In general Advent does not have the same penitential fervor as Lent, but the Church did commemorate an ancient discipline of fasting in the days immediately before Christmas.
It was called "Advent Embertide" and corresponds to the tradition of "Ember Days." In the Western (Latin) Catholic Church there existed a liturgical custom that revolved around the changing of the four seasons and consisted of 3 days set apart for fasting and prayer.
In Latin these days were referred to as Jejunia quatuor tempora (the fast of the four seasons), while in English they became known as “Ember Days” (from a corruption of the Latin word tempora). These special days of fasting were established very early on in the Church and consisted of a Wednesday, Friday, and Saturday at the beginning of each season (Spring, Summer, Fall, and Winter).
According to the Catholic Encyclopedia, Ember Days were established “to thank God for the gifts of nature, to teach men to make use of them in moderation, and to assist the needy.”
During Advent these Ember Days focus our attention on the coming of the Messiah. ThoughtCo explains, "The readings for the December Ember Wednesday—Isaiah 2:2-5; Isaiah 7:10-15; Luke 1:26-38—prophesy the preaching of the Gospel to the Gentiles and call us to walk in the light of the Lord, and recount Isaiah's prophecy of the virgin who shall give birth to God among us, and then show us the fulfillment of that prophecy in the Annunciation."
Ember Friday moves on to the mystery of the Visitation and Ember Saturday recalls St. John the Baptist's exhortation to "prepare the way of the Lord."
There were also specific regulations for fasting on these three days and special Masses were said. For these reasons it was known as a "mini-Lent," highlighting the importance of prayer and fasting.
It gave Christians a last spiritual boost before Christmas that was aimed at turning their hearts to God. While no longer a part of the general calendar, many Christians today try to observe these final days of Advent as best they can, preparing their hearts for the arrival of Jesus on Christmas day.
