How Fat Affects Rheumatoid Arthritis 

The fat in your body doesn’t just take up space. It’s an active organ that releases hormones called adipokines into your body. 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.

People who are obese have more pain and disability and faster disease progression than their thinner counterparts. In 2018, researchers at the University of Pennsylvania analyzed data from more than 23,000 patients with RA. Those who were obese (defined as having a body mass index of 30) became disabled much sooner than other patients – even those considered overweight (BMI of 25–29). 

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 and blocks blood flow and is the main cause of heart attack and stroke. People with RA already have a 50 percent higher cardiovascular mortality risk than the general population, says Jon Giles, MD, a rheumatologist and researcher at Columbia University Vagelos College of Physicians and Surgeons in New York City. “You don’t want to have fat that increases your risk of heart disease,” he says.

Biologics and certain conventional disease-modifying antirheumatic drugs may work less well in people with RA who are obese. Some researchers think these patients simply need higher doses to account for their excess weight. Another possibility is that fat cells can produce enough cytokines to sustain the inflammatory process despite medications. Eric Toussirot, MD, a professor of rheumatology in the Clinical Investigation Center for Biotherapy at the University Hospital of Besancon, in France, says there’s still another explanation. “The fat cells may attach to monoclonal antibodies like infliximab (Remicade) and render them nonfunctional,” he says. This supports the findings of a 2011 Dutch study showing that obese RA patients did less well on infliximab than other arthritis drugs. But it shoots down the notion that people who are obese need higher doses, since infliximab is given based on weight. 

One thing is clear: Obese RA patients have worse outcomes and a poorer quality of life than slender ones.