Mr Kanai tweeted: "Good morning, everybody". "We had our bodies measured after reaching space, and wow, wow, wow, I had actually grown by as much as 9 centimetres (3.5 inches)!"
He has taken to Twitter to express concern he won't fit in the Russian Soyuz vehicle set to take him home in June. His initial measurement was so extreme that he anxious he'd be too big for the tight space, which contains seat liners custom-molded for each astronaut and can not fit anyone above 6 feet, 3 inches tall.
A Soyuz-FG rocket booster with a Soyuz MS-07 spaceship carrying a new crew to the International Space Station blasts off at the Russian-leased Baikonur cosmodrome in Kazakhstan, on Sunday, Dec. 17, 2017.
Yes. Lt Kanai, 41, is a Japanese doctor selected as an astronaut candidate by the Japan Aerospace Exploration Agency (JAXA) in 2009.
As he puts it, he went "from deep sea to space".
NASA scientists say astronauts can grow up to three percent taller while in space or around five centimetres for someone 1.8 metres high.
NASA says that most astronauts grow by up to 3% during stints on the Space Station, in an example of, 'f how microgravity affects our bodies. Astronauts get taller in space because the absence of gravity allows the vertebrae in their spines to spread apart.
And when astronauts return to earth, so too do they return to their usual height.
When asked if Kanai should be concerned about making it back to Earth, Anderson said he is not anxious because once you return to Earth your spine shrinks back to normal. She told BBC News.
Thankfully, with a growth of only two centimetres, he would be well below the 191-centimetre limit.
"There's a range of growth for different people, and everybody responds differently".
Kanai will be landing back on Earth in a Soyuz spacecraft within the next six months. He'd have to grow more than another 9cm for his height to become a problem. This time round he was just less than an inch taller than originally believed.