This open access book explores how medical advice on diet, exercise, and body weight evolved in Britain between 1670 and 1830. Focusing on the growing use of measurement and quantification, it shows how ideas of a ‘healthy’ body were defined and debated in medical literature. Bringing together three topics rarely examined in combination, the study offers a fresh perspective on eighteenth-century health practices. Drawing primarily on printed health guides, alongside letters and diaries, it argues that the period from 1680 to 1780 marked a formative moment in the development of modern health advice.