Water fasting

Water fasting is a type of fasting in which the practitioner consumes only water when he/she is thirsty. One may water fast for a variety of reasons, including health improvement and medical and religious requirements.

Health improvement
Some engage in water fasting as a detox diet. No energy is spent on digestion, other than to heat any cold water to reach homeostasis of a uniform body temperature. The fast is normally undergone with the intent of detoxification for greater health. The reasoning behind this is that less energy is expended on digestion of foods, resulting in more energy for the rest of the body to expel toxins as well as to recover and heal itself from the stresses digestion places upon it. Paul C. Bragg referred to this energy as the "Vital Force," and popularized water fasting with his many books, "Bragg Health Crusades," and success with Hollywood celebrities like Clint Eastwood Other proponents claim that protein sparing minimizes muscle loss as the body adapts to the lack of incoming protein by drawing upon almost solely fat for energy. Even so, metabolism will slow during an extended fast and physical/mental activity should be minimized for safety reasons.

Herbert M. Shelton, a proponent of Natural Hygiene, supervised patients on water fasts for up to ninety days over a period of 45 years. Shelton claimed the hunger experienced during the first three days of a fast are "gastric irritation" and not "true hunger."

Joel Fuhrman, MD, believes that many diseases can be reversed through pure water fasting. These include asthma, cardiovascular disease, high blood pressure, colitis, psoriasis and various auto-immune disorders.

Medical requirement
Historically, many surgeries and general anaesthetics required a patient to fast for up to half a day before the procedure. This is thought to reduce potential complications of stomach volume and acidity during the procedure. However, growing research suggests that patients, especially children, may do better if they consume water or clear liquid during the final hours of this fast.

Religious requirement
Fasting in Jainism

Jains maintain a strict only water fast for 8 days, during the days of Paryushan. The warm water consumed should be only between sunrise and sunset and not during the night, since night is a high time for micro-organismic activity. Jains are strict disciplinarians and believe in non-violence. For Jains fasting is a way of penance.

Fasting in the Catholic Church

Roman Catholics must engage in the Eucharistic Fast, which is a water fast before receiving the Eucharist during the Mass. While no nutritional or caloric sustenance is permitted, practitioners may take medicine if required, and those whose health problems impede them from taking part in the fast are dispensed of the obligation.

Up until the reforms of the Second Vatican Council, this fast was required from the previous midnight, as it is in various Orthodox Churches. However, under the Holy Father Paul VI, the obligatory fast was reduced to only one hour before receiving the Eucharist.

The Catholic Church has also promoted a Black Fast, in which in addition to water, bread is consumed. Typically, this form of fasting was only used by monks and religious who practice mortifications and asceticism, but all Catholics are invited to take part in it with the advice and consent of their Spiritual Director.

Fasting in Islam

Muslims are required to fast from dawn to sunset (avoiding food and drink) during the month of Ramadan.

Fasting in Judaism

Jews fast (avoiding food or drink) multiple times throughout a calendar year. Yom Kippur and Tishah B'Av are full day fasts that begin at sunset and end the next day at sunset. Ta'anit Bechorim, Tzom Tammuz, Tzom Gedalia, Asarah B'Tevet and Ta'anit Esther are half day fasts that begin at sunrise and end at sunset on the same day.