Background: The link between longevity and diet is of great interest to biological and gerontological research. The fact that relevant knowledge has generally been available for many centuries is often not remarked upon. Objective: This article examines three aspects of early modern Western medicine which thematize the following links between the elderly, longevity and caloric intake: (1) the question of a diet specifically tailored to old age as background to certain theories of aging; (2) the transfer of these dietetic concepts to younger patients in order to improve health and extend life, and (3) the promotion of dieting in order to avoid the consequences of plethora and to retard the aging process. Methods: A number of Latin texts from premodern medical and health literature will be examined and their contents will be analyzed for material relating to diet for the elderly and longevity in their historic contexts. Results: We will clearly indicate fundamental parallels as well as differences between historic and modern scientific thought. We will thereby show that although a modern understanding of hormones and molecular genetics was obviously lacking, basic knowledge of the influence of nutrition on old age was prevalent. In contrast, the early modern lay concept of longevity through calorie reduction was based on coincidental observation. Conclusion: These premodern, but nonetheless rational ideas must be integrated into the socio-cultural setting and the question must be raised as to the link between contemporary research aims and social reality.