1.
When you eat up 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)