History of Lent
 
Second, the general rule was for a person to have one meal a day, in the evening or at 3 p.m.

These Lenten fasting rules also evolved. Eventually, a smaller repast was allowed during the day to keep up one's strength from manual labor. Eating fish was allowed, and later eating meat was also allowed through the week except on Ash Wednesday and Friday. Dispensations were given for eating dairy products if a pious work was performed, and eventually this rule was relaxed totally. (However, the abstinence from even dairy products led to the practice of blessing Easter eggs and eating pancakes on Shrove Tuesday, the day before Ash Wednesday.)

Over the years, modifications have been made to the Lenten observances, making our practices not only simple but also easy. Ash Wednesday still marks the beginning of Lent, which lasts for 40 days, not including Sundays. The present fasting and abstinence laws are very simple: On Ash Wednesday and Good Friday, the faithful fast (having only one full meal a day and smaller snacks to keep up one's strength) and abstain from meat; on the other Fridays of Lent, the faithful abstain from meat. People are still encouraged "to give up something" for Lent as a sacrifice. (An interesting note is that technically on Sundays and solemnities like St. Joseph's Day (March 19) and the Annunciation (March 25), one is exempt and can partake of whatever has been offered up for Lent.

Nevertheless, I was always taught, "If you gave something up for the Lord, tough it out. Don't act like a Pharisee looking for a loophole." Moreover, an emphasis must be placed on performing spiritual works, like attending the Stations of the Cross, attending Mass, making a weekly holy hour before the Blessed Sacrament, taking time for personal prayer and spiritual reading and most especially making a good confession and receiving sacramental absolution. Although the practices may have evolved over the centuries, the focus remains the same: to repent of sin, to renew our faith and to prepare to celebrate joyfully the mysteries of our salvation.
 
(Information Source - https://www.catholiceducation.org/en/culture/catholic-contributions/history-of-lent.html)