Doctors treating overweight or obese patients often prescribe exercise as part of a regime to take off pounds. However, a new study indicates that some people’s ability to exercise may be hampered by a variety of gastrointestinal problems that frequently affect individuals who are overweight.

A team of researchers studying nearly 1,000 men and women participating in a randomized trial evaluating three weight-loss programs in Minnesota found that associations between gastrointestinal symptoms, diet and exercise may have implications for the treatment of both obesity and gastrointestinal problems. The physiological mechanisms linking gastrointestinal symptoms, obesity and exercise still need to be determined, said psychologist Rona Levy, lead author of the study and a University of Washington professor of social work whose research focuses on common gastrointestinal disorders such as irritable bowel syndrome in adults.

“Our main finding is that the amount of exercise people in a weight loss program do is related to gastrointestinal symptoms.

In statistical terms, this means exercise is protective against gastrointestinal symptoms. This isn’t surprising, but it has not been demonstrated before with this population. Science has now validated what people have been guessing,” she said.

“But we don’t know if this is a ‘did the chicken or the egg come first’ kind of a thing. We are not sure which is the key, exercise or gastrointestinal symptoms. It is plausible that if a physician put a patient on an exercise program to lose weight the GI problems experienced might hamper the patient’s ability to exercise.”

People in the study reported experiencing a variety of problems: 19 percent said they had abdominal pain, 13 percent had irritable bowel syndrome, 25 percent had diarrhea and 20 percent had bloating.

Data were collected from a larger two-year study evaluating telephone- and mail-based interventions for weight loss. Seventy percent of the 983 participants were women and all were classified as obese or overweight. Participants ranged in age from 20 to 89.

Levy said the more people weighed the more gastrointestinal symptoms they tended to report. People who began limiting their dietary intake of fat and increased their amount of fiber by eating more vegetables and fruit reported lower levels of GI symptoms. However, when the researchers looked at all the factors together, rather than comparing two of them, these relationships did not come out as the most significant ones.

“This study is another argument for exercise. Even though anyone engaging in a weight-loss program should know that gastrointestinal symptoms may impede their ability to exercise, those symptoms may also be alleviated by exercise,” said Levy.

Co-authors of the study are Jennifer Linde and Robert Jeffery, epidemiologists at the University of Minnesota School of Public Health, Michael Crowell, a psychologist at the Mayo Clinic and. Kayla Feld of a Harvard University student.

The National Institutes of Health funded the research and the study was published in the current issue of journal Clinical Gastroenterology and Hepatology.