There’s a couple with this concept, like Reindeer gains by ImpossibleSnail if you don’t mind Male and Furry where a reindeer eats Christmas snacks while avoiding coal. Reindeer Gains! Snailofapproval's submission
There was also this game on Furaffinity where you were a fish person in the ocean eating other fish people to gain weight and muscles, again Male and Furry, but I think it was only on Flash, so it might not be playable anymore.
Edit: Oh yeah, there’s a 3d first person perspective version of this concept called Chocoland where you play a lady that shows up in a Simpsons Dream Sequence and eats everything until she’s Kaiju sized. ChocoLand (Update 5: probably final major update)