Why?

Why is he really hungry? I mean, do we even know what he is hungry for? Is he searching for actual food or affections or material goods or else? In the book, he is obviously hungry for physical food because he is not well fed. However, it does not look like the physical hunger is the only thing that he desires for. It seems like his hunger is closely related to the absence of his dad. He feels hungry whenever he thinks about his dad being gone. Part of it is probably because of the financial situation at his house after his dad left. Also, he probably feels like his dad has abandoned him. So there is this sense of emptiness and loneliness that is helpless. Nothing can fulfill his desire for “food”.