The Eucharistic Fast
In brief
The Eucharistic fast is the total abstinence from food and drink that Orthodox Christians keep before receiving Holy Communion — traditionally from the previous midnight, or as one's priest directs. It is a different kind of fast from the seasonal rules: those govern what you eat, while this one governs whether you eat at all before the Chalice, so that the Body and Blood of Christ are the first thing to pass your lips that day. It is one strand of a fuller preparation that also includes prayer, confession, and reconciliation.
A different kind of fast
The seasonal and weekly fasts — Great Lent, the Wednesdays and Fridays, the Nativity and other fasts — are about the kind of food: meat, dairy, fish, wine, and oil are set aside on the appointed days. The Eucharistic fast is not about the kind of food at all. It is a total fast — nothing to eat or drink — kept for a set time before approaching the Chalice. Its logic is simple reverence: that the very first thing to enter the mouth on a Communion morning should be the Lord Himself, received on an empty stomach as the day's first and best food.
This is why an Orthodox Christian will typically come to the Liturgy having eaten and drunk nothing since waking — not even water, coffee, or breakfast — precisely so that they arrive hungry for the one food that matters. The fast is small in itself, a matter of a few morning hours, but it trains the body to say with its emptiness what the soul confesses: that here is the Bread of Life.
From midnight — or as directed
The custom of receiving Communion only while fasting is ancient and nearly universal. An early canon of the Council of Carthage directed that the Holy Gifts be offered only by those who are fasting, and St. Augustine already treated the practice as observed throughout the whole world. In its traditional form the fast runs from the previous midnight; in stricter reckonings, from the end of the evening meal the night before. Because Orthodox worship counts the day from sunset, the fast naturally embraces the whole morning up to Communion.
How strictly this is applied varies, and here the Church's principle of economia fully applies. The sick, the elderly, small children, expectant mothers, diabetics, and those who must take medication with food or water are not bound as a healthy adult is; a long all-night vigil may shift the reckoning; and jurisdictions differ in their pastoral counsel. The rule is not a hurdle to clear on your own but a discipline to keep as your health and circumstances honestly allow — which is exactly the kind of question to bring to your priest rather than settle in private.
One strand of preparing
The Eucharistic fast is never meant to stand alone, as though an empty stomach were the whole of readiness. It belongs to a larger preparation for Holy Communion: the pre-Communion prayers and canons, recent confession as one's spiritual father advises, and reconciliation with anyone one has wronged. St. Paul's warning that a person should "examine himself" before eating and drinking (1 Corinthians 11:28) points past the body to the heart.
Held together, these make the fast what it is meant to be — not a ticket to be punched, but the body's share in a whole person turning toward the Chalice. The hunger of the morning is answered at the words "With the fear of God, and faith, and love, draw near," when the fast ends in the only way it was ever meant to end: in Communion.