In 1727, the English physician Thomas Short wrote: “I believe no Age did ever afford more instances of Corpulency than our own.” Even in the 18th century, fatness was addressed as an issue of special contemporary concern. This thesis probes concepts and perceptions of fatness in Western European Medicine c. 1700–1900. It has been written with particular attention to whether and how fatness has been regarded as a disease during that period in history. One purpose of the thesis is to investigate the immediate period before fatness allegedly became problematized. Another purpose has been to grasp both its presence in medicine and the – sometimes strange – absence in both centuries.