People with psoriasis, a chronic inflammatory skin condition, are at risk of developing a related joint disease called psoriatic arthritis. Carrying excess weight is known to increase that risk, but it has been unclear whether losing weight after a psoriasis diagnosis can reduce it.

We studied 10,721 patients with psoriasis seen at UCLA, of whom 1,032 went on to develop psoriatic arthritis. We found that patients who lost at least 5% of their body weight in the year following their psoriasis diagnosis had a 37% lower risk of developing psoriatic arthritis compared to those who did not. Importantly, the more weight patients lost, the lower their risk, a pattern that held across every weight-loss threshold we examined.

We also found that patients who kept the weight off through two years had an even greater reduction in risk, suggesting that maintaining weight loss over time may matter as much as losing it in the first place.

Finally, we examined whether GLP-1 receptor agonists, a class of weight-loss and diabetes medications that includes drugs like Ozempic and Wegovy, reduced psoriatic arthritis risk beyond what weight loss alone would explain. We did not find a significant independent effect, but our study was not large enough to answer this question definitively. We plan to study a much larger group of patients across the University of California system to address this.