of hospitalizations in the three years prior to surgery. Some in the field hope the concerns about substance abuse will add to the growing interest in psychological counseling of patients.

Some research suggests that obesity might offer some protection against other types of addictions, including alcohol. A study of 9,125 adults published earlier this month in the Archives of General Psychiatry found that obese people had a 25 percent decrease in likeliness for substance abuse. And in 2004, researchers at the University of Florida, Gainesville, published an study of 298 women showing that obese women have lower rates of alcohol use than the general population. The researchers theorize that food and alcohol trigger the same reward sites in the brain. Some people may feed their addictive cravings with food; others with alcohol.

Neuroimaging studies suggest that obese people and substance abusers have abnormal levels of dopamine in the brain, contributing to cravings. "They always feel something is lacking, and in order for them to feel OK, they need to use something that boosts the dopamine in brain," says Gene-Jack Wang, chairman of the Medical Department Brookhaven National Laboratory.

Bankole Johnson, chairman of the department of psychiatric medicine at the University of Virginia, says gastric-bypass surgery provides a mechanical solution that leaves the underlying neurobiological problem untreated. "It's like a thirst," says Dr. Johnson. If you're thirsty -- and there's no water -- you'll drink lemonade."