Those first meals following a period of fasting are excellent for the purpose of learning what foods are really undesirable or harmful to one's own body. At such a time its instinct is much clearer and unperverted, while the ability to respond to its advice is much greater. Bad habits of feeding or living, such as gluttony or excessive smoking, can then be broken more easily. But it is necessary to concentrate all one's attention very carefully to note physical responses to each mouthful.
-- Perspectives > Chapter 5: The Body > # 10