Galen compiled an extensive record of Greek medical knowledge in the second century A.D. "Galenic answers to virtually all medical questions dominated theory and practice into the 1600s, but while most features of Galenism were cast aside during that century, the code of hygiene retained its hold. It was ordered around the individual's careful regulation of those factors of existence over which he had control: air, food and drink, sleep and watch, motion and rest, evacuation and repletion, and passions of the mind. Attention to these…had been urged by medical writers throughout the Middle Ages and Renaissance, but the matter seemed to assume new importance during the mid-1700s."
Whorton, J. (1982) Crusaders for fitness: the history of American health reformers. Princeton University Press. USA
Harper suggests that one of the reasons why the rules for healthy living influenced many of the health movement s of the eighteenth and nineteenth centuries were that "they were compatible with the theology of the times in providing a moralistic solution to the sins of gluttony, sloth and intemperance to which illness was attributed. Present-day dietary guidelines are a modern version of some of these rules. The objective remains the same – guidance for healthy living with moralistic overtones – but is now bolstered by scientific observations."
Harper, A.E. (2000) Recommended Dietary Allowances and Dietary Guidance. Cambridge World History of Food. Cambridge University Press.