Background: Long COVID, characterized by persistent symptoms following acute COVID-19 infection, has emerged as a significant public health concern. Symptoms range from fatigue, cognitive impairments, to respiratory difficulties, affecting patients\' quality of life. Dietary interventions, particularly fasting, have historically been used to modulate immune responses and improve health outcomes in various conditions. The Buchinger-Wilhelmi method represents a structured and medically supervised fasting approach. Given the inflammatory nature of long COVID, fasting may offer therapeutic benefits by modulating the immune response, enhancing cellular repair mechanisms, and resetting metabolic processes.

Objectives: This clinical trial aims to assess the feasibility of a 7-day ambulatory fasting intervention using the Buchinger-Wilhelmi method on long COVID patients as primary objective. As secondary objectives, the study will investigate the potential beneficial impact of fasting on clinical, biological, and psychological parameters over a period of 4 weeks, offering insights into potential therapeutic avenues for long COVID management. Study timeline: The research will span a period of 4 weeks Study population: This study aims to recruit around 20 participants, who will all receive a fasting intervention using the Buchinger-Wilhelmi method. Biological sample and data collection: Participants will undergo various data and sample collection procedures, including blood draws of up to 90 42 ml per visit, collection of peripheral mononuclear cells, stool samples, and completion of questionnaires in a smartphone-based Application (MyCap). Sample analysis: The collected samples will be subjected to a range of analyses, including the assessment of serological markers for routine blood chemistry, evaluation of inflammation markers, and examination of stool samples.