Here are some thoughts on fasting taken from Alexander Schmemann’s book ‘Great Lent’:
It is important, therefore, to discern the uniquely Christian content of fasting. It is first of all revealed to us in the interdependence between two events which we find in the Bible: one at the beginning of the Old Testament and the other ar the beginning of the New Testament. The first event is the “breaking of the fast” by Adam in Paradise. He ate of the forbidden fruit. This is how man’s original sin is revealed to us. Christ, the New Adam–and this is the second event–begins by fasting. Adam was tempted and he succumbed to temptation; Christ was tempted and He overcame that temptation. The results of Adam’s failure are expulsion from Paradise and death. The fruits of Christ’s victory are the destruction of death and our return to Paradise. . . .
In the Orthodox teaching, sin is not only the transgression of a rule leading to punishment; it is always a mutilation of life given to us by God. It is for this reason that the story of the original sin is presented to us as an act of eating. For food is means of life; it is that which keeps us alive. But here lies the whole question: what does it mean to be alive and what does “life” mean? For us today this term has a primarily biological meaning: life is precisely that which entirely depends on food, and more generally, on the physical world. But for the Holy Scripture and for Christian Tradition, this life “by bread alone” is identified with death because it is mortal life, because death is a principle always at work in it. God, we are told, “created no death.” He is the Giver of Life. How then did life become mortal? Why is death and death alone the only absolute condition of that which exists? The Church answers: because man rejected life as it was offered and given to him by God and preferred a life depending not on God alone but on “bread alone.” Not only did he disobey God for which he was punished; he changed the very relationship between himself and the world. . . .
Christ is the New Adam. He comes to repair the damage inflicted on life by Adam, to restore man to true life, and thus He also begins with fasting. “When He had fasted forty days and forty nights, He became hungry” (Matt. 4:2). Hunger is that state in which we realize our dependence on something else–when we urgently and essentially need food–showing thus that we have no life in ourselves. It is that limit beyond which I either die from starvation or, having satisfied my body, have again the impression of being alive. It is, in other words, the time when we face the ultimate question: on what does my life depend? . . .
What then is fasting for us Christians? It is our entrance and participation in that experience of Christ Himself by which He liberates us from the total dependence on food, matter, and the world. By no means is our liberation a full one. Living still in the fallen world, in the world of the Old Adam, being part of it, we still depend on food. But just as our death–through which we still must pass–has become by virtue of Christ’s Death a passage into life, the food we eat and the life it sustains can be life in God and for God. . . .
All this means that deeply understood, fasting is the only means by which man recovers his true spiritual nature. It not a theoretical but truly a practical challenge to the great Liar who managed to convince us that we depend on bread alone and built all human knowledge, science and existence on that lie. Fasting is a denunciation of that lie and also the proof that it is a lie. It is highly significant that it was while fasting that Christ met Satan and that He said later that Satan cannot be covercome “but by fasting and prayer.” Fasting is the real fight against the Devil because it is the challenge to that one all-embracing law which makes him the “Prince of this world.” . . .
Ultimately to fast means only one thing: to be hungry–to go to the limit of that human condition which depends entirely on food and, being hungry, to discover that this dependency is not the whole truth about man, that hunger itself is first of all a spiritual state and that it is in its last reality hunger for God. In the early Church, fasting alway meant total abstinence, a state of hunger, pushing the body to the extreme. It is here, however, that we discover also that fasting as a physical effort is totally meaningless without its spiritual counterpart: “. . . by fasting and prayer.” This means that without the corresponding spiritual effort, without feeding ourselves with Divine Reality, without discovering our total dependence on God and God alone, physical fasting would indeed be suicide. If Christ Himself was tempted while fasting, we have not a single chance of avoiding that temptation. Physical fasting, essential as it is, is not only meaningliness, it is truly dangerous if it is disconnected from the spiritual effort–from prayer and concentration on God. . . .
It is for this reason that we need first of all a spiritual preparation for the effort of fasting. It consists in asking God for help and also in making our fast God-centered. We should fast for God’s sake.
[Great Lent, pp. 93, 94, 95, 96, 97.]