NASA's Anil Menon just shared that he lost 2kg during his time on the International Space Station, a pretty normal side effect of living in microgravity.
Astronauts often lose around 10% of their body mass during the first two weeks in space, but often regain some later.
Menon's update gives us a real look at how space changes the human body.
Spring device measures astronaut mass
Since regular scales don't work in space, astronauts use a spring-based device that measures mass by how quickly they move back and forth when strapped in.
It might sound odd, but it helps NASA keep tabs on astronaut health and figure out ways to protect future crews, especially for longer journeys beyond Earth.