Fasting is not very alive and well in the Christian world. Much of that world has long lost any living connection with the historical memory of Christian fasting. Without the guidance of Tradition, many modern Christians either do not fast, or constantly seek to re-invent the practice, sometimes with unintended consequences.
There are other segments of Christendom who have tiny remnants of the traditional Christian fast, but in the face of a modern world have reduced the tradition to relatively trivial acts of self-denial.
I read recently (though I cannot remember where) that the rejection of Hesychasm was the source of all heresy. In less technical terms we can say that knowing God in truth, participating in His life, union with Him through humility, prayer, love of enemy and repentance before all and for everything, is the purpose of the Christian life. Hesychasm (Greek Hesychia=Silence) is the name applied to the Orthodox tradition of ceaseless prayer and inner stillness.
But these are incorrectly understood if they are separated from knowledge of God and participation in His life, union with Him through humility, prayer, love of enemy and repentance before all and for everything.
And it is the same path of inner knowledge of God (with all its components) that is the proper context of fasting. If we fast but do not forgive our enemies – our fasting is of no use. If we fast and do not find it drawing us into humility – our fasting is of no use. If our fasting does not make us yet more keenly aware of the fact that we are sinful before all and responsible to all then it is of no benefit. If our fasting does not unite us with the life of God – which is meek and lowly – then it is again of no benefit.
Fasting is not dieting. Fasting is not about keeping a Christian version of kosher. Fasting is about hunger and humility (which is increased as we allow ourselves to become weak). Fasting is about allowing our heart to break.
I have seen greater good accomplished in souls through their failure in the fasting season than in the souls of those who “fasted well.” Publicans enter the kingdom of God before Pharisees pretty much every time.
Why do we fast? Perhaps the more germane question is “why do we eat?” Christ quoted Scripture to the evil one and said, “Man does not live by bread alone but by every word that proceeds from the mouth of God.” We eat as though our life depended on it and it does not. We fast because our life depends on the word of God.
I worked for a couple of years as a hospice chaplain. During that time, daily sitting at the side of the beds of dying patients – I learned a little about how we die. It is a medical fact that many people become “anorexic” before death – that is – they cease to want food. Many times family and even doctors become concerned and force food on a patient who will not survive. Interestingly, it was found that patients who became anorexic had less pain than those who, having become anorexic, were forced to take food. (None of this is about the psychological anorexia that afflicts many of our youth. That is a tragedy).
It is as though at death our bodies have a wisdom we have lacked for most of our lives. It knows that what it needs is not food – but something deeper. The soul seeks and hungers for the living God. The body and its pain become a distraction. And thus in God’s mercy the distraction is reduced.
Christianity as a religion – as a theoretical system of explanations regarding heaven and hell, reward and punishment - is simply Christianity that has been distorted from its true form. Either we know the living God or we have nothing. Either we eat His flesh and drink His blood or we have no life in us. The rejection of Hesychasm is the source of all heresy.
Why do we fast? We fast so that we may live like a dying man – and in dying we can be born to eternal life.