Fasting and abstinence on Ash Wednesday and Good Friday:  Fasting consists of eating only one meal, with the possibility of two smaller snacks that do not add up to a single full meal.  Catholics in good health ages 18 to 59 are required to fast and to abstain from meat on Ash Wednesday and Good Friday and to abstain from meat all other Fridays in Lent.  Youth 13 and older are to abstain from meat on these days.

Abstinence from meat on Fridays:  Canon 1251 specifies that Catholics refrain from eating meat on Fridays, as an act of penitence.  In the US, Catholics are permitted to substitute another penance outside of the season of Lent.  During Lent, however, all Catholics are obliged not to eat meat on Fridays.

Penance during Lent:  The season of Lent is a penitential time and should also be marked by some additional form of self-denial.