Those engaged in spiritual warfare regain their original state by practicing two commandments - obedience and fasting; for evil has infiltrated our human condition by means of their opposites.
Gregory of Sinai presents fasting as one of two foundational remedial commandments by which the practitioner reverses the primal fall, assigning it specifically to those in the middle way who have achieved a degree of self-mastery.
, The Philokalia, Volume 4, 1995thesis