Managing the Body explores the emergence of modern male and female bodies within the context of debates about racial fitness and active citizenship in Britain from the 1880s until 1939. It analyses the growing popularity of hygienic regimen or body management such as dietary restrictions, exercise, sunbathing, dress reform, and birth control to cultivate beauty, health, and fitness. These bodily disciplines were advocated by a loosely connected group of life reform and physical culture promoters, doctors, and public health campaigners against the background of rapid urbanization, the rise of modern lifestyles, a proliferation of visual images of beautiful bodies, and eugenicist fears about racial degeneration. The author shows that body management was an essential aspect of the campaign for national efficiency before 1914. The modern nation state needed physically efficient, disciplined citizens and the promotion of hygienic practices was an integral component of the Edwardian welfare reforms. Anxieties about physical deterioration persisted after the First World War, as demonstrated by the launch of new pressure groups that aimed to transform Britain from a C3 to an A1 nation. These military categories became a recurrent metaphor throughout the interwar years and the virtuous habits of the healthy and fit A1 citizen were juxtaposed with those of the C3 anti-citizen, whose undisciplined lifestyle was attributed to ignorance and lack of self-control. Practices such as vegetarianism, nudism, and men's dress reform were utopian and appealed only to a small minority, but sunbathing, hiking, and keep-fit classes became mainstream activities and they were promoted in the National Government's 'National Fitness Campaign' of the late 1930s.