fasting, abstinence fromfood or drink or both forhealth, ritualistic, religious, orethical purposes. The abstention may be complete or partial, lengthy, of short duration, orintermittent. Fasting has been promoted and practiced from antiquity worldwide by physicians, by the founders and followers of many religions, by culturally designated individuals (e.g., hunters or candidates for initiation rites), and by individuals or groups as an expression of protest against what they believe are violations of social, ethical, or political principles.

Medical fasting

Fasting has been used therapeutically since at least the 5th centurybce, when Greek physicianHippocrates recommended abstinence from food or drink for patients who exhibited certain symptoms of illness. Some physicians recognized a fasting instinct, whereby patients in certain disease states naturally experience a loss ofappetite. Some physicians believed that administering food during such states was unnecessary and possibly evendetrimental, since fasting was thought to be an important natural part of the recovery process.

An understanding of the physiological effects of fasting began to evolve in the latter part of the 19th century, when some of the first organized studies of fasting were carried out in animals and humans. In the 20th century, as more became known about nutrition and the nutritional requirements of thehuman body, methods of fasting became increasingly sophisticated, and a wide array of approaches emerged. For example, fasting was used as a treatment and as a form of disease prevention, and it was carried out in various settings (e.g., in a hospital or clinic or at home). Some fasting methods, particularly those applied in the treatment of chronic diseases, lasted more than a month, allowed for theconsumption of only water orcalorie-free tea, and included exercise andenemas. Other methods, generally referred to as modified fasting, allowed for the intake of 200 to 500 kilocalories per day (daily calorie needs of adults range from about 1,600 to 3,000 kilocalories, depending on sex, age, and activity level) and sometimes included psychological or spiritual therapy; depending on the particular method used, calories usually were in the form of bread, vegetable broth, fruit juice, honey, or milk. Modified fasting was distinguished from a very low-calorie diet, which allowed up to 800 kilocalories per day and typically was aimed at inducing substantial weight loss. Intermittent fasting involved cyclic periods of calorie restriction, such as a 24-hour period of fasting followed by a 24-hour period of regular calorie consumption.

More From Britannica

Judaism: The five fasts

By the 21st century, although fasting clearly was applicable in some instances of disease, such as in certainacute diseases (particularly when accompanied by a loss of appetite), whether fasting in other instances wasbeneficial to human health remained unclear. For example, whereas research in humans had suggested that intermittent fasting carried out over 15 days improved insulin-mediated glucose uptake into tissues, studies in rodents had indicated that such fasting, carried out over the long-term, promoted glucose intolerance and the release of damaging oxidants from tissues.

Fasting and religion

In the religions of ancient peoples and civilizations, fasting was a practice to prepare persons, especially priests and priestesses, to approach the deities. In the Hellenisticmystery religions (e.g., thehealing cult of the godAsclepius), the gods were thought to reveal their divine teachings in dreams and visions only after a fast that required the total dedication of the devotees. Among the pre-Columbian peoples of Peru, fasting often was one of the requirements for penance after an individual had confessed sins before a priest. In manycultures the practice was considered a means toassuage an angered deity or to aid in resurrecting a deity who was believed to have died (e.g., a god of vegetation).

In the religions of some tribes ofNative Americans, fasting was practiced before and during avision quest. Among theEvenk of Siberia, shamans (religious personages thought to have the power to heal and to communicate psychically) often received their initial visions not with a quest but rather after an unexplained illness. After the initial vision, however, they fasted and trained themselves to see further visions and to control spirits. Historically, priestly societies among thePueblo Indians of the American Southwest fasted during retreats before major ceremonies connected with seasonal changes.

Fasting for special purposes or before or during special sacred times remains a characteristic of major religions of the world. InJainism, for example, fasting according to certain prescribed rules and practicing certain types ofmeditation leads to trances that enable individuals to dissociate themselves from the world and reach atranscendent state. Some Buddhist monks of theTheravada school fast as part of their meditation practices. InIndia, Hindu sadhus (holy men) are admired for their frequent personal fasts for various reasons.

Get Unlimited Access

Try Britannica Premium for free and discover more.

Subscribe

Among the Western religions, onlyZoroastrianism prohibits fasting, because of its belief that such a form ofasceticism will not aid in strengthening the faithful in their struggle against evil. The other Western religions—Judaism,Christianity, andIslam—emphasize fasting during certain periods.Judaism, which developed many dietary laws and customs, observes several annual fast days, primarily on days of penitence (such asYom Kippur, the Day of Atonement) ormourning. Christianity, especiallyRoman Catholicism andEastern Orthodoxy, has observed a 40-day fast period duringLent, a spring period of penitence beforeEaster, and duringAdvent, a penitential period beforeChristmas. Among Roman Catholics the observance has been modified since theSecond Vatican Council (1962–65) to allow greater individual choice, withmandatory fasting only onAsh Wednesday andGood Friday during Lent. Protestant churches generally leave the decision to fast to individual church members. The month ofRamadan in Islam is a period of penitence and total fasting from dawn to dusk.

Fasting as a form of protest

In addition to its role inreligion, fasting may be used to express social and political views, particularly as a gesture of protest or solidarity. The classic example of this approach was set byMahatma Gandhi, who in the early 20th century conducted a fast in prison to atone for the violent excesses of those of his followers who did not practice his teaching ofsatyagraha (nonviolence) against British rule in India. Gandhi later often fasted in pursuit of similar objectives, including the removal of disabilitiesimposed by the government on theuntouchables. Fasting has frequently been practiced to protest against war and what are considered social evils and injustices, as in the fasts of the American black comedianDick Gregory from the 1960s in protest against the violation ofcivil rights of American Indians and against U.S. military activity inSoutheast Asia. In 1981, 10 Irish nationalists died in a Belfast prison during ahunger strike conducted to urge recognition of themselves and their associates as political prisoners.