High-certainty evidence suggests weight-loss interventions improve psoriasis severity and quality of life in adults

BACKGROUND: Psoriasis affects at least 60 million people worldwide, and 80% also live with overweight or obesity. Excess weight increases susceptibility to psoriasis and is associated with more severe disease. OBJECTIVES: To evaluate the impact of weight-loss interventions on psoriasis severity (Psoriasis Area and Severity Index [PASI], PASI50, PASI75, PASI100 [50%/75%/100% reduction in baseline PASI, respectively]) and quality of life (Dermatology Life Quality Index [DLQI]). METHODS: We systematically searched five databases and two trial registries (inception to 03/09/2025). Outcomes were informed by patient focus-group discussions. Randomized controlled trials (RCTs) in adults with psoriasis, comparing any weight-loss intervention versus usual care or a lower-intensity weight-loss intervention, were included. Studies had to report a change in weight and ≥1 psoriasis severity or quality-of-life measure. Random effects meta-analyses were used. RESULTS: Thirteen RCTs (1145 participants) with 14 comparisons were included. Eleven interventions advised dietary changes, of which four included physical activity. Three used weight-loss medications. Across 14 comparisons (n = 1145, mean difference (MD) in weight change: -6.7 kg), weight-loss interventions produced a greater reduction in PASI versus control: MD -2.5 (95%CI: -3.8 to -1.1, I = 85.2%). We found a significant effect of weight-loss interventions on the likelihood of achieving PASI75 (RR = 1.6, 95%CI: 1.1-2.2, I = 22.6% [based on six comparisons, n = 681, MD in weight change: -7.3 kg]). There was no statistically significant effect of the interventions on the likelihood of achieving PASI50 (RR = 1.5, 95%CI: 0.9-2.4, I = 72.8% [based on four comparisons, n = 509, MD in weight change: -4.0 kg]) or PASI100 (RR = 1.6, 95%CI: 0.3-9.7, I = 0.0% [based on two comparisons, n = 334, MD in weight change: -5.2 kg]), but both analyses were limited by few studies. Across seven comparisons (n = 364; MD in weight change -7.8 kg), weight-loss interventions were associated with a significant improvement in DLQI compared to control: MD -5.0 (95%CI: -9.7 to -0.3, I = 96.0%). CONCLUSIONS: High-certainty evidence suggests weight-loss interventions can improve psoriasis severity and quality of life, and should be considered as part of routine treatment.