“We found that astronauts had significantly less fat in their bone marrow about a month after returning to Earth,” said senior study author Dr Guy Trudel. “We think the body is using this fat to help replace red blood cells and rebuild bone that has been lost during space travel.”

Previous research from the same team showed that in space astronauts’ bodies destroyed on average 54 per cent more red blood cells than they normally would on Earth, resulting in what is known as “space anaemia.”

“Thankfully, anaemia isn’t a problem in space when your body is weightless, but when landing on Earth and potentially on other planets or moons with gravity, anaemia would affect energy, endurance and strength and could threaten mission objectives,” Trudel added.

The new study involved MRI scans of the astronauts’ bone marrow at multiple time points before and after a six-month mission at the International Space Station.

The researchers found a 4.2 per cent decrease...