Weight-loss surgery was supposed to be Chevese Turner's salvation -- a last resort in her battle against obesity and binge eating. Instead, her 2007 lap band procedure catapulted her into full-blown bulimia.

"I had always struggled with binge eating, and my relationships with food didn't change just because of the lap band. Even though binging is really painful when your stomach is restricted like that, I would still binge knowing that I would throw it up. I felt like finally I could be bulimic, like this was what I wanted all along," says Turner, 43, of Soverna Park, Md.

Turner knew she had a binge eating disorder going into surgery, but after experiencing cardiac complications attributed to a lifetime of yo-yo dieting, she was desperate to lose weight. Instead of solving her overeating problem, however, the surgery only changed its form: for 18 months following the surgery Turner regularly binged and purged.

Only after going into intensive therapy to cope with the binging behavior she had experienced since age 5 did Turner, who now runs the Binge Eating Disorder Association, build a healthy relationship with food and her body.

When multiple traditional diet methods fail, weight-loss procedures such as the band are seen as a last hope for getting obese patients to eat more healthfully and lose weight. For an underrecognized minority of patients, however, the surgery only triggers a different kind of disordered eating. For Turner, it was bulimia, for others, it's anorexia. For one fellow patient in Turner's community, the anorexia was so severe that it ultimately took his life.

Sixty percent of individuals seeking treatment for obesity have some kind of eating disorder, usually binge eating, according to a 2007 Harvard study. It is these individuals, who already have an unhealthy relationship with food and their bodies, who are at most risk of developing further eating disorders post-surgery, says Lisa Lilenfeld, a psychologist and president of the Eating Disorders Coalition at Argosy University in Washington, D.C.

Lap band or gastric bypass surgery is not likely to create an eating disorder where there wasn't one, she explains, but "the most likely thing is that people had untreated or unsuccessfully treated binge eating disorders before surgery will continue to have problems after surgery. The problem is, it becomes physically challenging and potentially dangerous to binge like this because of the structural changes in the stomach," she says.

On the other end of the spectrum, patients who used to overeat now overshoot with their weight loss, severely limiting their caloric intake to the point of malnutrition and anorexia.

"I've had a number of patients go from very obese to very underweight, so much so that they need to be rehabilitated with intravenous nutrition," says Dr. Donald Kirby, a gastroenterologist at the Cleveland Clinic who treats patients undergoing bariatric weight-loss surgery.

Because there are so no statistics on how many of these patients experience eating disorders post-op, it's difficult to gauge the scope of this issue and there is much debate over its prevalence between the surgeons who perform the procedures and the therapists who treat eating disorders down the line. Dr. Mitch Roslin, a bariatric surgeon at Lenox Hill Hospital in New York, has performed thousands of bariatric surgeries and he says he only sees one or two cases a year of eating disorders, but psychologist Lilenfeld believes it's much more common than that.

Binge Eating: Hiding an Eating Disorder

Technically, those with diagnosable eating disorders are not advised to undergo weight-loss procedures, but because each hospital and insurance company has different psychological screening requirements, many patients with mental health problems slip through the cracks.

In some cases, psychological screenings consist of asking only a couple of basic questions that don't even address eating disorders or mental health concerns, says Dr. Leslie Seppinni, a therapist who specializes in treating obesity. "Then after the surgery, most doctors fail their patients in terms of follow-up. There are some group sessions with other patients, but that's about it."

In Turner's case, however, her health insurance had relatively rigorous requirements for surgery approval, including an eating disorder screening and a letter from her therapist. But for those who are desperate to get the surgery at all costs, she says it's relatively easy to get around these requirements by answering the questions "right," as she did.

Because of insufficient screening or deception, Lilenfeld says about a third of all patients who undergo weight-loss procedures are believed to have "severe binge eating disorder" going into surgery, though not all of these patients will go on to develop other eating disorders post-op.

Anorexia/Bulimia After Surgery: Medical or Emotional?

One of the reasons that true anorexia and bulimia may not be recognized after bariatric surgery is that the symptoms of these eating disorders can mimic some of the expected adverse affects of the surgery.

In the months following surgery, the stomach has to heal and slowly expand, which makes eating difficult and sometimes painful. Patients who eat too much will sometimes throw up because it's the only way to relieve the pain in their stomach, not because they are compulsively trying to get rid of calories. Similarly, the indigestion, diarrhea and acid reflux that can occur post-op leads some patients to avoid eating altogether just because eating becomes an unpleasant experience. These patients will become malnourished and resemble anorexics, but the psychological aspect of the disorder is not there.

It is important to distinguish between these medical reasons for anorexic/bulimic behavior and true, psychological cases of eating disorders, says Seppinni, who has traveled the country interviewing people about their experience with obesity, weight loss and bariatric surgery. In true cases of eating disorders, it's about the addiction to overeating getting transmuted into another addiction. For some, they become compulsive exercisers, for others, alcoholics, for still others, anorexics. "You take away the coping strategy they've been using all their lives, and the addiction has to go somewhere else," she says.

The "loss" of binging as a coping strategy was palpable for Turner following her surgery. "I lay in bed and cried for a week because I couldn't eat. Eating was the way I soothed myself my whole life. As soon as I could binge again, even though it was extremely painful, I did," she says.