It’s not always easy to find the motivation to eat a balanced diet and be physically active when you’re dealing with a psoriatic arthritis (PsA) flare-up. Joint pain can make it hard to exercise. Fatigue can zap your energy for cooking and working out, and if you’re having skin lesions, you may not feel like getting sweaty or moving around outdoors.

However, research indicates several reasons why people with PsA may benefit from being mindful about healthy habits and a balanced weight. Higher body weight can put more pressure on the joints. A body mass index (BMI) score in the obese range is also associated with chronic inflammation and an increased risk for certain PsA comorbidities. Having more body fat may also cause some arthritis medications not to work as well.

Members of MyPsorasisTeam have expressed challenges with their weight, including one member who shared: “Because of the combination of PsA, direct joint changes, and all the secondary effects from steroids, I really struggle with weight issues.”

Another member echoed the importance of weight management: “I have had PsA for more than 50 years, and it gets worse over time. Plus, my extra weight doesn’t help. I would say to anyone with PsA, try to keep your weight down.”

Read on to find out what research has to say about the connection between BMI and inflammatory joint disease.

Does Weight Gain Cause Psoriatic Arthritis?

The exact cause of psoriatic arthritis remains unclear. Still, one study suggests that people with a BMI over 35 are nearly 2.7 times more likely to develop psoriasis than those with a lower BMI. Between 20 percent and 30 percent of people with psoriasis experience joint issues.

High inflammation levels are a characteristic sign of all autoimmune diseases. Carrying more fat (referred to as adipose tissue) on the body can contribute to low-grade inflammation. For example, people with obesity and PsA have been found to have higher levels of C-reactive protein, one of the several inflammatory biomarkers.

The link between PsA and weight has started to become apparent based on the results of multiple studies. For example, one study’s data suggested that individuals in the overweight category were almost two times more likely to develop PsA than those in the normal weight category. The risk increased along with weight, rising to three times higher for those with a BMI between 30 to 35 and six times higher for those with a BMI over 35.

Another similar study in the United Kingdom looked at PsA incidence in 75,000 participants with psoriasis. Here, the likelihood of developing PsA also increased incrementally for those with higher BMIs. Obesity is considered a risk factor for PsA, and it can also affect other common comorbidities of PsA, like cardiovascular disease.

Understanding BMI

BMI is calculated by dividing body weight in kilograms by height in meters squared.

The different BMI categories are as follows:

• BMI under 18.5 — Underweight
• BMI between 18.5 and 24.9 — Normal weight
• BMI between 25 to 29.9 — Overweight
• BMI of 30 or greater — Obesity

It’s important to note that a BMI score does not always equate with health. The American Medical Association considers BMI to be “an imperfect way to measure body fat in multiple groups given that it does not account for differences across race/ethnic groups, sexes, genders, and age-span.” Other factors, like waist circumference and your eating and exercise habits, can also help your rheumatology team identify whether you may benefit from weight loss.

How BMI Affects PsA Severity and Treatment

People with more body fat might have a weaker response to some PsA treatment options, like anti-tumor necrosis factor (TNF) biologics and some disease-modifying antirheumatic drugs (DMARDs). The dosages of drugs like intravenous ustekinumab (Stelara), infliximab (Remicade), and golimumab (Simponi) are currently adjusted based on body weight. However, higher doses of PsA therapies don’t always resolve efficacy issues for people with higher body weights.

Early findings suggest that DMARDs, including abatacept (Orencia), tocilizumab, or rituximab, may be preferable to anti-TNF agents for people with obesity. But more research is needed before specific recommendations can be made.

Having a higher BMI and PsA can also pose an increased risk of metabolic syndrome and comorbidities like type 2 diabetes, cardiovascular disease, and gout.

Can Weight Loss Help Psoriatic Arthritis?

People with any form of inflammatory arthritis (including rheumatoid arthritis and PsA) may find that losing some weight can be helpful for joint pain. Research shows that every pound of body weight puts 4 pounds of pressure on the knees. That means bringing your weight down by 10 pounds can feel like 40 pounds have been lifted from your joints. Not only will you likely be able to move more freely, but you may prevent some of the permanent cartilage damage that progresses more quickly when carrying extra weight.

Weight loss is not a cure for psoriatic arthritis. However, having a body weight in the normal BMI range has been shown to increase the effectiveness of many prescription PsA therapies, which may help improve PsA symptoms and lead to minimal disease activity. When your joints are less stiff and painful, you may find physical activity more enjoyable, making it easier to maintain healthy habits and a balanced weight.

Some members of MyPsoriasisTeam have found that weight loss helped. “What a difference the weight loss has made on my joint pain and even my skin,” one shared. Another said, “I’ve lost 38 kilograms and for some reason my psoriasis has disappeared.”

Does Joint Inflammation Cause Weight Gain?

Joint inflammation does not directly cause weight gain, but it may do so indirectly.

First of all, joint pain can be an indication that you're dealing with chronic inflammation. PsA is considered a chronic inflammatory disease and could mean your body is always inflamed at some level. This kind of inflammation is associated with excess body fat, which is often tied to weight gain.

Secondly, inflamed joints can cause pain and stiffness that make it harder to exercise. If your symptoms are preventing you from exercising regularly, you might gain weight.

A member of MyPsoriasisTeam said, “Losing your mobility sucks! It's depressing! Debilitating, frustrating, sad. Not good for weight loss!”

Does Psoriatic Arthritis Make You Gain Weight?

As noted above, certain aspects of PsA could be associated with weight gain. Chronic inflammation and a lack of exercise could both contribute to weight changes. However, there is nothing absolute about that. While you might be more likely to gain weight with psoriatic arthritis, it’s also possible to lose weight or stay the same.

Weight Loss When You Have Psoriatic Arthritis

A combination of exercise and healthy eating are essential for feeling your best, especially for people with PsA. But that doesn’t mean you need to overdo it. For example, one member of MyPsoriasisTeam who started exercising said: “I had to start really slow and work up, little by little. The more I did, the better I got. … Doing something is far better than nothing. You don’t have to kill yourself to see results.”

It can be especially difficult to be physically active when you’re experiencing joint stiffness and pain. You can talk to your doctor about exercises that won’t put too much strain on your joints. Activities like gardening, dancing, swimming or other water exercises, walking, and tai chi tend to put less stress on your joints.

The Centers for Disease Control and Prevention (CDC) recommends simple tips for getting started with weight loss. These include:

• Write down your motivation for weight loss — If your goal is to lose weight to reduce symptoms of psoriatic arthritis, write it down and put it somewhere where you can be reminded of it daily.
• Keep a journal — Keep track of what you eat and drink and how it makes you feel, your sleeping and eating habits, stressors, and physical activity. This can help you understand what helps you feel healthiest.
• Set goals that are specific and realistic — For example, “I want to walk for 15 minutes twice this week” is more specific than “I want to exercise more.”
• Look for support — You may consider joining an exercise class or sharing healthy recipes with loved ones. Either way, it’s important to surround yourself with people who will support your new healthy habits.
• Keep track of your progress — Continue to check in on your goals and evaluate your current plan. You may need to adjust your weight loss plan or figure out where you need more support.

Talk to your rheumatologist about meeting with a physical therapist or registered dietitian for more support with exercise and nutrition. Even if you’re unable to reach an “ideal” BMI or your weight doesn’t change much, your quality of life with PsA may still improve from choosing new healthy behaviors. Finding some relief from swollen joints and other PsA symptoms can serve as a motivator to take better care of your overall health.

Talk With Others Who Understand

MyPsoriasisTeam is the social network for people with psoriatic disease. Here, more than 132,000 members from around the world come together to ask questions, offer support and advice, and meet others who understand life with psoriatic arthritis and psoriasis.

Have you noticed a connection between weight changes and how your joints feel? Do you have any tips for others about exercising or eating well as part of your psoriatic arthritis care? Share your insight in the comments below, or start a conversation by posting on MyPsoriasisTeam.