Bariatric, or weight loss, surgery is the most effective treatment for severe obesity, but it's not magic. Maintaining post-op weight loss is challenging for most patients. A new study looked at what sorts of behaviors affect patients' successful and unsuccessful outcomes following their procedure. It found post-surgery behaviors thought to predict overall, long-term success actually did not predict patients’ ability to lose weight and keep it off.

The researchers followed about 1300 people enrolled in the Longitudinal Assessment of Bariatric Surgery (LABS-2) study of patients undergoing weight loss surgery at one of 10 hospitals across the United States. All had undergone gastric bypass surgery.

Pre-surgery eating patterns did not predict the likelihood of postsurgery weight regain.

The surgery creates a small pouch at the top of the stomach. This pouch is the only part of the stomach that receives food which greatly limits the amount a person can comfortably eat and drink at one time. It also means that fewer nutrients and calories are absorbed since food now bypasses a portion of the small intestine.

The average age of the participants was 46, and 80 percent were women. People in the study were weighed an average of eight times over a period of more than six years. The researchers wanted to see what kinds of behaviors were associated with successful and lasting weight loss post-surgery, and what tended to make people regain weight.

Unsurprisingly, becoming more physically active, avoiding fast food, and reducing behaviors such as binge eating, eating when full and eating continuously all helped people in the study lose weight and keep it off following gastric bypass surgery. Weighing themselves at least once per week also helped them lose weight and maintain weight loss, the University of Pittsburgh team found.

Younger people, and those with venous edema (swelling) ulcerations (sores), difficulties with activities such as bathing and dressing, as well as depression following surgery, were the most likely to regain weight.

Much of this is common sense, but there were some surprises, too. “Several behaviors doctors associated with weight regain were found to be unrelated,” Wendy King, lead author of the study and an Associate Professor in Epidemiology, said in a statement. For example, although how frequently a person ate fast food was associated with weight gain, the frequency of meals and eating out were not.

The study showed that it is difficult to predict the outcome of bariatric surgery based on patients’ pre-surgery status. While symptoms of depression after surgery were related to weight regain, depressive symptoms before surgery were not. And pre-surgery eating patterns did not predict the likelihood of postsurgery weight regain.

Finally, a close, long-term follow-up of patients helps them achieve the best weight loss results and health benefits following weight-loss surgery, the findings showed. As researcher Anita Courcoulas, a professor of surgery at the University of Pittsburgh Medical Center, points out, “It is important for clinicians and programs to talk to patients frequently starting soon after surgery about behaviors that can help them limit weight regain.”

The study was published in the Annals of Surgery.