I can't really say anything about how realistic the consumption is in terms of numbers, as the game is quite abstract about it. Satiety is not directly related to kcal, I think.
You're absolutely right with the bread. It's kinda ridiculus that you have to consume 5 loafs of bread (yielding 300 sat each) to fill your hunger bar. Despite that, it's not that unrealistic. A good meal can fill you up a lot. If done right, it nearly fills your whole bar without many ingredients.
With meals, I think it's pretty OK. Just like breakfast, probably lunch (depending on how much you do) and dinner. I'd be really upset in reallife if I only had one meal a day, too. Personally, it doesn't bother me that much.