What is the main conflict in Staying Fat for Sarah Byrnes by Chris Crutcher?

Moby is a high school senior whose best friend, Sarah Byrnes, has been put in a hospital because she refuses to speak. Sarah Byrnes, a young woman disfigured by burns she received when she was three, has always been a friend to Moby even when his excess weight made him an outcast at school. Now Sarah Byrnes needs Moby to be her strength like she was his in junior high. Moby does not know who he can trust but finds himself turning to the most unlikely people to find a way to protect his best friend. Staying Fat for Sarah Byrnes is about being an outcast, about friendship, and about standing up for what is right, even when it means betraying the trust of the one who has always been there.