Fasting or a Fasting Mimicking diet (FMD) can lower blood concentration of glucose and IGF1. Since cancer cells rely mostly on a glucose-based metabolism, FMD renders cancer cells more vulnerable to chemotherapy, thereby enhancing therapeutic efficacy. This process is known as differential stress sensitization (DSS). Another response to nutritional stress by fasting is known as differential stress resistance (DSR). DSR is a state in which healthy cells rather focus resources on protection and internal repair, which can result in reduced chemotherapeutic toxicity. Recent preclinical studies found that fasting or FMD not only aids healthy cell protection, but also has the potential to benefit effector T-cells and could thereby improve antitumor immunity. However in most oncotherapeutic clinical trials investigating the addition of a fasting regimen, other factors such as chemotherapy, surgery and additional medication affect the immune system as well. That is why this explorative study, conducted in healthy subjects, might be more suitable to investigate the immunological alterations upon FMD more specifically. This exploratory study aims to identify immunological alterations by using extensive immunoprofiling before and after three days of FMD in healthy subjects, as well as investigate possible side effects of FMD.

Inclusion Criteria:

• ≥18 years old
• BMI ≥18.5 and ≤25kg/m2

Exclusion Criteria:

• Chronic disease or active infection
• Medication use other than contraceptive, during the last 12 weeks prior to inclusion.
• A history of allergy
• Blood or plasma donation in the last 12 weeks prior to inclusion.
• Participation in other medical research in the last 12 weeks prior to inclusion.