Passage in question:
よっぽど おなかが すいて いたんだなあ。
As I understand, the translation is something along the lines of "You must have been very hungry." My problem lies within the bold text: how exactly each element of this passage is constructed? Dictionaries and rikaikun didn't quite help and I also don't know whether there are any kanji in the passage (although I doubt it) since I encountered it in a children's cartoon with kana-only subtitles.