The RiseFast pilot study will investigate the clinical, metabolic and immunological effects of fasting and plant-based diet (PBD) on patients with psoriasis (PsO) and psoriatic arthritis (PsA) on their gut microbiota. The project will combine clinical assessments, cytometric profiling, and gut microbiota analysis to explore the relationship between fasting, a plant-based diet, and psoriatic disease. The study includes a 7-day fasting period followed by 11 weeks of PBD, with the goal of improving disease activity, quality of life, and understanding the role of gut microbiota in these conditions. This approach could lead to low-cost, accessible therapeutic options with minimal side effects.