Natalia Mehlman Petrzela traces how fitness became a multi-billion dollar industry and marker of class identity in America, creating the paradox of a fitness-obsessed nation where most people remain sedentary. Petrzela, a historian at the New School, examines how activities once associated with manual labor became markers of affluence, how the fitness industry emerged from counterculture roots to become big business, and how access to exercise became stratified by race and class. The book covers the history of jogging, aerobics, CrossFit, and boutique fitness studios, showing how each movement promised democratic health while producing new forms of exclusion. Petrzela interviews fitness entrepreneurs, examines industry publications, and analyzes how exercise has been marketed to different demographics. She traces how fitness became moral: how the fit body came to signify discipline and success while the unfit body marked failure, regardless of the structural factors that determine who has time, money, and safe spaces to exercise. The book connects fitness culture to broader American themes of self-improvement, meritocracy, and the privatization of public goods. Petrzela writes engagingly about material that could be either celebratory or dismissive, instead producing critical history that takes its subject seriously while revealing its contradictions.