I was just recently asked if the Catholic Church still has the Eucharistic fast in place – and the answer is YES. Canon 919 of the "Code of Canon Law" states, "One who is to receive the Most Holy Eucharist is to abstain from any food or drink, with the exception of water and medicine, for at least the period of one hour before Holy Communion." Actually this regulation merely reflects an ancient tradition in our Church, which is even rooted in Judaism. For those who are elderly (at least 60 years of age) or sick as well as their caretakers can receive Communion even if a full hour fast has not been fulfilled. For example, people in the hospital are not in control of their own schedule and may be eating or have just finished eating when visited by the priest or Eucharistic minister. Therefore, the period of fast before receiving Holy Communion is reduced to "approximately one quarter of an hour" for those who are sick at home or at a medical facility, those elderly confined to home or a nursing home, and those who care for these people and who are unable conveniently to observe the fast ("Immensae Caritatis," 1973).
The fast before receiving Holy Communion creates a physical hunger and thirst for the Lord, which in turn augments the spiritual hunger and thirst we ought to have. In the Old Testament, fasting prepared individuals to receive the action of God and to be placed in His presence. For instance, Moses (Ex 34:28) fasted 40 days atop Mount Sinai as he received the Ten Commandments. Elijah (I Kings 19:8) fasted 40 days as he walked to Mount Horeb to encounter God. Similarly, Jesus Himself fasted 40 days as he prepared to begin His public ministry (Mt 4:1ff) and encouraged fasting (Mt 6:16-18).
This effort enhances the spiritual disposition we need to receive Christ in the Blessed Sacrament. In a sense, we fast so as not "to spoil our appetite" but to increase it for the sharing of the Eucharistic meal. Jesus said in the Beatitudes, "Blest are they who hunger and thirst for holiness; they shall have their fill" (Mt 5:6). In all, fasting is an exercise of humility, hope and love—essential virtues in preparing ourselves to receive the Holy Eucharist. This regulation, however, does not mean we have to be scrupulous and count off seconds. While we do not want to be lax, we do not want to be scrupulous. The goodness of receiving Holy Communion supersedes the precise "hour of fast" if there is doubt. A good rule of thumb is no food, candy, etc. at least 30 minutes prior to the start of Mass.
I encourage parents to talk to their children about this important fast and why we observe it. It is part of being Catholic. It is part of our tradition.