Playing chapter 2+3 again, I'm starting to question if Kris is actually falling apart/feeling lethargic purely because of this notion that he can't live without us or if there's a simpler reason than that. 3 and 4 all happen effectively on one day and 2 happens the previous afternoon if I got the timeline right.

I think it's as simple as (You) are starving him because we don't feel his hunger and aren't aware that he's starving. Susie is eating almost every actual piece of food in the game. Kris, if you add everything up, eats a bite of pancakes, maybe Darkner food but that's entirely optional and we're not sure that's "real", and a glass of chocolate milk. That's less than 600 real calories for two days. If the game's purpose is to change the way (We) treat Kris, then there could be hidden interaction with food in the Light World that the game is keeping track of that will become important later to keep Kris from passing out.