system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do our body require so large an amount of energy to survive?

An average body use up 1500-2000 kcal just to keep the organs running. To put in perspective that's enough energy to boil 15-20l of water from 0 degree. So what processes require such an amount of fuel?
gpt
The biggest energy hogs are our muscles and brains. The electrical activity that powers both takes a huge amount of energy. Our nerves force ions together against the natural arrangement, generating an electric differential (like compressing a spring). When the nerve fires, the differential is released, but it has to be set back up again. Your muscles also need energy to move and repair themselves. 

However, the biggest energy hog of all is our warmblooded nature. We need a constant body temperature, but we radiate excess heat to the air, so we need to burn Calories to maintain our temperature.