Board Thread:Naruto Discussions/@comment-25374031-20140917212238/@comment-9782468-20140925033847

Jiraiya coudln't balance his energies properly, that's why he looked more like a toad.

Once Naruto could balance his energies perfectly, he stopped becoming like a toad. And he became even more powerful than Jiraiya in sage mode. Even if Naruto took in more energy, as long as he kept the energy in him balanced, he wouldn't look more toad-like.