I assume people are genuine when they make that offer. I don't clear out their pantry, of course, but making myself something small like a bowl of cereal or toast hardly seems like an imposition. And if they aren't genuine, that's not actually my problem. They can communicate honestly with me next time, if it's really such a burden.

But it seems unfathomably rude to me, to expect a guest to skip a meal! What kind of host wouldn't feed their guests? Or would secretly hope for a guest to starve themself, so they wouldn't have to extend their hospitality? How heartless!