How Fat Can Worsen Arthritis
Excess fat increases not only pressure on joints but also inflammation.
By Andrea Kane
If you were to ask people to name a health problem related to obesity, odds are good they’d say “heart disease” or “diabetes.” And they’d be right; those two chronic diseases have a very strong relationship to excess weight.
What’s not as commonly known is that obesity can raise the risk of developing certain types of arthritis; in all cases, obesity makes arthritis worse — and in ways that might surprise you. More than 1 in 5 Americans has been diagnosed with arthritis, but according to the Centers for Disease Control and Prevention (CDC), that number jumps to more than 1 in 3 among obese people — and more than 42% of Americans are obese.
Here’s a look at what fat does to arthritis, as well as some tips to put you on the road to losing weight.
Osteoarthritis (OA) is the most common type of arthritis, affecting more than 32.5 million Americans. It is characterized by the breakdown of cartilage — the flexible but tough connective tissue that covers the ends of bones at joints. Age, injury, heredity and lifestyle factors all affect the risk of OA.
Why Obesity Matters
OA has a logical link to obesity: The more weight that’s on a joint, the more stressed the joint becomes and the more likely it will wear down and be damaged.
“Weight plays an important role in joint stress, so when people are very overweight, it puts stress on their joints, especially their weight-bearing joints like the knees and the hips,” says Eric Matteson, MD, emeritus chair of the rheumatology division at the Mayo Clinic in Rochester, Minnesota.
That’s why people who are overweight are at greater risk of developing arthritis in the first place. And once a person has arthritis, “the additional weight causes even more problems on already damaged joints,” says Dr. Matteson.
In addition, fat itself is active tissue that creates and releases chemicals, many of which promote inflammation.
“These chemicals can influence the development of OA,” explains Jeffrey N. Katz, MD, a professor of medicine and orthopedic surgery at Harvard Medical School and Brigham and Women’s Hospital in Boston.
Learn more about the link between fat and osteoarthritis.
Rheumatoid arthritis (RA), affecting up to 1.5 million Americans, is an autoimmune disease in which the body’s immune system attacks its own joint tissue. This creates inflammation throughout the body and can lead to joint erosion and pain.
Why Obesity Matters
The inflammatory chemicals from fat are culprits in RA. Some of these chemicals, called cytokines, can impact different body systems, including musculoskeletal and cardiovascular systems. Many types of cytokines are released by fat tissue, and researchers are working to identify them and understand the specific effects of each kind.
One important group is called adipokines, and most types of adipokines promote inflammation — “not a good thing in RA,” says Jon Giles, MD, an associate professor of medicine in the division of rheumatology at Columbia University Vagelos College of Physicians and Surgeons in New York City.
Other cytokines released by fat include tumor necrosis factor-alpha (TNF-alpha) and interleukin-1 (IL-1). Both are overactive in RA and cause inflammation.
And people with RA — including those who have a body mass index (BMI) in the normal range — have yet another reason to watch their diet and exercise. “The disease process changes body composition in an unfavorable way; it favors having more fat and less muscle,” says Dr. Giles, who has conducted many studies on the effects of body composition and inflammatory arthritis.
In addition, researchers have found the excess fat is often located around the abdomen (known as visceral fat), which is a risk factor for insulin resistance (diabetes) and cardiovascular problems — and RA patients are already at higher risk of heart attack, stroke and other cardiovascular events than the general population.
Read more about fat and RA.
FAT AND GOUT
Gout is a form of inflammatory arthritis that occurs when an excess of uric acid in the body leads to the formation of uric acid crystals in the joints, triggering painful attacks, most commonly in the big toe.
Why Obesity Matters
Obesity is closely linked to gout; as the country’s obesity rate has gone up, so has its rate of gout. According to studies, about 70% of people with gout are overweight and 14% are obese. Being obese puts a person at a higher risk of developing gout in the first place, and of getting gout years earlier than someone of normal weight.
“In the highest [weight] group versus the lowest group, it could be a tenfold or higher risk of developing gout,” says gout expert Hyon Choi, MD, a professor of medicine and director of clinical epidemiology in rheumatology at Massachusetts General Hospital in Boston. Dr. Choi has authored pivotal population-based studies examining the link between gout and obesity.
Studies have shown that losing even a small amount of weight can lower uric acid levels, and losing more weight has a bigger effect on reducing uric acid. “Losing weight drags down uric acid levels. If you get rid of the root cause, your risk will drop,” says Dr. Choi. Learn more about gout and its link to obesity.
FAT AND PSORIATIC ARTHRITIS
Psoriatic arthritis (PsA) is an inflammatory, autoimmune form of arthritis that affects up to 30% of people with psoriasis, an autoimmune condition that affects the skin. Psoriasis usually precedes psoriatic arthritis.
Why Obesity Matters
According to studies, obesity is a risk factor for psoriasis and is associated with more severe disease. People with psoriasis are more likely than people without it to have a higher BMI and higher levels of the obesity-related hormone leptin. One of the first studies to look at the link between psoriasis and the development of PsA found that psoriasis patients who are obese at age 18 had triple the risk of developing PsA than those with a normal BMI — and they developed PsA earlier in life.
“It is a double whammy; first they get psoriasis, then they get psoriatic arthritis,” says Dafna Gladman, MD, professor of medicine at the University of Toronto and co-author of many studies on psoriatic arthritis.
The exact mechanism, however, is unknown. “There are a lot of metabolic things going on [in obesity] — adiponectin, leptin, pro-inflammatory cytokines that are increased. We don’t know if it is just the fat, or if it is what the fat is associated with,” says Dr. Gladman.
What is certain is that being overweight or obese plays a role in PsA. “Because you carry around more weight, especially in the lower extremities and back, there are additional forces at play,” says Dr. Gladman. “Also, when you are overweight, it’s difficult to figure out the dose of medication you might need. [Dosing of infliximab] Remicade is weight-related, but other drugs don’t have that, so obese patients may be undertreated because we don’t know the precise dose we should be using.”
FAT AND LUPUS
Systemic lupus erythematosus is a chronic, inflammatory autoimmune disease that primarily affects women of color. The body’s immune system attacks its own tissues and organs, leading to numerous symptoms that are often mistaken for other diseases.
Why Obesity Matters
Several studies have found that the rates of obesity are higher in people with lupus than in the general population. Obesity in patients with lupus is associated with high levels of disability and possibly cognitive impairment.
“What we found is that there is a higher rate of obesity among women with lupus than there is in general population, and there is a big effect of obesity on functioning,” says Patricia Katz, PhD, professor of medicine and health policy at the University of California, San Francisco.
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.”
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.
Learn more about the association between lupus and fat.
FAT AND FIBROMYALGIA
Fibromyalgia is a chronic pain disorder with widespread muscle pain and “tender points.” Symptoms can include fatigue, sleep problems, depression, bladder and bowel irritability and cognitive difficulties. While studies show varying rates of prevalence, it is thought to affect up to 6% of Americans, mostly women.
Why Obesity Matters
In the U.S., about 43% of people with fibromyalgia have obesity, and 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 raises the risk of developing fibromyalgia, especially among those who are not active, according to a large Norwegian study.
Both fibromyalgia and obesity are characterized by the malfunctioning of the HPA axis — 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.”
Read more about how fat affects fibromyalgia.
Updated April 2021
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