system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How does your body burn 2000 calories a day, but you have to run a mile to burn 100 extra?

Basically the title. I saw this thing about how much you have to exercise to burn off certain foods and was wondering how your body burns so many calories by doing nothing.
gpt
You're not doing nothing.  Your heart is beating, your brain is processing, your eyes and ears are collecting information, your muscle tissue is idling, awaiting command.  You're maintaining a core temp of precisely 98.6F.

None of this is free, you'll consume 1500-2500 calories a day simply keeping the biological lights on.

We're highly efficient runners, and burn little energy to do so compared to many other animals.