According to the Canon Law of the Roman Catholic Church:
Canon 1252: All persons who have completed their fourteenth year are bound by the law of abstinence; all adults are bound by the law of fast up to the beginning of their sixtieth year. Nevertheless, pastors and parents are to see to it that minors who are not bound by the law of fast and abstinence are educated in an authentic sense of penance.
Canon 1253: It is for the conference of bishops to determine more precisely the observance of fast and abstinence and to substitute in whole or in part for fast and abstinence other forms of penance, especially works of charity and exercises of piety.