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. Now in the United States, the U.S. Bishops conference obtained the permission of the Holy See for Catholics in the US to substitute a penitential, or even a charitable, practice of their own choosing for the weekly Friday observance. However, during the time of Lent, the law of abstinence is applied for Fridays. This rule is for all Catholics 14 years of age and older. In honor of Our Lord's Passion, one is asked to refrain from eating meat.
Meat is considered to be the flesh and organs of mammals and fowl.
Also forbidden are soups or gravies made from them. Salt and freshwater species of fish, amphibians, reptiles and shellfish are permitted, as are animal derived products such as margarine and gelatin which do not have any meat taste. Also, on Ash Wednesday and Good Friday, Catholics from the ages of 18 to 59 are asked to fast. Fasting is defined as one meal a day, and two smaller meals which if added together would not exceed the main meal in quantity. The key is to use common sense, and to remember that your are fasting to show your love for God and to grow closer to the Creator.