The name of a book I read about thirty years ago

[luriabus]

Can someone help me locate a book I read a loong time ago. It's about anorexia nervosa. It was a novel. It centered around a very beautiful girl who got the idea that she was fat. She started dieting and exercising obsessively. What I remember a lot is that her boyfriend said she had a potbelly wchich is why she started her frenzy. It was one of those young adult books but I can�t remember the title or the author.