User blog comment:LuffyPirateKing/Luffy and his belly/@comment-1595565-20121021173205/@comment-1595565-20121021203344

Because, if it wasn't due to his body, then why bother mentioning it at all? The body thing was a quick explanation for how he is able to sustain it. Whereas the way he was able to absorb it seems to connect more to his fruit. There are two things at work. Look at the big picture.