The United States, we are told, is facing an obesity epidemic-a "battle of the bulge" of not just national, but global proportions-that requires drastic and immediate action. Experts in the media, medical science, and government alike are scrambling to find answers. What or who is responsible for this fat crisis, and what can we do to stop it?

Abigail Saguy argues that these fraught and frantic debates obscure a more important question: How has fatness come to be understood as a public health crisis at all? Why, she asks, has the view of "fat" as a problem-a symptom of immorality, a...