What is the main conflict in Fat Kid Rules the World by K. L. Going?

"Fat Kid Rules the World" by K. L. Going tells the story of a 17-year-old boy named Troy who is pushing 300 pounds. He has serious issues with his image and the book begins with Troy standing on the edge of the subway platform, contemplating suicide. He is distracted by an emaciated young man who is a popular, talented musician named Curt. They form a friendship that transforms each of them in unique ways.