In one of her numerous lupus studies, obese lupus patients performed significantly worse than those who were not obese in three areas of functioning: work, basic physical functions (such as climbing stairs or bending over) and daily activities (including self care and social activities).

“Not only did obese women do worse at first look, but they had greater decline in functioning,” says Katz.

In another study, obese and/or inactive women with lupus had a higher rate of cognitive impairment – although it didn’t show that one condition caused the other.

As in OA and RA, the cytokines that fat releases create inflammation in different parts of the body. “Fat tissue is not inert,” Katz says, echoing other researchers.

But it’s hard to know if obesity is a cause or an effect of health risks associated with lupus, she says. For example, people with lupus have a higher risk of heart disease. “If you are fat, maybe you release more inflammatory cytokines, which affects cardiovascular risk.”

In addition, even though obesity is categorized as a BMI of 30 or more, Katz’s studies have found that patients with lupus who have a BMI of 27 have the same cardiovascular risk factors and disability as heavier lupus patients. “Really, if you want to set a criterion for obesity in lupus using BMI, you need to move the number lower, to 26.8,” she explains.

And, as with other forms of arthritis, there’s the issue of body mechanics. “If you are obese, the loading on your joints will make the pain worse,” she says.

Fibromyalgia

What It Is

Fibromyalgia is a chronic pain disorder that affects 3 to 6 percent of Americans, mostly women. Symptoms are widespread muscle pain and “tender points,” and can include fatigue, sleep problems, depression, bladder and bowel irritability and cognitive difficulties.

Why Obesity Matters

Eighty percent of people with fibromyalgia are overweight or obese, compared with 67 percent in the general population. Numerous studies have shown that heavier fibromyalgia patients have worse symptoms and a lower quality of life than those of normal weight. Additionally, being overweight, especially if you are inactive, puts you at greater risk of developing fibromyalgia, according to a large Norwegian study.

Both fibromyalgia and obesity are characterized by the malfunctioning of the HPA axis – a communication system between glands that helps regulate the immune system, digestion, mood, hormones and other functions. Understanding the HPA axis issue could lead to better treatments for both conditions, says Akiko Okifuji, PhD, a psychologist at the Pain Research and Management Center and professor at the University of Utah, in Salt Lake City.

Each condition poses “a potential barrier to treat the other,” says Okifuji. “In order to help people attain reduction in symptoms and weight, we have to target both.”