Obesity or Psoriasis: What Comes First?

Fabiano M. Serfaty, MD, MSc


November 24, 2021

Psoriasis is a polygenic chronic inflammatory skin disease. A large proportion (20%‑30%) of psoriasis patients suffer from joint involvement (psoriatic arthritis) that mainly affects the distal extremities but also attacks the larger joints.

Plaque-type psoriasis, the most common disease variant, is seen in ~85% of cases and commonly manifests as dull-red, erythematous, scaly plaques particularly on the extensor surfaces of the elbows, knees, and scalp. Less common psoriasis subtypes include pustular, guttate, inverse, erythrodermic, and palmoplantar.

In the current context of the COVID-19 pandemic, it is worth pointing out that even though the Centers for Disease Control and Prevention (CDC) still does not include individuals with psoriasis or other autoimmune diseases among those at high risk for COVID-19, many psoriasis patients present with associated comorbidities, such as obesity and diabetes, which put them at greater risk of getting severely ill, or dying, from COVID-19.

The close link between psoriasis and obesity is becoming more evident to physicians in their daily clinical practice. The scientific evidence is clear in regard to the bidirectional association between obesity and psoriasis: Obesity and overweight are associated with higher incidence of psoriasis, and people with psoriasis may be more prone to gaining weight.

The fat cells of individuals with overweight or obesity release inflammatory cytokines that play a role in the worsening of psoriasis symptoms. High levels of resistin and leptin have been found in psoriasis patients with obesity.

The incidence of psoriasis among adults had almost doubled between the 1970s and 2000, and because the genetic basis has not significantly changed, environmental factors — including lifestyle and diet — might have played a role in this growing prevalence. The dietary habits in industrialized nations often support foods and drinks high in carbohydrates, resulting in obesity and metabolic syndrome.

In a large Norwegian study with 35,000 subjects, an association of metabolic syndrome with an increased risk of developing psoriasis has been described.

In a separate paper on psoriasis, obesity and fatty acids, an analysis indicated that adiposity is a central factor in this association. Similar findings were reported in other studies.

It is difficult to know what comes first: psoriasis or obesity. Pronounced social isolation, poor eating habits, depression, increased alcohol consumption, and decreased physical activity in patients with psoriasis might explain in part how psoriasis could lead to obesity.

Epidemiologic studies, however, provide strong evidence that obesity predisposes patients to psoriasis and amplifies psoriatic inflammation. A study by Setty and coworkers, including 78,626 women (of whom 892 reported having psoriasis), indicated that adiposity and weight gain were risk factors for the development of psoriasis. Patients with a body mass index (BMI) of 35 or higher had a relative increased risk for development of psoriasis of 2.69 compared with lean patients.

And a prospective study from 2017 indicated that obesity and high abdominal fat mass doubled the risk for psoriasis. These studies suggest that preventing weight gain, promoting maintenance of a normal body weight, and reduction of body mass may reduce incidence of psoriasis. Indeed, several studies have showed a positive impact of weight loss on the severity of psoriasis, according to this 2018 review.

A multifactorial and personalized approach must be taken when treating psoriasis or any chronic disease. We should advise our psoriasis patients to lose weight, engage in physical exercise, and manage their comorbidities.

Losing weight reduces chronic inflammation; therefore, weight loss may decrease the severity of the patient's psoriasis as well as reduce the amount of skin involvement. In addition, weight loss may improve the effectiveness of medications used to treat psoriasis.

Getting down to, and maintaining, a healthy weight is beneficial for anyone, but especially for individuals who have chronic inflammatory diseases such as psoriasis.

It is important to remember that current global trends show an increasing prevalence of all chronic diseases (eg, obesity, cancer, heart conditions, and diabetes), and these will increase mortality both in developed and developing countries; therefore, any measures that can help to fight these chronic diseases are going to have positive effects the world over.

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