One thing I’m not seeing mentioned is the “spit bucket”. Like in wine tasting the stuff isn’t really being consumed. Actors getting full isn’t an issue. They’re discarding it between takes by spitting it out.

The reason they don’t genuinely eat most of the time is because of continuity. It’s practically impossible to keep making identical looking partially eaten plates of food if a line gets botched and needs to be redone. It just isn’t worth the trouble.

It’s different with something like Brad Pitt eating an apple. It doesn’t have to sit on a plate in front of the camera and it can be turned around and partially obscured by his hand to easily hide any previously taken bites and obscure more subtle details in the shape. It isn’t hard to get a replacement apple. Same with hot dogs or some smaller snack foods.