Chouji has never gone hungry. He is the heir to a fairly well-off clan, always more prone to overindulgence than deprivation. The intensity of his appreciation of food is due entirely to a mix of his clan's philosophy and techniques his own disposition. So while he values food highly, has more use for it than most, he would not understand Prim's view of it. Not through experience, at least.

"I haven't been here long enough to shrug things off yet, but that's what I've heard too. This is only the second time since I arrived." Unless you count the draft, but Chouji doesn't. That wasn't strange or incomprehensible. He was at war, like he was at war at home. The rules had shifted, and he didn't have the luxury of fighting for his own people and homeland, but Chouji still wanted to protect whoever he could here.

"You're newer than I am, then? How are you holding up?"