BRAHMS: Bed Rest And HypoMetabolism Study

The goal of this single arm, interventional monocentric clinical trial is to investigate the physiological effects of a combination of head-down bedrest and caloric restriction on the human body. A set of measurements will assess the changes in the musculoskeletal, cardiovascular, hematological, immune, neurological, cognitive and metabolic systems, in 10 healthy male volunteers. The main question it aims to answer is: what are the physiological responses to fasting in a microgravity environment? In an exploratory study such as this one, where many physiological systems are explored, it is difficult to select a single important endpoint. However, given the known effect of both caloric restriction and head-down bedrest on muscle loss, and its critical importance for the success of space missions, lean body mass, as assessed by DEXA, was chosen as the primary endpoint. The secondary endpoints are: * Cardiovascular, muscular, neuro-vestibular and neuropsychological functional performance * The onset of clinical symptoms and biological changes Participants will be exposed to a microgravity analog model (head down bed rest) and controled caloric restriction environment for 10 days, multiple physiological assessments will be performed during this period. Followed by a rehab period before leaving the study.

NCT Number	NCT07499167
Lead Sponsor	Centre National d'Etudes Spatiales Collaborators: MEDES Institut de Médecine et de Physiologie Spatiales, Toulouse
Conditions	Microgravity, Caloric Restriction
Enrollment	10 participants
Start Date	2026-03-10
Primary Completion	2026-09-28 (estimated)
Study Completion	2027-09-28 (estimated)
Updated on ClinicalTrials.gov	2026-07-10