Avoid using 'fill up on' when describing eating a meal. It usually implies eating only a part of a meal or snack. I filled up on appetizers and had no room for the main course.
Pro Tip 2/3
Avoid Overeating
'Fill up on' can carry a negative connotation, suggesting excess or lack of self-control in eating. She advised her kids not to fill up on sweets at the party.
Pro Tip 3/3
Casual Contexts
Best used in informal or casual situations, not in formal writing or speeches. At the picnic, we all filled up on grandma's homemade cookies.