Some 21-day fasts are the Complete Fast, Selective Fast, Partial Fast and Soul Fast, notes Church of the Highlands. Many Christian churches take part in one form of 21-day fast in January to symbolize Daniel's 21-day fast in the Old Testament. The Selective Fast is also known as the Daniel Fast.
Parishioners who choose to follow the Complete Fast are allowed only water and light juices during the 21 days. The Selective Fast requires followers to remove certain items from their diets. The excluded items are typically meat, sweets and bread. The Partial Fast, also known as the Jewish Fast, requires parishioners to fast in the morning and afternoon. The Soul Fast is an option for people who cannot fast for health reasons. They can choose to remove another element from their life for the fasting period, such as television.