Women who are overweight or obese appear to have an increased risk of developing the chronic pain syndrome known as fibromyalgia, a new study suggests.
If they are also sedentary, the risk is even greater, said lead researcher Paul Mork, of Norwegian University of Science and Technology in Trondheim, Norway.
The study is published in the May issue of Arthritis Care & Research.
Fibromyalgia is marked by widespread pain lasting more than three months. The pain strikes so-called "tender points" in the neck, shoulders, back, hips, arms and legs.
The condition is also marked by fatigue without apparent cause, mood disturbances, sleep problems and headaches. More women than men have it, and experts don't thoroughly understand its cause.
The condition may be due to dysfunction in the nervous system and other problems, and it is thought to be affected by genetic susceptibility.
In the new study, Mork and his colleagues turned to a data base of nearly 16,000 women in Norway who had responded to health surveys. Among the participants were 380 who developed fibromyalgia during the 11-year follow-up.
Mork's team compared the data from patients with the healthy respondents, including body-mass index (BMI) and exercise habits.
Exercise and a healthy body weight were found to be protective.
"According to previous findings reported in the literature, we expected that regular leisure-time physical exercise would have a protective effect on future development of fibromyalgia [FM]," Mork said. "However, we only found a weak association between development of FM and exercise. However, it should be noted that we were not able to differ between different types of exercise, and it might be possible that some exercise types are more beneficial than others in protecting against future development of FM," he added.
"Women who reported exercising four times per week [or more] had a 29 percent lower risk of fibromyalgia compared with inactive women," Mork said in a news release about the study.
Those who exercised two to three times a week were about 11 percent less likely to get fibromyalgia.
Being overweight -- with a BMI of 25 or higher -- was a strong independent risk factor, with the heavier women having a 60 percent to 70 percent higher risk of developing the condition compared to the healthy weight women.
The overweight women who exercised an hour or more a week, however, were less likely to get the condition than were overweight women who were inactive.
Mork's advice: Regular exercise, which can help maintain weight, may serve as a "buffer" against the symptoms that eventually lead to fibromyalgia.
The results are entirely plausible, said Dr. Patrick Wood, senior medical adviser for the National Fibromyalgia Association, who cares for many fibromyalgia patients.
But with the condition, there are often the chicken-egg questions, he added, such as whether the pain leads to the inactivity or weight gain or vice versa. "It's difficult with any level of assurance to know what's driving what," Wood said. There could be underlying factors driving both excess weight and pain sensitivity, he noted.
The inflammation that is associated with obesity may heighten pain sensitivity, Wood added.
More study is needed, Wood said. Until more is known, however, he would advise people who want to avoid the condition to maintain a healthy weight and exercise regularly. That's especially wise for those with a family history of fibromyalgia, he stressed, because he has found that it does tend to run in families.
For those already diagnosed with the condition, Wood said, "some data show if you exercise and keep your weight down you may have less pain."