system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Does using the brain burn any noticeable amount of calories, and if so, could you exercise mentally instead of physically?

How many calories does the brain burn and do different mental activities burn more calories than others?
gpt
The brain does consume plenty of calories (when you're resting, it's actually a pretty large part of your energy usage), but the difference between a resting brain and a thinking one is much, much smaller than the difference between a resting muscle and a working one.