I found an interesting blogpost in Boing Boing (Boing Boing: What does Atkins *mean*?) that referenced an article titled The Great Neurotic Art about food and dietary control in history. The article is written by the science historian Steven Shapin.
At the same time, it was widely, if not universally, acknowledged between traditional physicians and their patients that appetite was a pretty good guide to the healthfulness of foods. If you liked it, it probably liked you: the Renaissance and early modern maxim was ‘you should eat what you are.’ If you had a hot and moist complexion, then the foods that suited you best also tended to the hot and moist. (This was one reason cannibalism proved so interesting to dietary writers, since, in theory, no meat better suited to the human constitution could exist. Pork was a distant second.) That is, there were cosmological grounds for concluding that a little of what you fancy does you good.