Body Composition, Not Just BMI, Matters in Psoriatic Disease

BOGOTÁ, Colombia — While obesity has been studied extensively in psoriasis and psoriatic arthritis (PsA), little is known about the role of body composition, or the specific location of fat deposition in and around organs and muscle, in these diseases.

At the Group for Research and Assessment of Psoriasis and Psoriatic Arthritis (GRAPPA) 2025 Annual Meeting and Trainee Symposium, two groups of researchers working with MRI and clinical data from the UK Biobank presented detailed findings that shed light on how different body composition profiles might influence or be influenced by psoriatic disease.

Visceral, Liver, and Muscle Fat Predict Disease

In a poster, Rheumatologist Jean-Guillaume Letarouilly, MD, PhD, of Lille University, Lille, France, and Oxford University, Oxford, England, showed results from a cross-sectional study of 841 patients with psoriasis, 125 patients with PsA, and about 34,000 nonpsoriatic control individuals. Patients across groups had a mean age of 64 years, were nearly all White, approximately half were women, and only a minority (17%-22% across groups) had a BMI ≥ 30. All patients underwent abdominal MRI scan, and participants with psoriasis or PsA were identified by self-report and primary care and hospital records.

In multivariate models, Letarouilly and his colleagues found that patients diagnosed with psoriasis tended to have significantly lower muscle volume, higher liver fat, higher visceral fat, higher muscle fat infiltration, and higher total abdominal fat than control individuals without psoriasis. Patients diagnosed with PsA, meanwhile, tended to have significantly elevated liver fat, higher muscle fat infiltration, and higher abdominal fat (but not visceral fat) than control individuals without PsA. The results were suggestive of “a potential impact of the inflammatory burden of the psoriatic disease on the body composition,” the investigators concluded.

In an interview at the meeting, Letarouilly cautioned that his findings “are for the moment just descriptive. What we need to do now is determine in a longitudinal way whether these body composition changes appear before the disease itself and what role these different types of body fat play in the [pathologic] process.”

Lower Muscle Volume, More Intramuscular Fat Linked to Psoriasis Risk, Comorbidities

At the same meeting, Lyn Ferguson, MBChB, PhD, of the University of Glasgow, Glasgow, Scotland, presented results from a different body composition study using UK Biobank data. Ferguson compared results for 236 patients with psoriasis and 1180 control individuals matched for age (mean of about 66 years), sex (about 51% women), and BMI (about 27) — all variables that can affect body fat distribution. She also identified 61 patients with PsA and 305 matched control individuals, both of whom had a mean age of about 63 years, 49% were women, and BMI of about 27. None of the control individuals had metabolic or cardiovascular disease at the time of their baseline scans.

Ferguson aimed to determine not only whether people with psoriasis and PsA are more likely to have certain body composition profiles but also whether the same measures of body composition — liver fat, visceral fat, and muscle quality — could also predict diabetes and coronary heart disease in these patients.

Ferguson found that people with psoriasis had significantly more fat around the organs (visceral), in the liver, and in muscle, whereas people with PsA had significantly more fat in the liver and muscle than age-, sex-, and BMI-matched control individuals. These body composition profiles were significantly associated with greater propensity to type 2 diabetes. “We know from the clinic that patients with psoriatic disease have a greater prevalence of diabetes,” Ferguson said in an interview at the meeting. “This could be in part related to the fat distribution pattern in psoriasis and PsA.”

The Surprising Importance of Muscle 

Ferguson noted that about half of people with psoriasis or PsA had either low muscle volume, high muscle fat, or both — a state known as adverse muscle composition. In individuals with psoriatic disease, adverse muscle composition was associated with over double the propensity to coronary heart disease and three times the propensity to type 2 diabetes compared with a normal muscle composition.

Ferguson said a provocative finding from her study was that poor muscle quality was also associated with more than double the risk for new-onset psoriasis (adjusted hazard ratio, 2.12; 95% CI, 1.29-3.50). “Having more fat stored in the muscle and lower muscle volume appears to be associated with greater risk of developing psoriasis. Whether this may relate to muscle fat being potentially more pro-inflammatory, or whether immune-metabolic dysregulation is already present and contributing to more fat in the muscle and muscle loss, is unknown and warrants further study.”

At a meeting intensely focused on the potential benefits of GLP-1 receptor agonists (RAs) in psoriatic disease, both Ferguson and Letarouilly said the muscle-quality findings were of special concern to them as physicians.

“It’s really important that people stay physically active to maintain muscle quality, especially if you’re losing a lot of weight” because of using GLP-1 RAs, Ferguson said. With the profound weight loss from this drug class, “a significant amount of weight loss could be muscle. And we’ve identified a group that has lower thigh muscle volume. That’s something we have to watch.”

Letarouilly added that stopping GLP-1 drugs has been reported to result in sarcopenic obesity, or concurrent muscle loss and fat gain. “That’s why it is important to advise people to do more exercise,” he said, adding that maintaining bone health is another, related concern. “We already see this with obesity surgery. With GLP-1s, we would need to monitor patients in the same way.”

Letarouilly had no disclosures. Ferguson disclosed receiving speaker fees from UCB and Janssen for talks on the role of obesity in psoriatic disease, and consultancy fees and conference travel from Sanofi unrelated to the current study.