I have a pet that no matter how much I've fed him his stat doesn't change. He's just always hungry and depressed.

I also adopted one and she is the same.

Is there a way to change this without giving them away?

Subeta pets get full slowly it seems.

Try putting them in the Lakeview Resort and giving them each a minion.

It takes about 8-10 pieces of food to go from Starving to Bloated.