A 2001 study "The psychology of gastric bypass surgery" (Glinski J, Wetzler S, Goodman E. Obes Surg.2001 Oct;11(5):581-8.) stressed the importance of psychological evaluation of GBP candidates and post-surgical psychological support services. The study looked at 115 GBP surgery candidates who completed a clinical interview and a self-report measure, the MMPI-2. Researchers concluded that there was a high prevalence of psychopathology and personality disturbance that can have may have a negative effect on post-operative outcome.

After having gastric bypass surgery, people are forced to eat small portions of food. After giving up overeating, many adopt a new compulsion. This is known as addiction transfer or transferring addictions. Addiction transfer occurs when someone is unable or unwilling to rely on a specific compulsion, so he or she switches to a new compulsion. Addiction transfer tends to occur when the person has not dealt with the underlying issues behind the compulsion. For example, someone may think she's depressed because she's overweight. After GBP, the depression continues because the real cause of the depression was more than just being overweight. By some estimates, there are millions of people who have undergone gastric bypass who are now dealing with issues of addiction transfer.

One such example is Carnie Wilson, one of the best-known gastric bypass cases, who became an alcoholic after the size of her post-surgery stomach made it impossible to rely on overeating as a coping mechanism.

The April 2007 issue of Bariatric Times featured article discussing addiction transfer (Transfer of Addiction and Considerations for Preventive Measures in Bariatric Surgery: Part II). The author, Dr. Melodie K. Moorehead, has specialized in bariatric surgery psychology for more than two decades. According to Moorehead, when someone with a gastric bypass transfers addiction, it can be to almost any behavior. "The addiction factor is by no means limited to excessive food or alcohol consumption," says Moorehead. "It can show up as uncontrolled spending, drug-related difficulties, smoking, sexual promiscuity, or compulsive gambling. In fact, virtually any behavior exhibited in excess can interfere with the goals of a comprehensive bariatric surgery program."

Moorehead stresses that those with a gastric bypass are facing a life-long recovery. She states, "We could learn from the worldwide fellowship of Alcoholics Anonymous, and their lifelong program strategy, by ensuring the provision of lifetime recovery support for bariatric surgery patients."