Lying down for science: how 10 days of bed rest and fasting could help astronauts

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: * Healthy male volunteers (see below the description of medical tests and laboratory analysis performed at the selection visit) * Certified as healthy by a comprehensive clinical assessment (detailed medical history and complete physical examination): in particular, free from any known chronic disease or any acute mood or eating disorder, infectious disease or cardiovascular, metabolic, neurological, ENT (especially orthostatic hypotension and vestibular disorders), orthopedic or musculoskeletal disorders. * 20 to 40 years old * 165 to 185 cm * Body Mass Index between 20 and 26 kg.m-2 * Stable body weight in the past 3 months (less than 4% change) * Fat Mass Index (FMI), defined as (bodyfat weigh in kg)/(height in m)2: between 3 and 6 kg.m-2, measured by whole-body DEXA * Triglyceride level under 1.7 mmol.L-1 * Normal bone mass density at left hip and lumbar spine: T-score\>-1.5, measured by DEXA * VO2peak/VO2max between 35 and 55 mL.min-1.kg-1 * Non-smokers * No alcohol or drug dependence, no medical treatment on a regular basis * Affiliated to a Social Security system and, for non-French resident, holding a European Health Insurance Card (EHIC) or a Global Health Insurance Card (GHIC). * Free of any engagement during the study * Who agreed to take part in the study and signed the informed consent Exclusion Criteria: * Any history or presence of clinically relevant chronic disease; any acute infectious disease. Particularly (but not limited to): * Symptomatic orthostatic hypotension whatever the decrease in blood pressure, or asymptomatic postural hypotension defined by a decrease in SBP equal to or greater than 20 mmHg within 3 minutes when changing from the supine to the standing position * Personal or family history of thrombosis, genetic mutation for factor V or prothrombin gene * Cardiac arrhythmia * Hypertension * Auto-immune diseases or Raynaud's syndrome * History or symptoms of sleep apnea * Chronic back pains, * Vertebral fracture, scoliosis, or herniated disc, * Color-blindness, * Self-reported hearing problems or binocular visual acuity under 6/10 after correction * Vestibular disorders * Drug addiction * History of migraines, * History of hiatus hernia or gastro-esophageal reflux, * History of thyroid dysfunction or diabetes * History of head trauma, * History of neurological diseases (e.g. epilepsy) * History of genetic muscle and bone diseases of any kind * Significant history of allergies * Significant abnormality in blood tests * Positive serology for hepatitis A, hepatitis B, hepatitis C or AIDS (HIV) virus * Mood and Eating disorder (current or past), screened with the Hospital Anxiety Depression Scale (HADS), SCOFF (Sick, Control, One, Fat, Food) and the Eating Disorder Examination Questionnaire (EDE-Q) * Antibiotics exposure 2 months prior to the study * Major lifestyle changes (e.g. significant weight/body changes, diet or exercises regimen) 6 months prior to the study * Specific diet (e.g vegan, carnivore, intermittent fasting, dietary supplements consumption) * History of hypocaloric diet, judged as significant by the investigator * Subject who, in the judgment of the investigator, is likely to be non-compliant during the study, or unable to cooperate because of a language problem or poor mental development, * Subject in the exclusion period of another clinical research, * Subject who received 6000 Euros or more within 12 months for being a research subject, * Poor tolerance to blood sampling, * Subject who cannot be contacted in case of emergency, * Contraindications for MRI: claustrophobia, presence of osteosynthesis material or metal implants, * Blood donation of more than 7 ml/kg in the 8 weeks prior to the start of the study, * Vulnerable people according to law "Code de la Santé Publique" (L1121-5 to L1121-8): * Pregnant or nursing women (urine pregnancy test for women of childbearing potential) * People deprived of their liberty by an administrative or judicial decision * People under involuntary psychiatric care * People admitted in a health or social establishment for purposes other than research * Minors * Adults subject to legal protection (subject under guardianship or trusteeship) or unable to express their consent