With the exception of Sundays, every day from Ash Wednesday until 12:00 noon on Holy Saturday is a day of fast and abstinence. Ash Wednesday, Holy Saturday and all Fridays are days of complete abstinence, and this applies to all persons seven years of age and older. All other fast days are days of partial abstinence. Fasting means taking only one full meal (called the principal meal) each day. Meat may be taken only at the principal meal on days of partial abstinence (on days of complete abstinence, of course, no meat is allowed.) The smaller meals together must not amount to the quantity of the principal meal. The requirements of partial abstinence and fasting apply to all persons from 21 to 59 years of age. Anyone who thinks his health or other condition might exempt him from the fast and abstinence of Lent should ask one of the priests. 

Note: Some people are confused by the rule governing the quantity of food allowed by the Lenten fast, especially because the need for nourishment varies so much from person to person. The spirit of the law requires that one avoid eating to the point of feeling "full," that one eat only enough to feel a bit hungry before the next meal. If a Catholic goes through Lent without experiencing hunger, he can be quite sure that he has not fulfilled the spirit of the Lenten law. If one feels a bit hungry, some, or even much of the time, he can be sure he's kept the spirit of the Lenten fast.