An extensive body of research supports an association between psoriasis and obesity. Psoriasis is a chronic skin condition that causes inflammation and the accelerated production of skin cells. According to research, obesity, defined as a body mass index (BMI) greater than 30, doubles a person’s risk of developing psoriasis. Obesity has also been found to lead to poorer long-term clinical outcomes for people with psoriasis.

What Is Psoriasis?

Psoriasis is a chronic inflammatory skin disease that affects between 2 percent and 3 percent of the general population. It is an autoimmune disease, meaning it occurs when the immune system mistakenly attacks the body’s own healthy tissues. In people with psoriasis, the skin builds up more quickly than it can shed, resulting in patches of thick, scaly skin that can itch, crack, and bleed. These patches, referred to as plaques, can be red with white or silvery scales or a purple or gray color.

Experts aren’t sure exactly why some people develop psoriasis. It is believed that several factors play a role in the disease, including genetics, immune dysfunction, and environmental factors. Psoriasis has also been associated with numerous comorbidities (co-existing health conditions), including psoriatic arthritis, cardiovascular disease, and obesity.

What Is Obesity?

Obesity is an increase in energy deposits stored in the form of body fat, resulting in excess weight. Obesity usually results from a combination of factors, including genetics, environment, and personal diet and exercise habits.

Obesity is diagnosed using a person’s BMI. BMI is determined by dividing a person’s weight in pounds by their height in inches squared. According to the World Health Organization, a BMI between 25 and 29.9 is overweight, and a BMI greater than 30 is classified as obesity. BMI is not a direct measure of body fat — some people, such as muscular athletes, may be classified as obese based on their BMI, despite having a normal amount of body fat. Still, BMI provides a reasonable estimate of body fat for many people.

Obesity leads to an increased risk of developing potentially serious health problems, including high blood pressure, heart disease, stroke, type 2 diabetes, sleep apnea, and certain cancers, among other problems.

The Relationship Between Psoriasis and Obesity

Research has established a clear association between psoriasis and obesity, including how the two conditions may influence each other and affect the severity and treatment of psoriasis.

Obesity and Psoriasis Onset

Although there is ongoing debate about the exact correlation between psoriasis and obesity, evidence suggests that the relationship is bidirectional: obesity may be a risk factor for psoriasis, or psoriasis may lead to obesity.

The association between psoriasis and obesity is believed to arise, in part, from the fact that both diseases involve chronic inflammatory processes. A network of inflammation-causing proteins known as cytokines, particularly tumor necrosis factor-alpha (TNF-α), is thought to play a key role in the development of obesity and psoriasis. In obesity, TNF-α is believed to come from certain inflammatory cells found in body fat, whereas in psoriasis, it’s thought to be derived from activated T cells (white blood cells that play a key role in the immune system).

Obesity is common in people with psoriatic disease (psoriasis and psoriatic arthritis, or PsA), and obesity is even more common in those with psoriasis alone.

Obesity and Psoriasis Severity

Obesity is not only a risk factor for developing psoriasis, but it also aggravates psoriasis in people already living with the disease. Research has indicated a positive correlation between different measures of body fat and the severity of psoriasis.

One 2017 study of 42 hospitalized individuals with psoriasis found that there was no significant relationship between BMI or waist size average and the severity of psoriasis. However, other research tells a different story. One 2015 review of psoriasis-related studies analyzed the relationship between psoriasis severity and obesity. Most of these studies used the Psoriasis Area and Severity Index to measure disease severity. According to the review, seven of the nine studies included found a statistically significant association between higher BMI and increased psoriasis severity. Obese or overweight individuals with psoriasis were more likely to have severe psoriasis requiring systemic therapy.

In the same vein, research has found that losing weight may improve psoriasis severity in those who are overweight.

Obesity and Psoriasis Treatment

Excess body weight may also interfere with the effectiveness of medical treatments used for psoriasis. Obesity is associated with lower retention and response rates to disease-modifying antirheumatic drugs (DMARDs). Obesity may also increase a person’s risk of renal (kidney) and liver toxicity while taking Trexall (methotrexate) and cyclosporine.

In people with obesity for whom psoriasis treatment isn’t very effective or safe, losing weight may help the psoriasis medications work better, research suggests.

Because of the relationship between obesity and psoriasis treatment, your dermatologist may encourage healthy lifestyle habits and weight loss if you have psoriasis and obesity. However, keep in mind that what may help one person may not work the same way for you. As one MyPsoriasisTeam member wrote, “I was obese for many years, and two years ago, I lost 80 pounds. My weight never affected my psoriasis. What does affect it is stress.”

Find Your Support System

Living with a chronic condition like psoriasis can be a challenge. But remember, you’re not alone.

MyPsoriasisTeam is the social network for people with psoriasis. Here, more than 89,000 members discuss the ins and outs of life with psoriasis, including their different health concerns alongside psoriasis. Join the conversation today by sharing your story in the comments below, or by creating a post on MyPsoriasisTeam.