Indian-origin astronaut Sunita Williams’ recent update to the International Space Station in which she appeared to have lost significant weight has been dismissed by NASA, saying “all (astronauts) are in good health.”

In a video released by NASA, she said she measured the same body weight as when she started the mission. “Things change a lot,” Williams said. “You’ve probably heard about fluid changes in which the heads of people in space look a little bigger because the fluids become homogeneous with the body,” Williams said.

She said she has been lifting weights and using a treadmill to maintain her weight and muscle.

Speculation about Williams’ health highlights the complexities of calorie requirements in space. While astronauts typically require 2,500 to 3,800 calories per day depending on their workload, factors such as microgravity-induced muscle and bone loss, changes in metabolism, and rigorous exercise routines can affect their weight.

Calorie needs may also fluctuate depending on mission demands, emphasizing the need for adaptable dietary strategies to maintain astronaut health and performance.

During long-duration space missions, diet plays an important role in maintaining physical and mental well-being. According to the European Space Agency, astronauts have to exercise at least two hours a day, six days a week, to avoid rapid muscle loss and bone loss in space.

Since they require more calories than Earth, two-thirds of these calories come from basic food supplies that are pre-selected and prepared by NASA for the entire space mission.

The International Space Station menu provides approximately 50% of calories as carbohydrates, 17% as protein, and 31% as fat.

A study in the Journal of Bone and Mineral Research that used heavy resistance exercise as a countermeasure to bone loss showed that adequate energy, protein, and vitamins were sufficient to maintain bone mineral density after a 6-month space flight. Supply of D is mandatory.

2023 A NASA study revealed that for every month in space, astronauts’ weight-bearing bones become about 1% less dense if they do not take precautions to counter this loss.

Sunita Williams and her colleague Barry ‘Butch’ Wilmore are set to return to Earth aboard SpaceX’s Crew-9 Dragon capsule no later than February 2025.