We were to fast from the beginning; our refusal was our downfall

St. Basil in an ancient and comprehensive sermon notes that "fasting is even older than the Law. If you wait a little, you will discover the truth of what I have said. Do not suppose that fasting originated with the Day of Atonement, appointed for Israel on the tenth day of the seventh month. (Lev. 23:27) No, go back through history and inquire into the ancient origins of fasting. It is not a recent invention; it is an heirloom handed down by our fathers. Everything distinguished by antiquity is venerable. Have respect for the antiquity of fasting. It is as old as humanity itself; it was prescribed in Paradise.

Adam and Eve expelled from the Garden, by Masaccio, ca. 1426-1428

"It was the first commandment that Adam received: 'Of the tree of the knowledge of good and evil ye shall not eat. (Gen. 2:17) Through the words 'ye shall not eat' the law of fasting and abstinence is laid down. If Eve had fasted from the tree, we would not now be in need of this fast. 'They that be whole need not a physician, but they that are sick.' (Matt. 9:12) We have been wounded through sin; we are healed through repentance, but repentance without fasting is fruitless. 'Cursed is the ground.... Thorns and thistles shall it bring forth for thee.' (Gen. 3:17-18) You were ordered to live in sorrow, not in luxury. Make amends to God through fasting. Yet even life in Paradise is an image of fasting, not only insofar as man, sharing the life of the Angels, attained to likeness with them through being contented with little, but also insofar as those things which human ingenuity subsequently invented had not yet been devised by those living in Paradise, be it the drinking of wine, the slaughter of animals, or whatever else befuddles the human mind."

Meum cum sim pulvis et cinis