Is abstaining from meat only required during Lent?

Yes. And no.

I have talked with people who rightly knew that the obligation to abstain from meat on the Fridays of the year except during the season of Lent and on Good Friday is no longer in effect (at least in the US as I'm not sure about other countries). However, many where surprised to learn that we are still under an obligation to practice some form of self-denial and penance on Fridays during the rest of the year.

The Code of Canon Law states:

CHAPTER II.

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.

Canon Law gives the bishops conference's the authority to substitute other forms of penance for abstaining from meat on Fridays. The United States Conference of Catholic Bishops addressed this in 1966 in its Pastoral Statement on Penance and Abstinence.

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. Our expectation is based on the following considerations: a. We shall thus freely and out of love for Christ Crucified show our solidarity with the generations of believers to whom this practice frequently became, especially in times of persecution and of great poverty, no mean evidence of fidelity to Christ and His Church. b. We shall thus also remind ourselves that as Christians, although immersed in the world and sharing its life, we must preserve a saving and necessary difference from the spirit of the world. Our deliberate, personal abstinence from meat, more especially because no longer required by law, will be an outward sign of inward spiritual values that we cherish.

25. Every Catholic Christian understands that the fast and abstinence regulations admit of change, unlike the commandments and precepts of that unchanging divine moral law which the Church must today and always defend as immutable. This said, we emphasize that our people are henceforth free from the obligation traditionally binding under pain of sin in what pertains to Friday abstinence, except as noted above for Lent. We stress this so that "no" scrupulosity will enter into examinations of conscience, confessions, or personal decisions on this point.

26. Perhaps we should warn those who decide to keep the Friday abstinence for reasons of personal piety and special love that they must not pass judgment on those who elect to substitute other penitential observances. Friday, please God, will acquire among us other forms of penitential witness which may become as much a part of the devout way of life in the future as Friday abstinence from meat. In this connection we have foremost in mind the modern need for self-discipline in the use of stimulants and for a renewed emphasis on the virtue of temperance, especially in the use of alcoholic beverages.

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. 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.

I mention this because I am guilty of not observing the Friday obligation, even after my ignorance on the matter was relieved. Personally, I've decided to start making the habit of observing the traditional abstinance from meat on Fridays. At any rate we are all still obligated to make some act of penance on all Fridays of the year.