Doctor weighs in on stranded NASA astronaut Sunita Williams' weight loss 'rumors'

A doctor has raised more concerns about the health of a stranded NASA astronaut after she released a bizarre video addressing speculation about her weight. 

Sunita Williams, 59, broke her silence Tuesday to address weight loss 'rumors,' saying a 'fluid shift' caused by microgravity had made her head look bigger. 

During spaceflight, weightlessness instantly shifts blood and fluids from the lower portion of the body to the upper areas. 

But Dr David Shaker, an internist at Holy Name Physicians in Hackensack, New Jersey, told DailyMail.com that fluid shift likely wouldn't result in the 'decreased nutritional appearance' shown in recent photos.

Dr Shaker looked at several images of Williams from the ISS and said that she did not seem to have a healthy body weight.

'This, to me, strikes me as low nutrition - low-calorie intake,' he said.

Williams also proudly claimed that she packed on muscle during her 160-day stay, specifically in her thighs and buttocks. But Dr Shaker said: 'I would be surprised if that was the case.'

He suggested Williams' nutritional deficit could be the result of physiological symptoms of anxiety or depression due to her circumstances. But there has been no clear evidence to suggest that her mental health has been suffering.

Williams launched toward the ISS with her crewmate, NASA astronaut Barry Wilmore, on June 5 aboard Boeing's Starliner Spacecraft.

Their mission was only supposed to last 10 days, eight of which were to be spent on the ISS. But numerous technical issues with their faulty spacecraft have left them stuck up there until February 2025 at the earliest. 

Fears about Williams' health were sparked by an image from September, showing her with what Dr Vinay Gupta, a pulmonologist and veteran in Seattle, described as a 'gaunt' face and 'sunken cheeks.'

But NASA's chief health and medical officer Dr JD Polk told DailyMail.com: 'All NASA astronauts aboard the International Space Station are in good health. It's unfortunate that rumors persist otherwise.'

'NASA and our partners have safely conducted long-duration missions aboard the orbital laboratory for decades, studying the effects of space on the human body as we prepare for exploration farther into the solar system.'

'Crew health is regularly monitored by dedicated flight surgeons on Earth, and they have an individual diet and fitness regime to ensure they remain healthy throughout their expeditions.'

On Tuesday, Williams gave a live interview from the ISS, in which answered questions about her time living in space and also addressed fears about her health.

'I think there's some rumors around outside there that I'm losing weight and stuff. No, I'm actually right at the same amount,' she said.

'Things shift around quite a bit. You've probably heard of a fluid shift where folks in space - their heads look a little bit bigger because the fluid evens out along the body.'

She went on to say that her exercise routine has actually caused her to gain some muscle while on the ISS. 

'My thighs are a little bit bigger, my butt is a little bit bigger,' she said.  

But Williams' claims contradict what photos appear to show and what doctors know about how the human body is affected by the space station's environment. 

It is well-documented that astronauts tend to lose weight - particularly through loss of muscle and bone density - during long-term ISS missions.  

Dr Shaker explained that muscle groups in the legs and buttocks typically shrink in space because they are not constantly pushing against gravity.

Astronauts can lose between 10 and 20 percent of their body mass during short missions, and up to 50 percent during long missions, according to the European Space Agency.

Crew members exercise for an average of two hours per day to combat muscle and bone density loss, according to NASA.

'We've been on the workout gear,' Williams said in the video, referring to herself and her crewmate, Barry Wilmore.

'We've got a bike, we got a treadmill, and we got weightlifting equipment.'

'And I could definitely tell that weightlifting, which is not something I do all the time, has definitely changed me,' she said, adding that her thighs and butt have grown.

All of their exercise equipment is modified to counteract the effects of microgravity, allowing astronauts to get roughly the same strengthening benefits from working out that they would on Earth.

But all that exercise burns a lot of calories. Astronauts can burn up to 3,500 calories per day while living on the ISS, which means they need to consume a lot more food to maintain their weight than they do on Earth.

An unnamed NASA employee told the New York Post that Williams has been struggling to keep up with the high-caloric diets that astronauts must eat.

This is not uncommon on the ISS. Astronauts often struggle to meet their intense nutritional needs for several reasons.

For one, food can taste bland on the ISS because upward fluid shift can cause nasal congestion, which blocks astronauts' sense of taste.

Additionally, some astronauts suffer from motion sickness which causes them to lose their appetite.

And mental health can play a role in this too, Dr Shaker said.

He explained that spending months far away from her home and loved ones in an isolated, confined space could impact Williams' eating habits.

She has not said that she is suffering from anxiety or depression, but due to her current circumstances, she may be experiencing the physiological symptoms of these mental health conditions.

'We look at anxiety and depression as biochemicals,' said Dr Shaker.

'Even if you have quote-unquote mental toughness, you can still go through a physiologic depression where your mind is low on serotonin, low on dopamine, and that's a natural response to a stress state.'

'You have patients who are anxious and depressed who don't eat, because they have loss of appetite. They can't stomach food.' 

Despite Williams' assertion that she has not lost any weight while on the ISS, the anonymous NASA source told the New York Post that 'she has lost a lot of weight.' 

'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,' the source said, adding that she may have to eat up to 5,000 calories per day to get back on track.