“Ash Wednesday and Good Friday are obligatory days of fasting and abstinence for Catholics. In addition, Fridays during Lent are obligatory days of abstinence.
For members of the Latin Catholic Church, the norms on fasting are obligatory from age 18 until age 59. When fasting, a person is permitted to eat one full meal, as well as two smaller meals that together are not equal to a full meal. The norms concerning abstinence from meat are binding upon members of the Latin Catholic Church from age 14 onwards.”
That’s actually all you need to know, and you can stop here if you desire. But, for those who, like me, are detail nitnoids, there’s much more that follows below:
The full text of the current law, as laid down by the 1983 Code of Canon Law, Can.1249-1253, is this:
Days of Penance
Can. 1249 The divine law binds all the Christian faithful to do penance each in his or her own way. In order for all to be united among themselves by some common observance of penance, however, penitential days are prescribed on which the Christian faithful devote themselves in a special way to prayer, perform works of piety and charity, and deny themselves by fulfilling their own obligations more faithfully and especially by observing fast and abstinence, according to the norm of the following canons.
Can. 1250 The penitential days and times in the universal Church are every Friday of the whole year and the season of Lent.
Can. 1251 Abstinence from meat, or from some other food as determined by the Episcopal Conference, is to be observed on all Fridays, unless a solemnity should fall on a Friday. Abstinence and fasting are to be observed on Ash Wednesday and Good Friday.
Can. 1252 The law of abstinence binds those who have completed their fourteenth year. The law of fasting binds those who have attained their majority, until the beginning of their sixtieth year. Pastors of souls and parents are to ensure that even those who by reason of their age are not bound by the law of fasting and abstinence, are taught the true meaning of penance.
Can. 1253 The conference of bishops can determine more precisely the observance of fast and abstinence as well as substitute other forms of penance, especially works of charity and exercises of piety, in whole or in part, for abstinence and fast.”
There is also, on the same USCCB page, a Pastoral Statement on Penance and Abstinence (dated 18 November 1966) which covers both Advent and Lent, and Fridays in general as a day of penance. I have clipped a couple of interesting tidbits:
“12. Wherefore, we ask, urgently and prayerfully, that we, as people of God, make of the entire Lenten Season a period of special penitential observance. Following the instructions of the Holy See, we declare that the obligation both to fast and to abstain from meat, an obligation observed under a more strict formality by our fathers in the faith (my emphasis on this thought provoking clause), still binds on Ash Wednesday and Good Friday. No Catholic Christian will lightly excuse himself from so hallowed an obligation on the Wednesday which solemnly opens the Lenten season and on that Friday called "Good" because on that day Christ suffered in the flesh and died for our sins.
13. In keeping with the letter and spirit of Pope Paul's Constitution Poenitemini, we preserved for our dioceses the tradition of abstinence from meat on each of the Fridays of Lent, confident that no Catholic Christian will lightly hold himself excused from this penitential practice.
14. For all other weekdays of Lent, we strongly recommend participation in daily Mass and a self-imposed observance of fasting (my emphasis).”
Both the Priestly Fraternity of St Peter (FSSP) and the Society of St. Pius X (SSPX) require the current discipline, along with the Universal Church, although both organizations recommend and strongly encourage the older, more rigorous disciplines. The current and older disciplines can be found in many places side by side. Here is an example from The Parish of St. Peter, Tulsa, OK:
“Rules for Fasting and Abstinence
FASTING The obligation to fast applies to all Catholics who meet the age requirements (see below) on the required days unless they have a medical condition which prevents them from doing so, are pregnant or nursing, or their work would be impaired. On days of fasting:
•One full meal is allowed (with meat, unless it is also a day of abstinence).
•Two smaller meals without meat, which together do not equal the main meal, are permitted to maintain strength.
•No food or snacks are permitted between meals.
•Liquids are permitted, but care should be taken not to violate the spirit of the fast.
ABSTINENCE On days of full abstinence one is not permitted to eat the flesh of warm-blooded animals or soups or gravies made with the flesh of such animals. On days of partial abstinence (traditional rules only) one meal containing meat is permitted.
Traditional (1962) Discipline
Fasting obligations applied to those between the ages of 21 and 59, inclusive, except as noted above. Abstinence obligations applied to those age 7 and older.
Fasting was required on Ash Wednesday, the three following days, all days of Lent, Ember days, and vigils.
Full abstinence was required on Ash Wednesday, all Fridays during the year, and the vigil of Christmas. Partial abstinence was required on all days of Lent, Wednesdays and Saturdays of the Ember weeks, and all vigils (except Christmas).
The requirements for fasting and abstinence did not apply on Holy Days of Obligation (including Sundays).
Fasting obligations apply to those between the ages of 18 and 59, inclusive, except as noted above. Abstinence obligations apply to those age 14 and older. Canon law explicitly requires that pastors and parents ensure that minors not under these obligations are taught the true meaning of penance.
Fasting and abstinence are required on Ash Wednesday and Good Friday. Fasting on Holy Saturday is recommended, but not required.
Abstinence is required on all Fridays of Lent unless they are solemnities. Fridays outside of Lent are penitential days: abstinence is recommended, but in the United States other forms of penance may be performed.
The current laws of fasting and abstinence bind under the pain of severe sin.”
Finally, since we’re on the topic, here’s what the Pastoral Letter mentioned above says about Fridays in general:
“23. Friday should be in each week something of what Lent is in the entire year. For this reason we urge all to prepare for that weekly Easter that comes with each Sunday by freely making of every Friday a day of self-denial and mortification in prayerful remembrance of the passion of Jesus Christ.
24. Among the works of voluntary self-denial and personal penance which we especially commend to our people for the future observance of Friday, even though we hereby terminate the traditional law of abstinence binding under pain of sin, as the sole prescribed means of observing Friday, we give first place to abstinence from flesh meat. We do so in the hope that the Catholic community will ordinarily continue to abstain from meat by free choice as formerly we did in obedience to Church law…
27. It would bring great glory to God and good to souls if Fridays found our people doing volunteer work in hospitals, visiting the sick, serving the needs of the aged and the lonely, instructing the young in the Faith, participating as Christians in community affairs, and meeting our obligations to our families, our friends, our neighbors, and our community, including our parishes, with a special zeal born of the desire to add the merit of penance to the other virtues exercised in good works born of living faith.
28. In summary, let it not be said that by this action, implementing the spirit of renewal coming out of the Council, we have abolished Friday, repudiated the holy traditions of our fathers, or diminished the insistence of the Church on the fact of sin and the need for penance. (my emphasis) Rather, let it be proved by the spirit in which we enter upon prayer and penance, not excluding fast and abstinence freely chosen, that these present decisions and recommendations of this conference of bishops will herald a new birth of loving faith and more profound penitential conversion, by both of which we become one with Christ, mature sons of God, and servants of God's people. N.B. The effective date of these regulations is the first Sunday of Advent, November 27, 1966.”
There it is.