The "acceptable fast" is discussed in the biblical Book of Isaiah, chapter 58:3-7. In essence, it means afflict the soul through abstaining from fulfilling the needs or wants of the flesh. The opening chapter of the Book of Daniel, vv. 8-16, describes a partial fast and its effects on the health of its observers.

Fasting is a practice in several Christian denominations or other churches. Some denominations do not practice it, considering it an external observance, but many individual believers choose to observe fasts at various times at their own behest. The Lenten fast observed in the Catholic Church and the Eastern Orthodox Church is a forty-day partial fast to commemorate the fast observed by Christ during his temptation in the desert. This is similar to the partial fasting within the Ethiopian Orthodox Church (abstaining from meat and milk) which takes place during certain times of the year and lasts for weeks.