Although fasting is usually associated with Yom Kippur what the Old Testament actually says is that

you must "torment you soul" (a better translation might be: "to impoverish the soul"). In the New Testament a similar type of confusion occurs when Jesus tells the rich man "to give up all he has". Jesus was refering to the man's:  "wealth of knowledge" not his money. In the Old Testament: "food" is always a metaphor for: "knowledge". In the New Testament: "wealth" is always a metaphor for: "the teachings of men". So in the Old Testament the prohibition against eating milk and meat has nothing to do with diet. The "meat of the goat" represents: "a type of religious preaching" and: "milk" represents: "easy to understand spiritual teachings". From another perspective, the Buddha also interpreted the Hindu scriptures literally and fasted. He became so weak he almost died. Fortunately for him, he realized the error of his ways and this led to his enlightenment.