On Fasting and Abstinence
Bishop Fulton Sheen told of his experience one Lenten season while on a plane to a speaking engagement. When the flight attendant offered him his lunch, he excused himself saying, "I'll just have a sandwich, it's Lent.". The woman beside him also settled for just a sandwich. "So you're also Catholic," Bishop Sheen asked. The woman with a surprised look said, "No, I'm a model."
Here are some key things to consider on fasting and abstinence, from the 1983 Code of Canon Law:
Canon 1250 All Fridays through the year and the time of Lent are penitential days and times throughout the entire Church.
Canon 1251 Abstinence from eating meat or another food according to the prescriptions of the conference of bishops is to be observed on Fridays throughout the year unless they are solemnities; abstinence and fast are to be observed on Ash Wednesday and on the Friday of the Passion and Death of Our Lord Jesus Christ.
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.
And here is some food for thought. Fasting is a form of spiritual discipline where our aim is beatification. The discipline of Lent can never be dissociated with discipleship. Discipline without discipleship is like practicing for a marathon without running it. Discipleship without discipline is running a marathon without practicing.
Finally, here is a nice graphic, courtesy of the Curt Jester.