Carrying excess body weight increases pain levels and the extent of widespread pain in people with fibromyalgia; it also ratchets up the severity of other symptoms of chronic pain syndrome. Studies have shown that overweight and obese people with fibromyalgia aren’t as physically strong or flexible, have more sleep problems, experience greater levels of anxiety and depression, and endure a lower quality of life than healthy-weight people with fibromyalgia.
The link between obesity and pain is strong, says Akiko Okifjui, Ph.D., researcher in the Pain Management Center at the University of Utah in Salt Lake City. “Research shows obesity increases symptom severity and pain sensitivity in almost all chronic pain conditions, including fibromyalgia and osteoarthritis,” she says.
The more people weigh, the more pain they have, she says. A 2015 editorial on the pain-obesity link published in Pain Management, for example, reported that people who are overweight (body mass index [BMI] 25–25.9 kg/m2) have 20% more chronic pain than healthy-weight people, while those who are obese (BMI 30–34 kg/m2) or very obese (BMI 35–39 kg/m2) have 68% and 136% more pain, respectively.
Overloaded joints explain part of the pain–fibromyalgia connection, says Okifuji.
In a 2010 study published in the Journal of Pain, Okifuji and her colleagues evaluated pain and other fibromyalgia symptoms in 215 people with the syndrome, finding that obese people had heightened sensitivity to pain compared with those of lower weights and that this sensitivity was higher in lower body areas. They observed similar, smaller effects in overweight people.
“This additional sensitivity in the lower extremity also points to mechanical load as a cause of pain in fibromyalgia,” she says.
“Researchers are starting to equate obesity with a generalized state of constant low-grade inflammation,” she says. “While fibromyalgia isn’t an inflammatory disease like rheumatoid arthritis, increased overall inflammation probably plays a role in increasing pain levels and sensitivity.”
One factor may be a growth hormone, insulin-like growth factor-1 (IGF-1), that drops as BMI rises. IGF-1 appears to reduce fibromyalgia-related fatigue, which patients often rank as the second-most bothersome symptom – after pain – of the syndrome, says Jan Bjersing, Ph.D., a researcher in the Department of Rheumatology and Inflammation Research at the University of Gothenburg in Sweden.
In a 2013 Arthritis Research & Therapy study, Bjersing and colleagues tested blood levels of IGF-1 and other measures in 48 people with fibromyalgia taking part in a supervised exercise program. They found that 15 weeks of twice-weekly 45-minute walking sessions significantly raised IGF-1 levels and decreased fatigue in normal-weight, overweight and obese participants – though the effects occurred faster in lighter-weight people.
“How exercise decreases fatigue is not known, but our data indicate that IGF-1 activity is involved,” Bjersing said. “The effect of exercise in our recent study was strongest in lean participants, but after six months there was benefit also in overweight and obese participants.”
Weight loss also improves fibromyalgia symptoms. A 2012 trial published in Clinical Rheumatology compared individuals with fibromyalgia who lowered their BMIs about three points, enough to move most from an obese to overweight classification, with their counterparts whose weight remained the same. Weight losers significantly improved in measures of inflammatory proteins and almost all fibromyalgia symptoms, including pain, depression, and sleep.
Okifuji other researchers have found that obesity in fibromyalgia reduces sleep quality compared with healthy-weight people with the syndrome. “This poorer sleep may also be contributing to pain,” she says.
The physiologic pathway connecting pain and poor sleep in fibromyalgia appear to run both ways. A 2014 study published in The Clinical Journal of Sleep Medicine found that, among 55 women with fibromyalgia, pain significantly reduced sleep quality, and poor sleep quality significantly increased pain.
“Poor sleep also reduces people’s ability to cope with pain, making it harder for them to focus on other things, and to take part in physical activity,” says Okifuji. “It’s encouraging that both exercise and weight loss can lead to a reduction in symptom severity.”
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