Augustus had never gone without food for a long period of time. When his best memories and happiest feelings were being sucked away by the dementors, he had no appetite. His meager rations sufficed. Once he was away from their influence, he ate more than any two men combined. It was only the benefit of having excellent genes that kept him from blowing up to an enormous size. If he had to worry about where the next meal was coming from and when it was going to arrive, he might go mad. Much like Ron during that horrible horcrux hunt, he would struggle with hunger.