The practice of Christian fasting goes back to the early church, and even into the Old Testament. The days and rules varied over the centuries, and even today many Catholics abstain from meat on Fridays all year. This led to the tradition of schools serving fish sticks on Fridays, and the invention of the McDonald's Filet-o-Fish.
Americans who are not Catholic are most familiar with the practice of Friday fasting during Lent, the 40-day period before Easter, when many churches hold Friday fish fries. But why fish? The early church defined "meat" as the flesh of a warmblooded animal, which means fish is not included. Saint Thomas Aquinas went into more detail about the difference between fish and meat. You may have heard that a medieval pope launched that rule in cahoots with fish producers. There is no evidence that the conspiracy ever happened, but the church rules about fasting had a big impact on the fishing industry, due to rising demand from Christians who lived far from the sea.
However, the rules were drawn up with the purpose of encouraging penitence and meditation, and were adjusted to local conditions. The church offered dispensations for the flesh of various animals such as beaver, alligator, cabybara, muskrat, armadillo, iguana, and puffins. However, these dispensations apply only to certain geographical areas, and some have expired as conditions changed.
Today, the Catholic church encourages fasting, but it is voluntary and may be substituted with prayers and charitable works. Some Protestant churches encourage each person to give something up during Lent, but the choice of sacrifice is personal. Meanwhile, everyone's invited to the Friday fish fry, because they are a nice social event for everyone, and often raise funds for charities.
(Image credit: Jon Sullivan)