Judi Beth Liebowitz is thirteen and weighs 129 pounds making her think she is the fattest girl in her school. Judi believes if only she had those creamy thighs and perfect cheeckbones she could have her secret crush, Richard Weiss. When Judy stumbles into Nancy Pratt's "beauty secret" she realizes just how dangerous looking thin can be.

Judi Liebowitz has two goals:to be the thinnest girl in her school and to be the future Mrs. Weiss. After Judi's teacher assigns everyone a journal which they are to keep their most intimate thoughts and dreams in, Judi explains how she plans to become thin and walks us through it every step of the way. Judi's first idea is to stop eating but when her mom finds out she has been starving herself she must find a new way to lose weight. Monica, her best friend, begins to date Judi's secret crush Richard Weiss and they are no longer talking. Judi becomes friends with Nancy Pratt, the thinnest girl in the school, who gives her a few beauty tips. Judi begins her binge and purge lifestyle thinking nothing bad would happen but when Nancy has been sent to the hospital things change and for her it may be too late to turn back. Nancy is being forced to eat food in the hospital but gets Judi to buy her laxatives to keep the wieght off. Even though Judi doesn't feel it is right she is afraid that Nancy will tell the whole school about her bulimia problem since everyone thinks Nancy is in the hospital for a stomach ulcer. She then realizes that Nancy is not her true friend and apologizes to Monica for how silly she has been acting but unforunately her problem is no laughing matter. Monica urges her to get help and confess to her mother.

Judi confesses to her mom and gets therapy on her binge and purge disease. As for Nancy, she was not so lucky and is sent to a bulimia camp where she will spend several years.