A trick of light theme

My book is called a trick of light and the author is Lois metzger. It's about this kid who starts gaining weight & put of shape for the baseball team. because he starts getting problems with his family. He starts eating and gains a lot of weight to keep the mind out of it. He starts getting voices in his head & tells him to lose weight. He comes across a girl who has a eating disorder. She also helps him to lose weight. the theme of the book is that fat people can lose weight too. In page 25 his mom tells him how wide he was when he looked in the mirror. " the glass is wavy, look how wide you are."