What is the Byzantine Catholic Eucharist Fast?

Fasting and Vigils in the Life of the Church

The liturgical books of the Byzantine Rite say very little about fasting; in fact, they are more likely to say when food is to be eaten rather than when it is not. But the self-discipline that comes from fasting, and the watchfulness that comes from keeping vigil, are important Christian virtues, and so both fasting and vigils are an important aspect of Byzantine liturgy.

The Eucharistic Fast

In the early Church, the Eucharist was sometimes celebrated in the context of a meal, and there was little sense that Holy Communion should be separated entirely from ordinary food. But over time, a sense of the enormity of receiving the Body and Blood of Christ (and the fear that some might receive it unworthily to their own harm) led to a sense that one should pray, purify oneself, and fast before Holy Communion. To this day, in some Orthodox churches, confession, absolution, and one or more days of fasting are required for each reception of the Body and Blood of Christ.

The Byzantine Catholic liturgikon for the Divine Liturgy opens with the following:

The priest who intends to celebrate the divine mystery should be reconciled, first of all, with everyone and have no animosity toward anyone. To the best of his ability, he must keep his mind free from evil thoughts. He must abstain from food and drink in accordance with ecclesiastical legislation until his liturgical function...

Here the spiritual requirements are followed by bodily ones: the priest is expected to fast from food and water, generally from the night before. The particular law for our church states that those receiving Holy Communion must fast from food and drink for at least one hour (water and medication are permitted), but the faithful are encouraged to fast more strictly, in accordance with tradition.

Why fast before Holy Communion? In order to show that we recognize the great value of the Gifts we will receive. This is not a punishment or a penance (both of which are excluded on Sundays), but a positive recognition of the great mystery and importance of the Eucharist.

source: https://mci.archpitt.org/liturgy/Fasting.html

They are an important, though sometimes understated, aspect of Byzantine liturgical practice, contributing to spiritual growth and preparation for encountering the sacred.

Initially, the Eucharist was often celebrated within the context of a meal, with less emphasis on separation from ordinary food. However, over time, a profound appreciation for the sacredness of receiving the Body and Blood of Christ emerged, coupled with a concern about unworthy reception.

The priest should be reconciled with everyone, free from animosity, and strive to keep his mind clear of evil thoughts. Physically, he is expected to abstain from food and drink, generally from the night before the liturgy, in accordance with ecclesiastical legislation.

The specific law in the Byzantine Catholic Church requires those receiving Holy Communion to abstain from food and drink (though water and medication are permitted) for at least one hour beforehand. However, the faithful are encouraged to follow the broader tradition and fast more strictly if they are able.