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Fasting is the act of willingly abstaining from all food and in some cases water, or in other cases from certain food groups.

Table of contents
1 Fasting for Religious Reasons
2 Fasting for Medical Reasons
3 The Internal Effects of Fasting
4 The Political Fast
5 See also:

Fasting for Religious Reasons

Fasting for spiritual reasons has been known for ages. It is mentioned in the Mahabharat, in the Upanishads, and in the Bible (in both the Old and New Testament).


In Hinduism, a religious fast is observed on ekadasi (the eleventh day of each lunar fortnight) and, if observed strictly, involves taking no food or water from the previous day's sunset until 48 minutes after the following day's sunrise.


In Islam, sunrise-to-sunset fasting is observed during the month of Ramadan.


Fasting is a practice in several Christian denominations. Other Christian denominations do not practice it because they see it as an external observence.

Roman Catholicism

Roman Catholics, fasting refers to those days set aside by the church when the faithful must reduce their intake of food to one full meal (which may contain meat) and two small meals (known liturgically as collations, taken in the morning and the evening) as distinct from abstinence which was the complete avoidance of meat on Fridays, especially during Lent.

Ash Wednesday and Good Friday are still days of fasting and abstinence, as specified in the Code of Canon Law (cc. 1250 to 1253). On these two solemn days Roman Catholics are enjoined to both fast (reduce the size of their daily meals) and to abstain (to completely avoid the consumption of meat in those meals).

The current regulations concerning Lenten fasting and abstience for Catholics in the United States generally are as follows,

For Catholics whose health or ability to work would be negatively affected by fasting and/or abstinence, the regulations above don't apply.

Until the Second Vatican Council Ash Wednesday and all the subsequent Fridays and Saturdays of Lent were days of "Fasting and Abstinence" whereas all the other weekdays of Lent were days of "Fasting without Abstinence". An exception to this rule was granted to the Bishops of Ireland (see Irish calendar) by the Vatican in 1918, when the obligation of fasting and abstaining on the Lenten Saturdays was transferred to the Wednesdays of Lent instead.

Immediately before the Second Vatican Council limited fasting to Ash Wednesday and Good Friday, fasting days included all of the weekdays (i.e., non-Sundays) of Lent, all Ember days, and the vigils of (days before) Pentecost, Immaculate Conception, and Christmas, unless either of the latter two fell on a Sunday (regardless of other circumstances, a Sunday could never be a day of fast or abstinence). Abstinence was required on all Fridays, except those upon which a holy day of obligation fell, and also on Ash Wednesday, Holy Saturday, and the vigils of Immaculate Conception and Christmas unless the latter two were Sundays. Prior to 1951, all Wednesdays of Lent and the vigils of Assumption and All Saints (unless Sunday) were also days of both fasting and abstinence (but the vigil of Immaculate Conception was not), and Ember days brought abstinence as well as fasting (the fast on the vigil of Pentecost was added in 1951, not having been in force prior).

In recent years, Saint Patrick's Day has at times fallen on a Friday of Lent. Some Priests have granted dispensations for their parishoners from the abstinence obligations so that Catholics could enjoy traditional Irish dishes.

Eastern Orthodox Churches

For Orthodox Christians, fasting at various times refers to abstention from animal products, olive oil (or all oils, according to some Orthodox traditions), wine and spirits -- see Eastern Orthodoxy (Fasting).

Protestant Churches

In Protestantism, the Reformers criticized fasting as a purely external observance that can never gain a person salvation. The Swiss Reformation of the "Third Reformer" Huldrych Zwingli began with an ostentatious public sausage-eating during Lent.


Observant Jews fast on 7 days during the Jewish calendar. Five of these are considered minor fast days: The Fast of Gedaliah, The Fast of Tevet, Tevet 10, The Fast of Esther, which takes place immediately before Purim & The Fast of the Firstborn, which takes place before Passover, and only applies to first-born sons. The second major fast day is Tisha B'Av, a 25-hour fast that mourns the destruction of the first and second Jewish_Temple, the Jewish expulsion from Spain, and other tragedies that have befallen the Jewish people. The second major fast day is Yom Kippur, also known as the Day of Repentence, which is considered the holiest day on the Jewish calendar.

Fasting for Medical Reasons

People can also fast for medical reasons, and this has also been an accepted practice for many years.

One reason that people fast for medical reasons is for surgery or other procedures that require anesthetic. Because the presence of food in a person's system can cause complications when they are anesthesied, medical personnel have people fast for several hours before the procedure.

Another reason that people fast for medical reasons is for certain medical tests. People are often asked to fast so that a baseline can be established.

Longer term fasting for health reasons typically lasts a week or longer and includes some food intake, such as fruit or vegetable juices.

Recent studies on mice show that fasting on every other day while eating double the amount on non-fasting days led to better insulin control, neuronal resistance to injury, and health indicators similar to mice on calorie restricted diets. This may mean that alternate-day fasting is an alternative to caloric restriction for life extension.

The Internal Effects of Fasting

Since your body consumes about one third of its total energy during the hours you are awake, your body is constantly requiring and using energy. When food is not eaten, the body looks for other ways to find energy, such as drawing on glucose from the liver's stored glycogen and fatty acids from stored fat and eventually moving on to vital protein tissues. The body is fine relying on fatty acids but the brain and the nerves depend on glucose. Once the glucose is significantly used up, the body switches and begins to produce ketone bodies (acetoactate, hydroxy-butyrate, and acetone. Even though this transformation to an alternative form of energy has been made, some parts of the brain exclusively need glucose and protein is still needed to produce it. If body protein loss were to continue, death will ensue.

The Political Fast

The political fast (today more commonly known as the hunger strike) seems to be an invention of Mohandas Gandhi. Some people see a difference between a hunger strike, a pure political act, and fasting, a political and religious act. By fasting, they intend to take some of the responsibility of the problem in question.

Hunger strikes have been used by personalities all over the world, including Martin Luther King Jr and Lanza del Vasto (during the Algerian War, Vatican II and the struggle of the farmers of the Larzac plateau).

Today, hunger strikes are often used by refugees seeking political asylum.

See also: