NASA is closely monitoring astronaut Sunita Williams’ health after she experienced significant weight loss during her extended mission on the International Space Station (ISS) with fellow astronaut Butch Wilmore.

What was originally intended to be an eight-day mission has now extended beyond 150 days due to technical issues with the Boeing Starliner, which returned without the crew. Recent images of Williams, showing her noticeably gaunt appearance, have raised concerns about the effects of long-term space travel.

A NASA source informed the New York Post that Williams’ condition has become a serious concern, noting she has “lost a lot of weight” and now appears “skin and bones.” Stabilizing her weight is now a priority for the agency. “I gasped when I saw the latest photo,” the source remarked, highlighting the seriousness of the situation.

At the start of her mission, Williams weighed about 140 lbs, but she has struggled to consume the daily 3,500 to 4,000 calories needed to meet the physical demands of living in space. “When you start falling behind on calories, your weight drops fast,” the NASA employee explained. This challenge is compounded by the requirement for over two hours of daily exercise to maintain muscle and bone mass in a weightless environment, which further increases caloric expenditure.

NASA doctors have been addressing Williams’ weight loss for more than a month, noting that female astronauts may experience muscle loss more rapidly than their male counterparts due to metabolic changes in space. According to a NASA physician, Williams’ appearance reflects “the natural stresses of living at high altitudes, even in a pressurized cabin for extended periods.”

A NASA spokesperson reassured the public, stating that all ISS astronauts receive regular health evaluations. “They have dedicated flight surgeons monitoring them and are in good health,” the spokesperson said, aiming to ease concerns as Williams continues her mission.