Why do astronauts require significantly more energy than sedentary people on Earth regarding spirulina consumption?

Due to physical exertion in microgravity maneuvering and countermeasures against muscle atrophy.

Astronauts performing tasks in microgravity, such as maneuvering within the spacecraft or executing necessary physical countermeasures to combat muscle atrophy and bone density loss, require a substantially higher caloric expenditure compared to sedentary individuals on Earth. While spirulina is an excellent protein source, it lacks the high levels of carbohydrates and fats needed for this high energy demand. Consequently, spirulina serves as a nutritional foundation, but the overall diet must be supplemented heavily with other energy sources to meet the increased metabolic demands imposed by life in space.