Astronauts consume more calories in space than on earth. But, in her recently shared video Sunita Williams, looked to have lost considerable weight while working at ISS. In the clip, released by NASA, however she confesses that she is measuring the same body weight when she started the mission. "Things shift around quite a bit. You probably heard of a fluid shift in which folks in space, their heads look a bit bigger because the fluid evens out along the body," she said in the video. How Many Calories Do Astronauts Need In Space?All astronauts generally require 2,500 to 3,800 calories everyday, depending on their workload. Under the influence of microgravity, their body changes shape and thus, they tend to lose muscle and bone weight. Additionally, changes in metabolism and rigorous exercise routines can impact their weight. Caloric needs may also fluctuate based on mission demands, stressing the need for adaptable dietary strategies to maintain astronaut health and performance. According to the European Space Agency, astronauts have to exercise for at least two hours a day, six days a week to avoid quick muscle loss and bone loss in space.Astronauts Get Maximum Calories From Prepacked FoodSince they need higher calories than on earth, two thirds of calorie intake comes from the basic food supply that are preselected and prepared by NASA for their entire space mission. The menu on International Space Station (ISS) provides around 50% of calories as carbohydrate, 17% as protein, and 31% as fat. Sunita Williams and her colleague Barry 'Butch' Wilmore are set to return to Earth on SpaceX's Crew-9 Dragon capsule not before February 2025.What Does NASA Pack For Its Astronauts? The prepacked are prepared carefully to boost longetivity. Rehydratable foods, such as soups and casseroles, are created through freeze-drying or spray-drying processes. Thermostabilized foods, like Japanese curry or yakitori, are ready-to-eat or can be warmed onboard. Irradiated foods, including meats and dairy, undergo ionizing radiation to extend shelf life and prevent microbial contamination. The packaging also contain intermediate moisture foods retain some water, offering a soft texture. Lastly, natural form foods, like nuts and chocolate bars, are packaged for immediate consumption, combining simplicity with nutrition.ALSO READ: This 6-Letter Winter Fruit Is Great To Lower Blood Pressure And Blood SugarWhat Does Science Say? Maintaining bone and in fact, overall health in zero gravity requires a combination of rigorous physical activity along with good nutritional support. A study published in the Journal of Bone and Mineral Research demonstrated that heavy resistive exercise, combined with adequate intake of energy, protein, and vitamin D, is essential to preserve bone mineral density during extended space missions. The study highlighted the effectiveness of this approach after six months in a microgravity environment.A separate 2023 NASA study further revealed the significant risks astronauts face if precautions aren't taken. Without countermeasures, weight-bearing bones lose approximately 1% of their density for every month spent in space, underscoring the critical need for targeted interventions to mitigate this loss. ALSO READ: 7 Power-Packed Protein Shakes For Muscle Building And Bulking