What other customary Catholic fasting periods are there aside from Lent?
There are several historical fasts that have now disappeared, just like the dodo bird. But every once in awhile they seems to make somewhat modified appearances here and there.
St. Francis of Assisi was very fond of fasting and some of the fasting that was somewhat popular in his day have now almost totally disappeared.
The Fasts of Saint Francis
The Fast in Honor of Mary
“He embraced the Mother of Our Lord Jesus with indescribable love because, as he said, it was she who made the Lord of majesty our brother, and through her we found mercy. After Christ, he put all his trust in her and took her as his patroness for himself and his friars. In her honor he fasted every year from the feast of Saints Peter and Paul until the Assumption.”
The Fast of Christmas
All the friars without exception must fast from the feast of All Saints until Christmas...” in preparation for Christmas and so he did.
The “Benedictus” Fast
“In his extraordinary devotion to Christ, he fasted every year for forty days, beginning at the Epiphany, the time when Christ himself lived in the desert. Then he would go to some lonely place and remain there shut up in his cell, taking as little food and drink as possible, as he spent all his time praying and praising God.”
The Fast in Honor of St. Michael and the Angels
“He had an unshakable love for the Angels who burn with a marvelous fire, so that they are taken out of themselves to God and long to inflame the souls of the elect. Each year he fasted and prayed in their honour for forty days from the feast of the Assumption.”
This fast lasted from June 29th until August 15th each year.
The Fast in Honor of Peter and Paul
“He also kept most devoutly a fast of forty days in honor of St. Michael between the feast of the Assumption and his feast.” Hence, this fast, for the angels, whom he loved dearly, began on the Assumption and ended forty days later, i.e. the feast of St. Michael the Archangel, September 29th.
“...he embraced all of the Apostles with the greatest affection, and especially Saints Peter and Paul because of their passionate love of Christ. In his reverence and love for them, he used to keep a special forty-day fast in their honour.” This fast ended on the feasts of SS Peter and Paul, June 29th, at which time the fast in honor of Our Lady was begun.
The Lenten Fast
“All the friars are to keep the Lenten fast before Easter...” and so he did too.
Of these various fasts which St. Francis and his friars observed, he established two, the Christmas fast (from the day after the feast of St. Martin until Christmas), and the Lenten fast, as appropriate for laity under the First Rule of the Third Order.
St. Benedict of Nursia encouraged his monks to fast often and this can be seen in the Rule of St. Benedict:
Chapter 41:At What Hours the Brethren ought to have their Meals
From holy Easter until Pentecost let the brethren dine at the sixth hour and sup about sunset; but on the Wednesdays and Fridays during the whole summer, from Pentecost, unless the monks have field work, or the excessive heat of the summer tries them, let them fast until the ninth hour; and on the other days let them dine at the sixth hour. And they should continue to dine thus at the sixth hour if they have been doing field work or if the heat of the summer be oppressive; and let this be within the discretion of the abbot; and similarly let him modify and arrange everything in such wise that both souls be saved and also that what the brethren do they may do without just cause for murmuring. From the fourteenth of September until the beginning of Lent let them always dine at the ninth hour; but in Lent until Easter let them dine at an evening hour; but let that evening hour be so ordered that when dining they may not require the light of a lamp, but may be quite finished while daylight still lingers. And indeed on all occasions let the hour, whether of supper or dinner, be so suitably arranged that everything be done by daylight.
If there is an element in the Benedictine Rule which has ceased to be practiced in the twentieth century, it is indeed this one. There is an obvious contrast and a complete contradiction between the schedule of meals as set by Saint Benedict and the customs prevailing in the Benedictine monasteries of our days.
Nevertheless, there are still some monasteries (Congregation on Solesmes) that still fast on every Friday from the Feast of the Holy Cross (September 14) until the end of Lent.
Some fast on Wednesdays in memory of Judas’ betrayal.
Some fast on Fridays in memory of the crucifixion.
Historically a Black Fast was kept on the days preceding one's ordination to the diaconate and priesthood as well as the sacred ministers involved.
Some fast on Saturdays in honour of Mary. For example, St Mary of Jesus Crucified fasted on Saturday’s in honour of the Virgin Mary.
As you can guess, this is a subject matter I enjoy immensely. I like making it come alive by going on all Medieval on myself. I love an historical Medieval Ember Day Tart for those Ember Days!
By the way, according to the Didache, the Early Church fasted on Wednesdays and Fridays.
Chapter 8 suggests that fasts are not to be on the second day and on the fifth day "with the hypocrites", but on the fourth day and on the preparation day. Fasting Wednesday and Friday plus worshiping on the Lord's day constituted the Christian week. Nor must Christians pray with their Judaic brethren; instead they shall say the Lord's Prayer three times a day. The text of the prayer is not identical to the version in the Gospel of Matthew, and it is given with the doxology "for Yours is the power and the glory forever." This doxology derives from 1 Chronicles 29:11–13; Bruce M. Metzger held that the early church added it to the Lord's Prayer, creating the current Matthew reading.
Many exorcists fast just prior and during exorcisms. Let remember the word of Jesus to his disciples: But this kind is not cast out but by prayer and fasting (Matthew 17:20-22). Several of the Fathers of the Church, including Irenaeus, Tertullian, Cyprian, and Athanasius provide us with insights into the exorcistic practices of their day through their extant writings. Through them we gain a glimpse into the unfolding developments in the structure and form of exorcism as a rite gradually took shape. In addition to the use of Jesus' name, other elements contributed to the shape of an early ritual such as the Sign of the Cross, exsufflation (breathing on the person's face), simple adjurations containing scripture, prayer, and fasting.
St. John Vianney fast fasted almost every day!