Abstinence.

    All persons over seven years of age must abstain. This means that they may not take fleshmeat, meat gravy, or meat soup at all on days of complete abstinence, which are all Fridays (except on holydays of obligation), Ash Wednesday, Holy Saturday (until noon), and the Vigils of the Immaculate Conception and Christmas. By the decree of the Sacra Congregatio Concilii, dated December 3, 1959, the fast and abstinence of the Vigil of Christmas may, at the option of the individual, be anticipated on December 23.

    They may take meat, but only at the principal meal, on days of partial abstinence, which are Ember Wednesdays and Saturdays, and the Vigils of Pentecost and of All Saints' Day.

Fast.

    All persons over twenty-one and under fifty-nine years of age must fast. This means that on a fast day they may have only one principal or full meal and two smaller meals. They may eat meat at this principal meal, except on days of complete abstinence. At the two smaller meals they may not have meat, but they may take sufficient food to maintain their strength. However, these two smaller meals together should be less than a full meal. Eating between meals is not permitted, but liquids, including milk and fruit juices, may be taken any time on a fast day. The days of fast are the weekdays of Lent including Holy Saturday (until noon), the Ember Days, and the Vigils of Pentecost, the Immaculate Conception, All Saints' Day, and Christmas (or December 23).

    Those not bound to fast may eat meat as often as they wish, except on days of complete abstinence (when it may not be eaten at all), and on days of partial abstinence (when it may be eaten only at the principal meal). When a person's health or ability to work would be seriously affected by fasting or, in even rarer cases, by abstaining, a traditional priest/confessor should be consulted to determine whether the law obliges.

    In granting these concessions, the bishops urged the faithful:

• to attend daily Mass during the period of fast and abstinence [if this is not possible, one might say all or part of the Divine Office, the Little Office of the Blessed Virgin Mary, or the Most Holy Rosary]
• to receive Holy Communion often
• to take part more frequently in exercises of piety
• to give generously to works of religion and charity
• to perform acts of kindness toward the sick, the aged, and the poor
• to practice voluntary self-denial
• to pray more fervently

Eucharistic Fast.

    The fast to be observed before the celebration of Mass or the reception of Holy Communion is traditionally, from the early Church, a strict fast from all solid food and beverages, including water, from midnight preceding Mass.

    In 1956, Pope Pius XII limited the period of time for the observance of the Eucharistic fast before the celebration of Mass or the reception of Holy Communion, which some traditional Catholics follow, to three hours from solid food and alcoholic beverages, and to one hour from non-alcoholic beverages, not including water.

    In allowing this limitation, however, the pope stated: "We earnestly exhort the priests and faithful who are able to do so to observe the venerable and time-honored form of the Eucharistic fast before the celebration of Mass and the reception of Holy Communion" (Motu Proprio Sacram Communionem), that is, the strict fast from midnight. (traditio.com)