Non-Fasting Periods
For the Christian, all foods are clean. When no fast is prescribed, there are no forbidden foods.
Weekly Fast
Except during the periods the Church has declared fast-free (see below), the tradition of the Church is to keep a strict fast every Wednesday to recall the betrayal of Christ and every Friday in remembrance of Christ’s passion and death. The following foods are avoided on those days:
Meat, including poultry, and any meat products such as lard and meat broth.
Fish (meaning fish with backbones; shellfish are permitted).
Eggs and dairy products (milk, butter, cheese, etc).
Olive oil. A literal interpretation of the rule forbids only olive oil. Especially where olive oil is not a major part of the diet, the rule is sometimes taken to include all vegetable oils, as well as oil products such as margarine.
Wine and other alcoholic drink. In the Slavic tradition, beer is often permitted on fast days.
How Much?
Those raised in the faith can be tempted by spiritual sloth, a complacency which is especially addressed through the Church’s fasting and feasting cycles. Sadly, it is easy to keep the letter of the fasting rule and still practice gluttony. When fasting, we should eat simply and modestly. “Fasting is the soul of prayer, mercy is the lifeblood of fasting. So if you pray, fast; if you fast, show mercy; if you want your petition to be heard, hear the petition of others. If you do not close your ear to others, you open God’s ear to yourself.” -Saint Peter Chrysologus
Those new to the faith or to the eastern fasts are at risk of pride and legalism and they in particular should only begin fasting under the guidance of a priest or confessor. They should not attempt to undertake fasting, especially the full traditional fast, on their own. “Obedience is rightly placed before all other sacrifices, for in offering a victim as sacrifice, one offers a life that is not one’s own; but when one obeys one is immolating one’s own will.” -St. Gregory the Great
The Church has always exempted small children, the sick, the very old, and pregnant and nursing mothers from strict fasting. While people in these groups should not seriously restrict the amount that they eat, no harm will come from doing without some foods on two days out of the week — simply eat enough of the permitted foods. Exceptions to the fast based on medical necessity (as with diabetes) are always allowed.
Communion Fast
So that the Body and Blood of our Lord may be the first thing to pass our lips on the day of communion, we abstain from all food and drink from the time that we retire (or midnight, whichever comes first) the night before. Married couples abstain from the marital embrace the night before communion.
When communion is in the evening, as with Presanctified Liturgies during Lent, this fast should if possible be extended throughout the day until after communion. For those who cannot keep this discipline, a total fast beginning at noon is sometimes prescribed.
Lenten Fast
Great Lent is the longest and strictest fasting season of the year.
Week before Lent (Cheesefare Week): Meat and other animal products are prohibited, but eggs and dairy products are permitted, even on Wednesday and Friday.
First Week of Lent: Only two full meals are eaten during the first five days, on Wednesday and Friday after the Presanctified Liturgy. Nothing is eaten from Monday morning until Wednesday evening, the longest time without food in the Church year. (Few laymen keep these rules in their fullness.) For the Wednesday and Friday meals, as for all weekdays in Lent, meat and animal products, fish, dairy products, wine and oil are avoided. On Saturday of the first week, the usual rule for Lenten Saturdays begins (see below).
Weekdays in the Second through Sixth Weeks: The strict fasting rule is kept every day: avoidance of meat, meat products, fish, eggs, dairy, wine and oil.
Saturdays and Sundays in the Second through Sixth Weeks: Wine and oil are permitted; otherwise the strict fasting rule is kept.
Holy Week: The Thursday evening meal is ideally the last meal taken until Pascha. At this meal, wine and oil are permitted. The Fast of Great and Holy Friday is the strictest fast day of the year: even those who have not kept a strict Lenten fast are strongly urged not to eat on this day. After St. Basil’s Liturgy on Holy Saturday, a little wine and fruit may be taken for sustenance. The fast is sometimes broken on Saturday night after Resurrection Matins, or, at the latest, after the Divine Liturgy on Pascha.
Wine and oil are permitted on several feast days if they fall on a weekday during Lent. Consult your parish calendar. On Annunciation and Palm Sunday, fish is also permitted.

Apostles’ Fast
This fast begins 8 days after Pentecost and culminates on the Feast of the Apostles Peter and Paul (June 28). Depending on when Pascha falls, the fast lasts anywhere from 1-6 weeks. The rule for this variable-length fast is more lenient than for Great Lent.
Monday, Wednesday, Friday: Strict fast.
Tuesday, Thursday: Oil and wine permitted.
Saturday, Sunday: Fish, oil and wine permitted.
This is the rule kept by many monasteries during non-fasting seasons.

Dormition Fast
This fast comprises two weeks of preparation to celebrate the Dormition of the Theotokos on August 15. Fasting during the two-week Dormition fast is like that during most of Great Lent:
Monday-Friday: Strict fast.
Saturday and Sunday: Wine and oil permitted.

Nativity Fast
This is the 40 days of fasting to prepare for the Nativity Feast (Christmas) and the Great Feast of Theophany. During the early part of the fast, the rule is identical to that of the Apostles’ Fast. During the latter part of the fast, fish is no longer eaten on Saturdays or Sundays. In different traditions, this heightening of the fast may be for either the last week or the last two weeks.
The Holy Supper meal on the eve of the Nativity is a traditional fasting meal in the Ukrainian Church.

Other Fasts
The Eve of Theophany, the Exaltation of the Cross and the Beheading of John the Baptist are fast days, with wine and oil allowed.
Marital Fast
Married couples are expected to abstain from the marital embrace throughout the Church’s four fasting seasons as well as on the weekly Wednesday and Friday fasts and the Communion fast.

This aspect of the fasting rule is probably even more widely ignored, and more difficult for many, than those relating to food. In recognition of this, some sources advocate a more modest, minimal rule: couples should abstain from the marital embrace before receiving Holy Communion and throughout Holy Week.

Fast-Free Periods
Complementing the four fasting seasons of the Church are four weeks completely free of fasting:
Nativity to Eve of Theophany.
Week following the Sunday of the Publican and Pharisee.
Bright Week — the week after Pascha.
Trinity Week — the week after Pentecost, ending with All Saints Sunday.

Obviously, many do not keep the traditional rule. The rules given here are of course only one part, the most external part, of a true fast, which will include increased prayer and other spiritual disciplines, and may include resolutions to set aside other aspects of our day-to-day life (such as caffeine or television), or to take up practices such as visiting the sick. Do not substitute the notion of “deciding what to give up for Lent” for the rule that the Church has given us. First, keep the Church’s fasting rule as well as you are able, then decide on additional disciplines, in consultation with your priest.
The purpose of this material is to be descriptive in respective to the issues it addresses. While the material is accurate, it is not definitive. Neither is it legalistic in its intent not does it pretend to be normative. It is shared in response to the queries posed to the author in regards to the church’s ancient traditions. All people should seek out and defer in humility to the guidance of their priest, bishop, and Church.
Adapted with appreciation from text originally posted by the famous parishioners of the soon-to-become-famous (at least on the Internet) St. Elias the Prophet parish on their page on fasting and by Reader John Brady’s page on the same topic on his AbbaMoses website.