Eating habits and physical activity have a greater impact on weight-loss surgery's long-term success than measures like counting calories, a new study finds.

Researchers also found that evaluation of patients' mental health and eating habits before weight-loss (bariatric) surgery did not help predict who would be successful in keeping weight off years afterwards.

"Bariatric surgery is the most effective treatment for severe obesity. It results in sustained weight reduction and remission of diabetes and other health problems in the majority of patients," said study author Wendy King. She's an associate professor of epidemiology at the University of Pittsburgh's School of Public Health.

"However, as with all types of weight-loss interventions, patients usually regain at least some of the weight they initially lose," she added in a university news release.

The study included nearly 1,300 adults who had a type of weight-loss surgery called Roux-en-Y gastric bypass. The patients were followed for an average of 6.6 years.

Limiting sedentary behaviors (such as watching TV), self-weighing at least once a week, avoiding fast food, and correcting "problematic" eating behaviors were all factors associated with a greater chance of limiting weight gain after weight-loss surgery. Problematic behaviors included eating continuously, eating when full, loss of control and binge eating.

Younger patients were likely to gain more weight than older ones. Other characteristics linked with higher weight regain included having venous edema with ulcerations -- a disease of the veins accompanied by sores on the skin; difficulty with daily physical tasks such as bathing, dressing and walking; and symptoms of depression after surgery.

"This may sound like common sense," King said. "But several behaviors and characteristics that clinicians hypothesized to matter were not related to weight regain. For example, while frequency of fast food consumption was associated with greater weight regain, frequency of meals and eating at restaurants were not," she explained.

According to study senior author Dr. Anita Courcoulas, "As clinicians, we know that weight maintenance is the most important, yet challenging, aspect of long-term post-bariatric surgery care." Courcoulas is chief of minimally invasive bariatric surgery at the University of Pittsburgh Medical Center.

"Because we found that most individual patient characteristics at the time of surgery do not clearly identify those most at risk for poor weight-loss maintenance after surgery, it is especially important that clinicians and programs engage with patients early and often after surgery about behaviors that can aid in limiting weight regain," Courcoulas said.

The study was published April 4 in the journal Annals of Surgery.