Why do astronauts need more calories in space

Astronauts in space require a higher calorie intake (2,500–3,800 daily) compared to those on Earth (2,000–2,500). Microgravity increases energy expenditure due to physiological adaptations, increased exercise to combat muscle and bone loss, and a higher basal metabolic rate. The body works harder to maintain basic functions, thermoregulate, and manage fluid shifts, all contributing to the elevated caloric needs.