Welcome! The first thing that springs to mind is a game based exactly on this premise, The SnackRooms. You could take inspiration from this, with the entities leaving food scattered around, perhaps fattening up their prey?
Or there could be some rival entities that want their victims to be fattened up in particular ways, leaving different foods out that would fatten different parts of the body. If one of those entities discovers the victims are eating their rival’s food, they could chase them away so that the victims both don’t eat that food, and any fat that they gained in “undesirable” areas would be burned off.
Not quite sure how I’d tie all of this into a conclusion, I can see multiple endings with this from the victims succumbing to either entity to the victims somehow managing to overpower the entities and fattening them instead, but not without a bit of “damage” along the way (It seems I’ve accidentally planned out a text adventure haha).
Kind of a weird plot I guess, but maybe there’s something useful in my ramblings lol.