How Fat Affects Rheumatoid Arthritis 

Fat doesn't just add pressure to joints, it cranks up inflammation and may affect arthritis drugs.

By Linda Rath | Updated April 28, 2022

Being overweight can worsen rheumatoid arthritis (RA) symptoms, set you up for other health problems and may make certain arthritis medications less effective. About two-thirds of people with RA are overweight or obese — the same proportion as in the general population. But when you have RA, extra body fat can create extra problems.

Why Obesity Matters

The fat in your body doesn’t just take up space. It’s an active organ that releases hormones called adipokines. Some affect glucose metabolism; others play a role in your immune system and regulate your appetite. If you are of healthy weight, your fat cells mainly produce beneficial adipokines. But excess fat tissue releases high levels of cytokines — proteins that can cause inflammation throughout your body. These are the same proteins produced by joint tissue in RA. In addition to causing other health problems, cytokines make existing joint inflammation worse.

Disease Progression

People who are obese have more pain and disability than their thinner counterparts. Yet they also have less inflammation and slower disease progression as seen on imaging tests. Part of the problem may be a disconnect between findings on physical exam — such as swollen joint counts — and what shows up on ultrasound or MRI. A physical exam may not be a particularly reliable way of determining disease activity and progression in people who carry extra weight.

Other Health Problems

Obesity doesn’t just make arthritis worse; it also causes other health problems. The same fat-related cytokines that attack your joints significantly increase your chances of developing type 2 diabetes and heart disease. Inflammatory cytokines make it harder for insulin to get into cells. This causes glucose to build up in your blood and eventually leads to diabetes.

Inflammation also causes plaque to form faster in the arteries of people who have RA. This slowly narrows blood vessels, blocks blood flow and is the main cause of heart attack and stroke. People with RA already have a 50% higher cardiovascular mortality risk than the general population, says Jon Giles, MD, an associate professor of medicine, researcher and rheumatologist with Columbia University Medical Center. “You don’t want to have fat that increases your risk of heart disease,” he says.

Response to Treatment

Some research suggests that certain arthritis drugs, especially tumor necrosis factor (TNF) blockers like infliximab (Remicade) and adalimumab (Humira) drugs don’t work as well when people with RA are obese. Other studies haven’t had found any difference in medication effectiveness based on weight. And one large study, using a decade’s worth of data from more than 23,000 veterans with RA, reported that methotrexate and TNF blockers were less effective in low- and normal-weight people than in those who were overweight. Since there haven’t been direct comparisons of different medications in RA patients who are obese, there’s no way to account for these varied results. Still, some doctors may increase the dose of a drug like infliximab in obese patients. According to French researcher Eric Toussirot, MD, fat cells may attach to drugs like infliximab, making them nonfunctional.

Nevertheless, obese RA patients have worse outcomes, a greater risk of other chronic conditions and a poorer quality of life than normal-weight patients do.

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