system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why is it when I eat or drink some things I feel like pooping within a few minutes when food and drink take hours to digest?
gpt
Eating or drinking something kick your digestive tract into motion. Lots of enzymes start squirting into your intestines.  Lots of muscle contractions from your stomach to your butthole getting things moving along.  Some chemicals in food (caffeine in particular) are *really* stimulating to your intestinal muscles.  When those start working overtime, you suddenly get the urge to go, like, now.