1.
When you ~ your food, you eat all of it.
Eat up your lunch...
Some seed fell along the footpath, and the birds came and ate it up.
PHRASAL VERB: V P n (not pron), V n P
2.
If something eats up money, time, or resources, it uses them or consumes them in great quantities.
Health insurance costs are eating up his income.
PHRASAL VERB: V P n (not pron)