NASA doctors are frantically trying to help stranded astronaut Sunita Williams pack on the pounds after she has suffered a “significant” weight loss since arriving at the International Space Station in June.

Newly released photos show Williams, 59, appearing jarringly gaunt, with sunken cheeks and a noticeably thinner frame.

“She has lost a lot of weight,” said a NASA employee who is directly involved in the mission and has attended multiple briefings.

“The pounds have melted off her and she’s now skin and bones. So it’s a priority to help her stabilize the weight loss and hopefully reverse it.”

Williams and fellow astronaut Barry 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.

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

They have now been in space for 155 days.

According to the NASA source, the 5-foot-8 Williams began the mission at approximately 140 lbs.

But as the mission dragged on, Williams was unable to keep up with the high-caloric diets that astronauts must consume, the source said.

Due to changes in their metabolisms, astronauts have eat twice as many calories as earthbound humans need each day.

“They have to eat about 3,500 to 4,000 calories per day, just to maintain their current weight,” said the NASA employee.

“And when you start falling behind, your weight drops fast.”

Adding to the issue: They must also exercise for more than two hours each day to maintain their muscle mass and bone density in a zero-G environment, burning even more calories.

Williams, an avid runner, became the first person to run a marathon in space in 2007 by running along with the Boston Marathon on a treadmill.

To put on weight, Williams could have to eat up to 5,000 daily calories, the source said.

The average woman on Earth needs approximately 1,600 to 2,400 calories to maintain their weight.

NASA doctors started working with Williams about a month ago to help her pack on the pounds — even before the viral images caused global concern about her health, the source said.

Several NASA studies have determined that the effects of space travel are harsher on women. A 2023 study found that female astronauts lose muscle at a faster rate than their male counterparts.

But in a statement on Thursday, 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.”

The alarming photo 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.

Speculation of Williams’ health has become fodder for gossip around NASA, said the source.

“I gasped out loud when I saw the last picture,” the NASA employee said.

“And it’s something we’re talking about, but not something we’re obsessing about. It’s a real concern and everyone is taking it seriously.”