To fast means to limit the quantity of food. To abstain means to refrain from eating meat.
Ash Wednesday and Good Friday are days of fast and abstinence, and all Fridays of Left are days of abstinence.
The obligation to abstain from meat brands Catholics 14 years of age and older. The obligation to fast, limiting oneself to one full meal and two lighter meals in the course of a day, binds Catholics from the ages of 21 to 59.
Those who are sick (this includes pregnant women) are not obliged to fast, ( In doubt about other reasons, consult your confessor.)
Fasting and abstaining are forms of penance. As followers of Christ we are to participate in the sufferings of Christ. Other Voluntary forms should also be practiced. Prayer can be penitential, both private and liturgical. Charity toward the neighbor calls for surrender of self-love and the sharing of oneâ€™s possessions.