Those interested in the Science behind fasting might like to look at this story in Nature. Neural autophagy is enhanced in fasting. This study looked at another method to increase autophagy and showed memory in a fruit fly improved. This is in addition to other studies which show autophagy increased longevity.

For non biochemists autophagy is the cells process of digesting damaged or unwanted proteins and cellular machines (organelles).

http://www.nature.com/news/common-nutrient-keeps-flies-sharp-into-old-age-1.1...