http://www.greekmedicine.net/hygiene/Fasting_and_Purification.html
Here's something else to consider. Hippocrates, the Father of Modern Medicine believed in fasting.
Basically, there are two kinds of purposes or objectives for fasting. Men fast for either spiritual or physical reasons, and both are equally valid.
Spiritually, fasting helps us transcend our addiction and attachment to food, and to realize that man doesn't live by bread alone. The mind gets clearer, and spiritual awareness deepens. Freed from having to satisfy physical hunger, one can then turn one's attention to feeding the mind and spirit. Spiritual masters like Pythagoras wouldn't admit any disciple into their higher teachings unless they had first purified themselves through fasting.
Physically, fasting enables the organism to detoxify and clean house. Because the vast majority of diseases are caused by
autointoxication, fasting has wide-ranging therapeutic benefits. It also gives the digestive organs a much needed rest.
For all fevers and diseases in the acute crisis stage, Hippocrates prescribed either a strict fast with nothing but water or medicinal teas, or a very slender liquid diet. Fasting is also recommended for colds and flu, arthritis and rheumatism, digestive complaints, and all humoral and metabolic disorders.
Scientific experiments conducted on laboratory mice have shown that severe restriction of caloric intake greatly extends their lifespan. Since this is basically what fasting is, fasting holds great promise for life extension.