Trends showed most symptoms worsened with higher BMI category, but for the most part, the difference in the severity of symptoms was statistically significant for the highest BMI group compared with the other groups. “The group comparison showed the difference was primarily seen between the severely obese and the other groups,” Dr. Oh says. “Symptom severity is very pronounced when obesity is more severe.”

Why is there a relationship between BMI and the severity of fibromyalgia symptoms? Dr. Oh and her team write that multiple factors may be at work, including a higher level of pain receptors in fat tissue, elevated levels of pro-inflammatory cytokines, loss of physical fitness and an increase in mechanical loads on the body. And the higher rate of obesity in fibromyalgia patients “may be caused by a vicious circle of pain and physical inactivity.”

Dr. Oh urges people with fibromyalgia to find a way to stay active despite the chronic pain and fatigue that come with it, and believes doctors should discuss weight-loss strategies with their fibromyalgia patients.

“Those who are severely obese may need more help for weight-loss management,” she says. “The basic message is that they have to stay active and exercise by starting slowly and gradually in terms of duration, intensity and frequency. It’s more than saying ‘lose weight.’ They need specific recommendations or to see a dietitian or endocrinologist or get other treatment options.”

Akiko Okifuji, PhD, a psychologist at the Pain Research and Management Center and professor at the University of Utah, in Salt Lake City, says it makes sense that those carrying around extra weight would experience more symptoms. Okifuji, who was not involved in Dr. Oh’s study, conducted earlier research on fibromyalgia and obesity, which found that obese fibromyalgia patients had more pain, less physical strength and more sleep problems.

“Both obesity and fibromyalgia are very different persistent conditions that impact overall health, physical well-being as well as quality of life,” Okifuji says.

She believes people intuitively know what Dr. Oh’s study showed – that severe obesity is bad for fibromyalgia patients. “But it’s good to show it scientifically,” Okifuji says. “Patients need proper nutritional education. It is difficult when you don’t move much. Sometimes food becomes a comfort. They need education on how to deal with that and how to maximize calorie burning while minimizing intake. When dealing with chronic fatigue and chronic pain, it is very difficult to do weight management. The key issue for the scientific and clinical community is to come up with an effective [weight management plan] for people who can’t move that much. It’s a tricky thing.”