Background Long COVID (LC) is a chronic multisystemic condition which substantially impact the quality of life. Despite the staggering burden of LC, there is still no effective treatment.

Because fasting promotes anti-inflammatory and antioxidant responses, which are involved in the pathophysiology of LC, we hypothesized that it might improve daily functioning and health-related quality of life in patients with LC.

The aim of this single center, one arm, prospective pilot clinical trial will be to assess the feasibility and acceptability of prolonged fasting for LC. The main questions aims to answers are;

1. Does in-home prolonged fasting (7 days) is feasible and acceptable for patients with LC
2. Is there a clinical benefit associated with fasting is LC patients

Participants (adults 18 year and older) will be asked to

1. Fast for 7 days
2. Have in-person visit at baseline (day 0) and at day 9 for checkups and tests
3. Answer difference questionnnaires about their perceived health during and after fasting

Inclusion Criteria:

• Age 18-64 years
• Diagnosis Long Covid based on WHO criteria (post-acute COVID-19 symptoms persisting ≥12 weeks) and validiated by an experienced cinician
• Normal body Mass Index (18.5 to 39 kg/m2)
• Able to communicate in and comprehend English and/or French language
• Present written / signed declaration of consent
• Ability to understand the patient information and willingness to sign the consent form
• Willing to limit physical activity during prolonged fasting

Exclusion Criteria:

• Current underweight condition (body mass index less than 18.5 kg/m2) or weight loss exceeding 3 kg within the last month or 5 kg within the last three months.
• Current or history of eating disorder (e.g., anorexia, bulimia).
• Psychiatric condition that limits understanding of the examination protocol (unable to consent)
• Participation in another intervention study.
• Fasting during the last six months
• Pregnancy or breastfeeding status.
• Diagnosis of chronic inflammatory bowel diseases, celiac disease or colorectal cancer according to the guidelines of the Canadian Society of Gastroenterology
• Use of anti-psychotic drugs
• Start of novel drug therapy for long COVID
• Contraindication for additional blood draws (e.g. hemoglobin <100)
• Taking opioid analgesics or undergoing treatment for opioid addiction
• Opioid dependence or withdrawal syndrome
• Type 1 or 2 Diabetes, or history of hypoglycemia
• Active cancer
• Baseline E+ (Na, K, Mg, phosphate) within normal range
• Baseline ALT < 60
• Baseline Hb > 100
• Baseline INR within normal range
• Baseline DFG < 50

Except for the study protocol that we are willing to share, personal and confidential will not be shared