BRAHMS: 10 French men simulate weightlessness for MEDES and CNES in Toulouse

Confined to bed and put on an extremely strict diet.

Last month, ten French men aged between 20 and 40 took part in an extraordinary trial. They were recruited for a scientific study simulating weightlessness, run in Toulouse by the Institute of Space Medicine and Physiology (MEDES) on behalf of CNES. After volunteers were sought in February, the BRAHMS study (Bed Rest and Hypometabolism Study) took place in June at Toulouse University Hospital (CHU) Rangueil.

For around 20 days, the ten participants agreed to help push research forward. While they got a small taste of what astronauts live through, the reality was far from enjoyable: they spent several days in bed while following a very tightly controlled diet capped at 250 kcal per day.

MEDES and CNES: simulating weightlessness under extreme calorie restriction

In its Toulouse-based “space clinic”, MEDES is examining what happens when severe calorie restriction is combined with weightlessness simulated through bed rest. The goal was to recreate, as closely as possible, conditions that astronauts might face on a mission-particularly if a resupply attempt fails and a prolonged period of fasting becomes unavoidable. BRAHMS is intended to help prepare future space flights and to anticipate unforeseen situations in orbit.

Like an astronaut…

The ten male volunteers selected for the study went through 21 highly unusual days, supported by 12 French scientific teams. First came five days of tests to establish baseline measurements.

The BRAHMS protocol: 21 days, 250 kcal per day, and a 6° head-down tilt

Then came the central phase of the research: ten days of strict bed rest, with permission to consume only 250 kcal per day-around 10% of the recommended daily intake. In practice, their daily “menu” amounted to a single spoonful of honey, a fruit juice and a broth, all while they remained in bed in a 6-degree head-down position to simulate microgravity.

This set-up is designed to reproduce key effects of microgravity, including the redistribution of bodily fluids, loss of muscle and bone mass, and cardiovascular as well as cognitive changes.

Naturally, the volunteers did not return home straight after these ten demanding days. MEDES kept them for a further five days to recover under medical supervision.

Now that the study has finished, the volunteers will have a medical follow-up in three months to ensure everything remains fine. Although BRAHMS is a single study, it is comparable to running a dozen clinical studies at the same time.

Recruitment: 7,500 applications for 10 places

Even though MEDES needed only ten men in perfect health, aged 20 to 40, the Institute received more than 7,500 applications. To encourage participation in such a demanding protocol, those selected received compensation of 200 euros.