Toph can hear the rubble in your gut, see the change in how your intestines hang, and knows how close you are to your next poop. She never mentions this, but does use it to make well-timed "you're full of shit" jokes.
Still fucks me up that a very large amount of animals on this planet decided it's easier to just fuckin eat rocks than to learn how to chew their food.
And then we have shit like crocodiles and alligators that have stomach acid strong enough to dissolve an animal twice their size but split into like 5 whole pieces.