Exclusive | NASA monitoring second stranded astronaut’s possible weight loss after raising alarm about colleague Sunita Williams’ health

NASA doctors are monitoring the second astronaut stranded on the International Space Station — and making sure that he isn’t losing too much weight during his extended stay in space.

A NASA employee who is involved in the mission told The Post that Butch Wilmore has also been losing body mass, although it doesn’t seem to be as pronounced as that of fellow astronaut Sunita Williams.

“He had a lot more mass at the start,” said the NASA insider, “so it’s not as big of a deal. But it’s happening, and it’s being monitored. Any changes in the astronauts’ bodies are being noted. And his mass seems to have gone down.”

Wilmore, 61, was a former linebacker at Tennessee Tech University. At approximately 6 feet tall, he weighed more than 210 lbs. at the start of the mission. It’s unclear how weight much he has lost.

“Everything is unexpected,” says the NASA employee. “None of this was anticipated. They were supposed to be there for a week, and now it’s going on six months. They should be home by now and we should be focused on other things. It’s all very unpredictable.”

The focus on the astronauts’ weight became public after NASA released photos that showed Williams, 59, appearing jarringly gaunt, with sunken cheeks and a noticeably thinner frame.

On Tuesday, Williams downplayed the concerns about her visible weight loss as “rumors,” and said her difference in appearance was the result of fluid shifting in her body due to the weightlessness of space.

“Folks in space, you know, their heads look a little bit bigger because the fluid evens out along the body,” she during a livestream.

Williams and Wilmore passed their pre-mission physicals before the space flight, and were only slated to be on the ISS for eight days.

But when their Boeing Starliner experienced technical malfunctions, they became stranded in space. They have now been gone for 160 days.

A SpaceX Crew Dragon capsule will give them a ride home — but it’s not due to return to Earth until February.

In a statement last week, NASA stressed that there’s nothing to worry about, and that they are not overly concerned about Williams’ weight loss.

“All NASA astronauts aboard the International Space Station undergo routine medical evaluations,” the statement reads.”They have dedicated flight surgeons monitoring them, and are in good health.”

Another NASA employee who is tangentially involved in the mission tells the Post that NASA has become concerned about the speculation — and are warning their employees that leaking sensitive information about the astronauts’ health could be grounds for firing.

“HIPAA laws apparently apply to NASA, too,” the employee says dryly.

Boeing, who suffered a public embarrassment when their Starliner malfunctioned, has been sidelined on the mission — but execs are closely watching the latest developments, according to employees. “If anything happens to those astronauts, heads will roll at Boeing,” says the employees. “This is a really, really bad look.”

The weight loss drama comes after a crew of four NASA astronauts returning to Earth on SpaceX’s Dragon capsule were rushed to the hospital after spending 200 days on the ISS.

One of those astronauts was kept overnight at Ascension Sacred Heart Pensacola Hospital, according to NASA.

The space agency did not reveal the nature of the medical emergency and the astronaut was released the following day.