Why do astronauts have a 3,500-calorie diet in space?

Astronauts require 2,500 to 3,500 calories daily to compensate for the effects of microgravity, which causes muscle and bone loss, and changes in metabolism. Their intense exercise routines, crucial for maintaining physical health, further increase caloric needs. The ISS menu includes 50% carbohydrates, 17% protein, and 31% fat to maintain astronaut well-being during long missions.