The Meta-SHIFT Study: How Metabolic Shift Shapes Human Immunometabolism - a Fasting Trial

Inclusion Criteria: * Apparently healthy * Age 18-40y at the time of recruitment * BMI ≥ 18.5 and ≤ 24.9 kg/m2 * Willing to participate in all study activities during the 3-day intervention * Signed informed consent Exclusion Criteria: * Diagnosed with any chronic medical condition that can interfere with the study outcome (e.g., cardiovascular disease, cancer, diabetes mellitus type 1 or 2, liver disease, pulmonary disease, renal disease, inflammatory bowel disease, thyroid disease, long COVID, PASC) * Bleeding disorder (e.g., Hemophilia A/B, Von Willebrand Disease, or low platelets), current anemia or current use of blood thinners or anticoagulants (e.g. warfarin, heparin) * Any acute or chronic infection disease or fever in the past month * Antibiotic use in the past 2 months * Use of any prescribed medications (incl. GLP-1 agonists), except for contraceptives * Usage of recreational drugs in the last three months * Unstable body weight (weight gain or loss \>5% of total BW in the past three months) * Following any restrictive diet within one month of starting the study (for example a ketogenic diet or weight loss diet) * Fasted for 16 hours or longer in the past week * History of an eating disorder (e.g., anorexia nervosa, bulimia nervosa, or binge eating disorder) * Allergic to one or more components of the standardized meal and/or shake (i.e., milk, wheat, and soy) * Average alcohol intake that exceeds 1 consumption/day or 7 consumptions/week over the past month * Tobacco smoker or regular use of nicotine products * Donated or intend to donate blood from 2 months before the study until the end of the study * Being pregnant or lactating * Participation in another biomedical study during this study