Fasting & Abstinence
Fasting and abstinence are closely related, but there are some differences in these spiritual practices. In general, fasting refers to restrictions on the quantity of the food we eat and on when we consume it, while abstinence refers to the avoidance of particular foods. The most common form of abstinence is the avoidance of meat, a spiritual practice that goes back to the earliest days of the Church.
Depriving Ourselves of Something Good:
Until the Second Vatican Council, Catholics were required to abstain from meat every Friday, as a form of penance in honor of the death of Jesus Christ on the Cross on Good Friday. In the Acts of the Apostles (Acts 10:9-16), St. Peter has a vision in which God reveals that Christians can eat any food. So, when we abstain, it is not because the food is impure; we are voluntarily giving up something good, for our spiritual benefit.
Under current Church law, the days of abstinence fall during Lent, the season of spiritual preparation for Easter. On Ash Wednesday and all of the Fridays of Lent, Catholics over the age of 14 are required to abstain from meat and from foods made with meat (this includes gravies and soups made from meat stock).
Many Catholics do not realize that the Church still recommends abstinence on all Fridays of the year, not just during Lent. In fact, if we do not abstain from meat on non-Lenten Fridays, we are required to substitute some other form of penance. On the Fridays outside of Lent the U.S. bishops obtained permission for Catholics to substitute a penitential, or even a charitable practice of their own choosing. For most people the easiest practice to consistently fulfill will be the traditional one, to abstain from meat on all Fridays of the year.
Going Beyond What's Required:
If you would like to make abstinence a bigger part of your spiritual discipline, a good place to start is to abstain from meat on all Fridays of the year. During Lent, you might consider following the traditional rules for Lenten abstinence, which include eating meat at only one meal per day (in addition to strict abstinence on Ash Wednesday and Fridays).
Unlike fasting, abstinence is less likely to be harmful if taken to extremes, but, if you want to extend your discipline beyond what the Church currently prescribes (or beyond what it has prescribed in the past), you may want to consult a priest.