BRAHMS study: 10 French men on 250 kcal/day bed rest at MEDES Toulouse

Confined to bed and kept on an exceptionally strict diet.

Last month, ten French volunteers aged between 20 and 40 took part in an unusual experiment. They joined a scientific study simulating weightlessness, run by Toulouse’s Institute of Space Medicine and Physiology (MEDES) for CNES. After a call for volunteers launched in February, the BRAHMS study (Bed Rest and HypoMetabolisme Study) was carried out in June at CHU Toulouse Rangueil.

For roughly twenty days, 10 men agreed to take part in order to help move research forward. Although they were able to “sample” a small part of astronauts’ lives, the experience was anything but enjoyable: they spent several days in bed while following a tightly controlled eating plan capped at just 250 kcal per day.

BRAHMS study at MEDES Toulouse for CNES

At the Toulouse space clinic, researchers are examining what happens when severe calorie restriction is combined with simulated weightlessness through bed rest. The aim was to mirror, as closely as possible, the conditions of crewed space missions, where astronauts could face extended periods without food after a resupply failure. Through BRAHMS, the objective is to better prepare for future spaceflights and to anticipate unexpected situations that may arise in space.

Like an astronaut…

The 10 male volunteers chosen for the project went through 21 highly unusual days. Supported by 12 French scientific teams, they first completed 5 days of tests to establish baseline measurements.

The central phase of the study followed: 10 days of strict bed rest with an allowance of only 250 kcal per day, which is 10% of the recommended daily intake. In practice, their daily “treat” amounted to a single spoonful of honey, a fruit juice and a broth-while remaining in bed with their heads tilted down at -6 degrees (to simulate microgravity).

This set-up helps reproduce key effects linked to microgravity, including shifts in body fluids, muscle and bone loss, and cardiovascular and cognitive changes.

Recovery, monitoring and recruitment

Naturally, the volunteers did not go straight home after those 10 demanding days. MEDES kept them for a further 5 days of recovery under medical supervision.

Now that the study has ended, participants will receive a medical follow-up in three months to ensure everything is fine. While it is a single study, it is equivalent to around a dozen clinical trials running at the same time.

Although MEDES only needed 10 perfectly healthy men aged between 20 and 40, the Institute received more than 7,500 applications. To encourage people to commit to such a demanding protocol, participants were paid compensation of 200 euros.