LAUSR

Psoriasis affects 60 million people worldwide; 80% of them are either overweight or obese and at risk of developing weight-related comorbidities. Obesity increases susceptibility to psoriasis and is associated with more severe disease. In England, clinical guidelines recommend offering weight-management support for patients with psoriasis and obesity. Patients who attended our formative focus groups were unaware of the link between weight and psoriasis and desired evidence-based guidance on how weight management might improve their condition, but clinicians report a lack of evidence as a significant barrier to offering care. The aim of this study was to evaluate the impact of weight-loss interventions (lifestyle/behavioural and pharmacological) on psoriasis severity and quality of life. Psoriasis severity was measured using ≥ 50% and ≥ 75% reduction from baseline Psoriasis Area and Severity Index (PASI 50 and PASI 70, respectively), and quality of life was measured using Dermatology Life Quality Index. We conducted a systematic review of five databases and two trial registries from inception to 9 September 2024. Outcomes were informed by conversations with patient focus groups. Randomized controlled trials that compared any weight-loss intervention to usual care or a lower-intensity intervention for adults with psoriasis were included. Studies had to report weight change and at least one measure of psoriasis severity at baseline and follow-up. Data were analysed using a random effects meta-analysis. Risk of bias was assessed using the Cochrane tool (RoB2). Eleven randomized controlled trials (994 participants) with 12 comparisons were included. Ten interventions advised dietary changes (including low- and very-low-calorie diets, low-carbohydrate or low-fat diets, and total dietary replacement) with or without physical activity. Two offered pharmacological weight-loss agents (glucagon-like peptide-1 receptor agonists). Based on 11 comparisons (n = 732, mean weight change −6.3 kg), weight-loss interventions were associated with a greater reduction in psoriasis severity, compared with control, with a mean difference in PASI of −1.9 [95% confidence interval (CI) −3.1 to −0.8, P < 0.001, I2 = 72.1%]. Sensitivity analyses excluding studies at high risk of bias, where minimal weight loss was achieved or where baseline PASI was low, did not meaningfully modify the effect estimate. Based on five comparisons (n = 213, mean weight change −8.7 kg), there was no evidence that weight-loss interventions were associated with significant improvements in quality of life, with a pooled mean DLQI difference of −5.7 (95% CI −12.4 to 1.1, I2 = 95.9%). There was evidence of significant effects of weight-loss interventions on the likelihood of achieving PASI 75 (relative risk 1.6, 95% CI 1.1–2.2, I2 = 22.6%; based on six comparisons, n = 681, mean weight change −7.3 kg) and PASI 50 (relative risk 1.6, 95% CI 1.0–2.6, I2 = 0.0%; based on three comparisons, n = 389, mean weight change −4.9 kg). Various weight-loss interventions were associated with improvements in psoriasis severity and quality of life. This evidence should encourage clinicians to incorporate support for weight loss as part of routine care for people with psoriasis and obesity.