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Fasting is the abstention from eating and sometimes drinking. From a purely
physiological Physiology (; ) is the scientific study of functions and mechanisms in a living system. As a sub-discipline of biology, physiology focuses on how organisms, organ systems, individual organs, cells, and biomolecules carry out the chemical ...
context, "fasting" may refer to the metabolic status of a person who has not eaten overnight (see "
Breakfast Breakfast is the first meal of the day usually eaten in the morning. The word in English refers to breaking the fasting period of the previous night.Anderson, Heather Arndt (2013)''Breakfast: A History'' AltaMira Press. Various "typical" or "t ...
"), or to the metabolic state achieved after complete
digestion Digestion is the breakdown of large insoluble food molecules into small water-soluble food molecules so that they can be absorbed into the watery blood plasma. In certain organisms, these smaller substances are absorbed through the small intes ...
and
absorption Absorption may refer to: Chemistry and biology *Absorption (biology), digestion **Absorption (small intestine) *Absorption (chemistry), diffusion of particles of gas or liquid into liquid or solid materials *Absorption (skin), a route by which s ...
of a meal. Metabolic changes in the fasting state begin after absorption of a meal (typically 3–5 hours after eating). A
diagnostic fast Hypoglycemia, also called low blood sugar, is a fall in blood sugar to levels below normal, typically below 70 mg/dL (3.9 mmol/L). Whipple's triad is used to properly identify hypoglycemic episodes. It is defined as blood glucose belo ...
refers to prolonged fasting from 1 to 100 hours (depending on age) conducted under observation to facilitate the investigation of a health complication, usually
hypoglycemia Hypoglycemia, also called low blood sugar, is a fall in blood sugar to levels below normal, typically below 70 mg/dL (3.9 mmol/L). Whipple's triad is used to properly identify hypoglycemic episodes. It is defined as blood glucose belo ...
. Many people may also fast as part of a medical procedure or a check-up, such as preceding a
colonoscopy Colonoscopy () or coloscopy () is the endoscopic examination of the large bowel and the distal part of the small bowel with a CCD camera or a fiber optic camera on a flexible tube passed through the anus. It can provide a visual diagnosis (''e ...
or surgery, or before certain medical tests. Intermittent fasting is a technique sometimes used for
weight loss Weight loss, in the context of medicine, health, or physical fitness, refers to a reduction of the total body mass, by a mean loss of fluid, body fat (adipose tissue), or lean mass (namely bone mineral deposits, muscle, tendon, and other co ...
that incorporates regular fasting into a person's dietary schedule. Fasting may also be part of a religious ritual, often associated with specifically scheduled fast days, as determined by the religion.


Health effects

Fasting may have different results on health in different circumstances. To understand whether loss of appetite (
anorexia Anorexia nervosa, often referred to simply as anorexia, is an eating disorder characterized by low weight, food restriction, body image disturbance, fear of gaining weight, and an overpowering desire to be thin. ''Anorexia'' is a term of Gre ...
) during illness was protective or detrimental, researchers in the laboratory of
Ruslan Medzhitov Ruslan Maksutovich Medzhitov (born March 12, 1966) is a professor of immunobiology at Yale School of Medicine, a member of Yale Cancer Center, and a Howard Hughes Medical Institute investigator. His research focuses on the analysis of the innate ...
at Yale School of Medicine gave carbohydrate to mice with a bacterial or viral illness, or deprived them of carbohydrate. They found that carbohydrate was detrimental to bacterial
sepsis Sepsis, formerly known as septicemia (septicaemia in British English) or blood poisoning, is a life-threatening condition that arises when the body's response to infection causes injury to its own tissues and organs. This initial stage is follo ...
. But with viral sepsis or influenza, nutritional supplementation with carbohydrates was beneficial, decreasing mortality, whereas denying glucose to the mice, or blocking its metabolism, was lethal. The researchers put forth hypotheses to explain the findings and called for more research on humans to determine whether our bodies react similarly, depending on whether an illness is bacterial or viral. Alternate-day fasting (alternating between a 24-hour "fast day" when the person eats less than 25% of usual energy needs, followed by a 24-hour non-fasting "feast day" period) has been shown to improve
cardiovascular The blood circulatory system is a system of organs that includes the heart, blood vessels, and blood which is circulated throughout the entire body of a human or other vertebrate. It includes the cardiovascular system, or vascular system, t ...
and metabolic
biomarker In biomedical contexts, a biomarker, or biological marker, is a measurable indicator of some biological state or condition. Biomarkers are often measured and evaluated using blood, urine, or soft tissues to examine normal biological processes, pa ...
s similarly to a
calorie restriction diet Calorie restriction (caloric restriction or energy restriction) is a dietary regimen that reduces intake of energy from caloric foods & beverages without incurring malnutrition. "Reduce" can be defined relative to the subject's previous intake b ...
in people who are overweight, obese or have metabolic syndrome. A 2021 review found that moderate alternate-day fasting for two to six months was associated with reductions of body weight,
body mass index Body mass index (BMI) is a value derived from the mass (weight) and height of a person. The BMI is defined as the body mass divided by the square of the body height, and is expressed in units of kg/m2, resulting from mass in kilograms and hei ...
, and cardiometabolic risk factors in overweight or obese adults.


Medical application

Fasting is always practised prior to surgery or other procedures that require general anesthesia because of the risk of pulmonary aspiration of gastric contents after induction of anesthesia (i.e., vomiting and inhaling the vomit, causing life-threatening
aspiration pneumonia Aspiration pneumonia is a type of lung infection that is due to a relatively large amount of material from the stomach or mouth entering the lungs. Signs and symptoms often include fever and cough of relatively rapid onset. Complications may inclu ...
). Additionally, certain medical tests, such as cholesterol testing ( lipid panel) or certain blood glucose measurements require fasting for several hours so that a baseline can be established. In the case of a lipid panel, failure to fast for a full 12 hours (including vitamins) will guarantee an elevated triglyceride measurement.


Mental health

In one review, fasting improved
alertness Alertness is the state of active attention by high sensory awareness such as being watchful and prompt to meet danger or emergency, or being quick to perceive and act. It is related for psychology . A lack of alertness is a symptom of a ...
, mood, and subjective feelings of well-being, possibly improving overall symptoms of depression, and boosting cognitive performance.


Weight loss

Intermittent fasting for periods shorter than 24 hours has been shown to be effective for
weight loss Weight loss, in the context of medicine, health, or physical fitness, refers to a reduction of the total body mass, by a mean loss of fluid, body fat (adipose tissue), or lean mass (namely bone mineral deposits, muscle, tendon, and other co ...
in obese and healthy adults and to maintain lean body mass.


Complications

In rare occurrences, dry fasting can lead to the potentially fatal refeeding syndrome upon reinstatement of food intake due to electrolyte imbalance.


Historical medical studies

Fasting was historically studied on population under famine and hunger strikes, which led to the alternative name of "starvation diet", as a diet with 0 calories intake per day.


Other effects

It has been argued that fasting makes one more appreciative of food, and possibly drink.


Political application

Fasting is often used to make a political statement, to protest, or to bring awareness to a cause. A hunger strike is a method of
non-violent resistance Nonviolent resistance (NVR), or nonviolent action, sometimes called civil resistance, is the practice of achieving goals such as social change through symbolic protests, civil disobedience, economic or political noncooperation, satyagraha, const ...
in which participants fast as an act of political protest, or to provoke feelings of guilt, or to achieve a goal such as a policy change. A ''spiritual fast'' incorporates personal spiritual beliefs with the desire to express personal principles, sometimes in the context of social injustice.Garcia, M. (2007) ''The Gospel of Cesar Chavez: My Faith in Action'' Sheed & Ward Publishing p. 103 The political leader Gandhi undertook several long fasts as political and social protests. Gandhi's fasts had a significant impact on the
British Raj The British Raj (; from Hindi ''rāj'': kingdom, realm, state, or empire) was the rule of the British Crown on the Indian subcontinent; * * it is also called Crown rule in India, * * * * or Direct rule in India, * Quote: "Mill, who was himsel ...
and the
Indian Indian or Indians may refer to: Peoples South Asia * Indian people, people of Indian nationality, or people who have an Indian ancestor ** Non-resident Indian, a citizen of India who has temporarily emigrated to another country * South Asia ...
population generally. In Northern Ireland in 1981, a prisoner,
Bobby Sands Robert Gerard Sands ( ga, Roibeárd Gearóid Ó Seachnasaigh; 9 March 1954 – 5 May 1981) was a member (and leader in the Maze prison) of the Provisional Irish Republican Army (IRA) who died on hunger strike while imprisoned at HM Prison Maze ...
, was part of the
1981 Irish hunger strike The 1981 Irish hunger strike was the culmination of a five-year protest during the Troubles by Irish republican prisoners in Northern Ireland. The protest began as the blanket protest in 1976, when the British government withdrew Special Ca ...
, protesting for better rights in prison. Sands had just been elected to the British Parliament and died after 66 days of not eating. 100,000 people attended his funeral, and the strike ended only after nine other men died. In all, ten men survived without food for 46 to 73 days.
César Chávez Cesar Chavez (born Cesario Estrada Chavez ; ; March 31, 1927 – April 23, 1993) was an American labor leader and civil rights activist. Along with Dolores Huerta, he co-founded the National Farm Workers Association (NFWA), which later merge ...
undertook several spiritual fasts, including a 25-day fast in 1968 promoting the principle of nonviolence and a fast of 'thanksgiving and hope' to prepare for pre-arranged civil disobedience by farm workers.Shaw, R. (2008)''Beyond the Fields: Cesar Chavez, the UFW, and the struggle for justice in the 21st century'' University of California Press, p.92 Chávez regarded a spiritual fast as "a personal spiritual transformation". Other progressive campaigns have adopted the tactic.


Religious views

Fasting is practiced in various religions. Examples include Lent in Christianity;
Yom Kippur Yom Kippur (; he, יוֹם כִּפּוּר, , , ) is the holiest day in Judaism and Samaritanism. It occurs annually on the 10th of Tishrei, the first month of the Hebrew calendar. Primarily centered on atonement and repentance, the day's ...
, Tisha B'av,
Fast of Esther The Fast of Esther (', he, תַּעֲנִית אֶסְתֵּר) is a fast from dawn until dusk on Purim eve. This fast, unlike other fasts is a custom. Unlike the other fasts in Judaism, it is not mentioned in the Talmud, but only in the Midrash ...
, Tzom Gedalia, the
Seventeenth of Tamuz , observedby = Jews , date = 17th day of Tammuz , observances = Fasting, prayer , type = Jewish religious and national , significance = Date when the walls of Jerusalem were breached , relatedto = The fasts of the Tenth of Tevet and Tisha B'Av, ...
, and the Tenth of Tevet in Judaism. Muslims fast during the month of Ramadan each year. The fast includes refraining from consuming any food or liquid from sun up until sundown. Details of fasting practices differ. Eastern Orthodox Christians fast during specified fasting seasons of the year, which include not only the better-known Great Lent, but also fasts on every Wednesday and Friday (except on special holidays), together with extended fasting periods before Christmas (the
Nativity Fast In Christianity, the Nativity Fast—or Fast of the Prophets in Ethiopian Orthodox Tewahedo Church and Eritrean Orthodox Tewahedo Church—is a period of abstinence and penance practiced by the Eastern Orthodox Church, Oriental Orthodox Church a ...
), after Easter (the
Apostles Fast The Apostles' Fast, also called the Fast of the Holy Apostles, the Fast of Peter and Paul, or sometimes St. Peter's Fast, is a fast observed by Eastern Orthodox, Oriental Orthodox, Eastern Catholic, and Reformed Orthodox Christians. In the Byzant ...
) and in early August (the
Dormition Fast The Dormition of the Mother of God is a Great Feast of the Eastern Orthodox, Oriental Orthodox, and Eastern Catholic Churches (except the East Syriac churches). It celebrates the "falling asleep" (death) of Mary the ''Theotokos'' ("Mother of ...
). Members of the
Church of Jesus Christ of Latter-day Saints The Church of Jesus Christ of Latter-day Saints, informally known as the LDS Church or Mormon Church, is a nontrinitarian Christian church that considers itself to be the restoration of the original church founded by Jesus Christ. The chu ...
( Mormons) generally abstain from food and drink for two consecutive meals in a 24-hour period on the first Sunday of each month.https://www.churchofjesuschrist.org/bc/content/ldsorg/topics/fasting-and-fast-offerings/PD60001350_TMP_2016%20LeadMtg_The%20Law%20of%20the%20Fast_9-15-16%20KW.pdf Like Muslims, they refrain from all drinking and eating unless they are children or are physically unable to fast. Fasting is also a feature of
ascetic Asceticism (; from the el, ἄσκησις, áskesis, exercise', 'training) is a lifestyle characterized by abstinence from sensual pleasures, often for the purpose of pursuing spiritual goals. Ascetics may withdraw from the world for their p ...
traditions in religions such as Hinduism and
Buddhism Buddhism ( , ), also known as Buddha Dharma and Dharmavinaya (), is an Indian religion or philosophical tradition based on teachings attributed to the Buddha. It originated in northern India as a -movement in the 5th century BCE, and gra ...
. Mahayana traditions that follow the Brahma's Net Sutra may recommend that the laity fast "during the six days of fasting each month and the three months of fasting each year". Members of the
Baháʼí Faith The Baháʼí Faith is a religion founded in the 19th century that teaches the essential worth of all religions and the unity of all people. Established by Baháʼu'lláh in the 19th century, it initially developed in Iran and parts of the ...
observe a Nineteen Day Fast from sunrise to sunset during March each year.


In alternative medicine

Although practitioners of
alternative medicine Alternative medicine is any practice that aims to achieve the healing effects of medicine despite lacking biological plausibility, testability, repeatability, or evidence from clinical trials. Complementary medicine (CM), complementary and alt ...
promote " cleansing the body" through fasting, the concept of "detoxification“ is marketing myth with few scientific basis for its rationale or efficacy. During the early 20th century, fasting was promoted by alternative health writers such as
Hereward Carrington Hereward Carrington (17 October 1880 – 26 December 1958) was a well-known British-born American investigator of psychic phenomena and author. His subjects included several of the most high-profile cases of apparent psychic ability of his times, ...
, Edward H. Dewey,
Bernarr Macfadden Bernarr Macfadden (born Bernard Adolphus McFadden, August 16, 1868 – October 12, 1955) was an American proponent of physical culture, a combination of bodybuilding with nutritional and health theories. He founded the long-running magazine pub ...
, Frank McCoy,
Edward Earle Purinton Edward Earle Purinton (April 24, 1878 – July 10, 1943) was an American businessman, naturopath, philosopher and self-help writer. Biography Purinton was born in Morgantown, West Virginia. He obtained his Bachelor of Arts from Denison Univer ...
,
Upton Sinclair Upton Beall Sinclair Jr. (September 20, 1878 – November 25, 1968) was an American writer, muckraker, political activist and the 1934 Democratic Party nominee for governor of California who wrote nearly 100 books and other works in seve ...
and
Wallace Wattles Wallace Delois Wattles (; 1860 – 7 February 1911) was an American New Thought writer. He remains personally somewhat obscure, but his writing has been widely quoted and remains in print in the New Thought and self-help movements. Wattles' bes ...
.Griffith, R. Marie. (2000). ''Apostles of Abstinence: Fasting and Masculinity during the Progressive Era''. ''
American Quarterly ''American Quarterly'' is an academic journal and the official publication of the American Studies Association. The journal covers topics of both domestic and international concern in the United States and is considered a leading resource in the ...
'' 52 (4): 599-638.
All of these writers were either involved in the natural hygiene or new thought movement.
Arnold Ehret Arnold Ehret (July 29, 1866 October 10, 1922)Melton, Gordon J. (1990). ''New Age Encyclopedia''. Gale Research. p. 159. was a German naturopath and alternative health educator, best known for developing the Mucusless Diet Healing System. Ehret ...
's pseudoscientific Mucusless Diet Healing System espoused fasting.Kuske, Terrence T. (1983)
''Quackery and Fad Diets''
. In Elaine B. Feldman. ''Nutrition in the Middle and Later Years''. John Wright & Sons. pp. 291-303.
Linda Hazzard Linda Laura Hazzard (''née'' Burfield; December 18, 1867 – June 24, 1938), nicknamed the "Starvation Doctor" was an American quack, swindler and convicted serial killer noted for her promotion of fasting, pummeling and hours-long enemas as t ...
, a notable quack doctor, put her patients on such strict fasts that some of them died of
starvation Starvation is a severe deficiency in caloric energy intake, below the level needed to maintain an organism's life. It is the most extreme form of malnutrition. In humans, prolonged starvation can cause permanent organ damage and eventually, ...
. She was responsible for the death of more than 40 patients under her care. In 1911,
Upton Sinclair Upton Beall Sinclair Jr. (September 20, 1878 – November 25, 1968) was an American writer, muckraker, political activist and the 1934 Democratic Party nominee for governor of California who wrote nearly 100 books and other works in seve ...
authored '' The Fasting Cure'', which made sensational claims of fasting curing practically all diseases, including cancer,
syphilis Syphilis () is a sexually transmitted infection caused by the bacterium ''Treponema pallidum'' subspecies ''pallidum''. The signs and symptoms of syphilis vary depending in which of the four stages it presents (primary, secondary, latent, and ...
, and tuberculosis.Gratzer, Walter. (2005). ''Terrors of the Table: The Curious History of Nutrition''. Oxford University Press. p. 201. Sinclair has been described as "the most credulous of faddists" and his book is considered an example of quackery. In 1932, physician
Morris Fishbein Morris Fishbein M.D. (July 22, 1889 – September 27, 1976) was an American physician and editor of the ''Journal of the American Medical Association'' (''JAMA'') from 1924 to 1950. Ira Rutkow's ''Seeking the Cure: A History of Medicine in ...
listed fasting as a
fad diet A fad diet is a diet that becomes popular for a short time, similar to fads in fashion, without being a standard dietary recommendation, and often making unreasonable claims for fast weight loss or health improvements. There is no single defin ...
and commented that "prolonged fasting is never necessary and invariably does harm".Fishbein, Morris. (1932)
''Fads and Quackery in Healing: An Analysis of the Foibles of the Healing Cults''
New York: Covici Friede. p. 253


See also

*
Angus Barbieri's fast Angus Barbieri (1939 – 7 September 1990) was a Scottish man who fasted for 382 days, from June 1965 to July 1966. He lived on tea, coffee, soda water, and vitamins while living at home in Tayport, Scotland, and frequently visiting Maryfield ...
*
Anorexia mirabilis Anorexia mirabilis, also known as holy anorexia or inedia prodigiosa or colloquially as fasting girls, is an eating disorder, similar to that of anorexia nervosa, that was common in, but not restricted to, the Middle Ages in Europe, largely affect ...
*
Anorexia nervosa Anorexia nervosa, often referred to simply as anorexia, is an eating disorder characterized by low weight, food restriction, body image disturbance, fear of gaining weight, and an overpowering desire to be thin. ''Anorexia'' is a term of Gre ...
*
Asceticism Asceticism (; from the el, ἄσκησις, áskesis, exercise', 'training) is a lifestyle characterized by abstinence from sensual pleasures, often for the purpose of pursuing spiritual goals. Ascetics may withdraw from the world for their p ...
*
Autophagy Autophagy (or autophagocytosis; from the Ancient Greek , , meaning "self-devouring" and , , meaning "hollow") is the natural, conserved degradation of the cell that removes unnecessary or dysfunctional components through a lysosome-dependent r ...
*
Black Fast A Black Fast, also known as a strict fast, is an ancient form of Christian fasting. Those undertaking a Black Fast consume no food during the day (although sometimes water is permitted) and then break the fast after sunset with prayer, as well as ...
*
Break fast A break-fast is a meal eaten after fasting. In Judaism, a break fast is the meal eaten after Ta'anit (religious days of fasting), such as Yom Kippur. During a Jewish fast, no food or drink is consumed, including bread and water. The two major fa ...
* Calorie restriction * Fasting in Jainism *
Force-feeding Force-feeding is the practice of feeding a human or animal against their will. The term ''gavage'' (, , ) refers to supplying a substance by means of a small plastic feeding tube passed through the nose ( nasogastric) or mouth (orogastric) into t ...
* Inedia * Ketosis * List of diets *
List of fasting advocates Pseudoscientific advocates of fasting, not to be confused with fasting researchers. Fasting Pseudoscientific diet advocates ...
*
List of ineffective cancer treatments This is a non-exhaustive list of alternative treatments that have been promoted to treat or prevent cancer in humans but which lack scientific and medical evidence of effectiveness. In many cases, there is scientific evidence that the alleged tr ...
* Poustinia *
Protein-sparing modified fast A protein-sparing modified fast or PSMF diet is a type of a very-low-calorie diet (<800 kcal per day) with a high proportion of protein calories and simultaneous restriction of carbohydrate and fat. It includes a Santhara ''Sallekhana'' (IAST: ), also known as ''samlehna'', ''santhara'', ''samadhi-marana'' or ''sanyasana-marana'', is a supplementary vow to the ethical code of conduct of Jainism. It is the religious practice of voluntarily fasting to death by ...
* Simple living *
Starvation Starvation is a severe deficiency in caloric energy intake, below the level needed to maintain an organism's life. It is the most extreme form of malnutrition. In humans, prolonged starvation can cause permanent organ damage and eventually, ...
*
Starvation response Starvation response in animals (including humans) is a set of adaptive biochemical and physiological changes, triggered by lack of food or extreme weight loss, in which the body seeks to conserve energy by reducing the amount of calories it burns ...
* Superstition#Superstition and psychology * Taboo food and drink * Vegetarianism and religion *
Weight loss Weight loss, in the context of medicine, health, or physical fitness, refers to a reduction of the total body mass, by a mean loss of fluid, body fat (adipose tissue), or lean mass (namely bone mineral deposits, muscle, tendon, and other co ...


References


Further reading

*
Francis Gano Benedict Francis Gano Benedict (October 3, 1870 – April 14, 1957) was an American chemist, physiologist, and nutritionist who developed a calorimeter and a spirometer used to determine oxygen consumption and measure metabolic rate. Biography Born in Mi ...
. (1915)
''A Study of Prolonged Fasting''
Carnegie Institution of Washington. * *
Joan Jacobs Brumberg Joan Jacobs Brumberg (born April 29, 1944) is an American social historian and writes and lectures in the fields of women's history and medical history. Her first appointment at Cornell University (1979) was in Women's Studies and Human Development ...
. (1988). ''Fasting Girls: The Emergence of Anorexia Nervosa As a Modern Disease''. Harvard University Press. *
Caroline Walker Bynum Caroline Walker Bynum, FBA (born May 10, 1941, in Atlanta, Georgia)Caroline Walker Bynum short CV
at < ...
. (1987). ''Holy Feast and Holy Fast: The Religious Significance of Food to Medieval Women''. University of California Press. * John Arthur Glaze. (1928). ''Psychological Effects of Fasting''. ''
American Journal of Psychology The ''American Journal of Psychology'' is a journal devoted primarily to experimental psychology. It is the first such journal to be published in the English language (though ''Mind'', founded in 1876, published some experimental psychology ear ...
'' 40 (2): 236–253. * A. M. Johnstone. (2007)
''Fasting – the ultimate diet?''
''
Obesity Reviews ''Obesity Reviews'' is a monthly peer-reviewed medical journal, established in 2000, which publishes reviews on all obesity-related disciplines. It is the official journal of the World Obesity Federation and published on their behalf by Wiley-Blac ...
'' 8 (3): 211–222. * Walter Vandereycken, Ron Van Deth. (2001). ''From Fasting Saints to Anorexic Girls: The History of Self-Starvation''. Bloomsbury Academic.


External links

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