system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How does fiber make you have a better bowel movement?
gpt
Your body is very inefficient/incapable of breaking down the fibers. So they pass through your body and collect/soak up some of the bile from your guts and then it acts as lubrication for your bms.

Too much fiber also acts as a sort of (delayed) laxative, which will cause you to shit your brains out. So don't eat a whole box of fiber one in one sitting on a lady Sunday morning.