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{{Short description|Willing abstinence from, or reduced consumption of, food and/or drink}}
{{Use dmy dates|date=January 2019}}[[File:Fasting 4-Fasting-a-glass-of-water-on-an-empty-plate.jpg|thumb|A glass of water on an empty plate]]'''Fasting''' is the act of refraining from [[eating]], and sometimes [[drinking]]. However, from a purely [[physiology|physiological]] context, "fasting" may refer to the [[metabolism|metabolic]] status of a person who has not eaten overnight (before "[[breakfast]]"), or to the metabolic state achieved after complete [[digestion]] and [[Nutrient|absorption]] of a meal.<ref>{{Cite web|title=fasting {{!}} Definition, Description, Types, Benefits, & Facts|url=https://www.britannica.com/topic/fasting|access-date=2021-10-28|website=Encyclopedia Britannica|language=en}}</ref> Metabolic changes in the fasting state begin after absorption of a meal (typically 3–5 hours after eating).

A ''[[diagnostic fast]]'' is a prolonged fast, from 1–100 hours long (depending on age), conducted under observation, to facilitate the investigation of a health complication (usually [[hypoglycemia]]). Many people may also fast as part of a [[medical procedure]] or a [[check-up]], such as preceding a [[colonoscopy]] or [[surgery]], or before certain medical tests. ''[[Intermittent fasting]]'' is a technique sometimes used for [[weight loss]] or other health benefits that incorporates regular fasting into a person's [[dietary]] schedule. Fasting may also be part of a [[#Religious views|religious ritual]], often associated with specific scheduled fast days, as [[#Religious views|determined by the religion]], or be applied as a [[public demonstration]] for a given cause, in a practice known as a ''[[hunger strike]]''.

== Health effects ==
{{See also|Starvation response|Intermittent fasting|Autophagy|Fasting and longevity}}

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 [[Circulatory system#Cardiovascular system|cardiovascular]] and metabolic [[biomarker]]s similarly to a [[calorie restriction diet]] in people who are [[overweight]], obese or have [[metabolic syndrome]].<ref name="Cioffi2018">{{cite journal | vauthors = Cioffi I, Evangelista A, Ponzo V, Ciccone G, Soldati L, Santarpia L, Contaldo F, Pasanisi F, Ghigo E, Bo S | display-authors = 6 | title = Intermittent versus continuous energy restriction on weight loss and cardiometabolic outcomes: a systematic review and meta-analysis of randomized controlled trials | journal = Journal of Translational Medicine | volume = 16 | issue = 1 | article-number = 371 | date = December 2018 | pmid = 30583725 | pmc = 6304782 | doi = 10.1186/s12967-018-1748-4 | type = Systematic review | doi-access = free }}</ref><ref name="harris">{{cite journal | vauthors = Harris L, Hamilton S, Azevedo LB, Olajide J, De Brún C, Waller G, Whittaker V, Sharp T, Lean M, Hankey C, Ells L | display-authors = 6 | title = Intermittent fasting interventions for treatment of overweight and obesity in adults: a systematic review and meta-analysis | journal = JBI Database of Systematic Reviews and Implementation Reports | volume = 16 | issue = 2 | pages = 507–547 | date = February 2018 | pmid = 29419624 | doi = 10.11124/JBISRIR-2016-003248 | url = https://research.tees.ac.uk/ws/files/6438175/621636.pdf | access-date = 23 October 2019 | url-status = live | s2cid = 46780578 | archive-url = https://web.archive.org/web/20191030172956/https://research.tees.ac.uk/ws/files/6438175/621636.pdf | archive-date = 30 October 2019 }}</ref><ref name="mattson17">{{cite journal | vauthors = Mattson MP, Longo VD, Harvie M | title = Impact of intermittent fasting on health and disease processes | journal = Ageing Research Reviews | volume = 39 | pages = 46–58 | date = October 2017 | pmid = 27810402 | pmc = 5411330 | doi = 10.1016/j.arr.2016.10.005 }}</ref><ref name="Papamichou2019">{{cite journal | vauthors = Papamichou D, Panagiotakos DB, Itsiopoulos C | title = Dietary patterns and management of type 2 diabetes: A systematic review of randomised clinical trials | journal = Nutrition, Metabolism, and Cardiovascular Diseases | volume = 29 | issue = 6 | pages = 531–543 | date = June 2019 | pmid = 30952576 | doi = 10.1016/j.numecd.2019.02.004 | s2cid = 86497236 | type = Systematic review }}</ref>

A 2021 review found that moderate alternate-day fasting for two to six months was associated with reductions of body weight, [[body mass index]], and cardiometabolic [[Risk factor (epidemiology)|risk factor]]s in overweight or obese adults.<ref name="patikorn">{{Cite journal|last1=Patikorn|first1=Chanthawat|last2=Roubal|first2=Kiera|last3=Veettil|first3=Sajesh K.|last4=Chandran|first4=Viji|last5=Pham|first5=Tuan|last6=Lee|first6=Yeong Yeh|last7=Giovannucci|first7=Edward L.|last8=Varady|first8=Krista A.|last9=Chaiyakunapruk|first9=Nathorn|date=17 December 2021|title=Intermittent fasting and obesity-related health outcomes: An umbrella review of meta-analyses of randomized clinical trials|journal=JAMA Network Open|volume=4|issue=12|pages=e2139558|doi=10.1001/jamanetworkopen.2021.39558|pmid=34919135|pmc=8683964|issn=2574-3805}}</ref>

=== Medical application ===
{{See also|Preoperative fasting|Body cleansing|Nothing by mouth}}
Fasting is almost always practiced 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]]).<ref>{{Cite web |url=https://abcnews.go.com/Health/WomensHealth/story?id=7161746&page=1 |title=Do You Need to Starve Before Surgery?  |date=25 March 2009 |publisher=Abcnews.go.com |url-status=live |archive-url=https://web.archive.org/web/20110208095908/https://abcnews.go.com/Health/WomensHealth/story?id=7161746&page=1 |archive-date=8 February 2011 |access-date=18 October 2010}}</ref><ref>{{Cite web |url=http://www.abc.net.au/health/minutes/stories/2004/06/17/1137544.htm |title=Fasting before surgery – Health & Wellbeing |last=Norman |first=Dr |date=17 April 2003 |publisher=Abc.net.au |url-status=live |archive-url=https://web.archive.org/web/20100529211055/http://www.abc.net.au/health/minutes/stories/2004/06/17/1137544.htm |archive-date=29 May 2010 |access-date=18 October 2010}}</ref><ref>{{Cite web |url=http://www.yestheyrefake.net/anesthesia_full.htm |title=Anesthesia Information (full edition) &#124; From Yes They're Fake! |date=1 January 1994 |publisher=Yestheyrefake.net |archive-url=https://web.archive.org/web/20101112015650/http://www.yestheyrefake.net/anesthesia_full.htm |archive-date=12 November 2010 |access-date=18 October 2010}}</ref> Additionally, certain medical tests, such as [[cholesterol]] testing ([[lipid panel]]) or certain [[blood glucose]] measurements require fasting for several hours so that a [[baseline (medicine)|baseline]] can be established.

=== Mental health ===
In one review, fasting improved [[alertness]], [[depression (mood)|mood]], and subjective feelings of well-being, possibly improving overall symptoms of [[Depression (mood)|depression]], and boosting cognitive performance.<ref>{{Cite journal |last1=Fond |first1=G |last2=MacGregor |first2=A |last3=Leboyer |first3=M |last4=Michalsen |first4=A |year=2013 |title=Fasting in mood disorders: Neurobiology and effectiveness. A review of the literature |url=http://www.hal.inserm.fr/inserm-00789122/document |url-status=live |journal=Psychiatry Research |volume=209 |issue=3 |pages=253–258 |doi=10.1016/j.psychres.2012.12.018 |pmid=23332541 |s2cid=39700065 |archive-url=https://web.archive.org/web/20180617165447/http://www.hal.inserm.fr/inserm-00789122/document |archive-date=17 June 2018 |access-date=4 November 2018}}</ref>

=== Weight loss ===

==== Intermittent fasting ====
{{Main|Intermittent fasting}}
There is little evidence to suggest that intermittent fasting for periods shorter than 24 hours is effective for sustained [[weight loss]] in obese adults.<ref name="unders">{{Cite book |last1=Whitney |first1=Eleanor Noss |url=https://books.google.com/books?id=Mib1CAAAQBAJ&pg=SA7-PA21 |title=Understanding Nutrition |last2=Rolfes |first2=Sharon Rady |date=2012 |publisher=Cengage Learning |isbn=978-1-133-58752-1 |language=en |access-date=22 January 2017 |archive-url=https://web.archive.org/web/20170202031451/https://books.google.de/books?id=Mib1CAAAQBAJ&pg=SA7-PA21 |archive-date=2 February 2017 |url-status=live}}</ref><ref>{{Cite journal |last1=Anton |first1=Stephen D |last2=Moehl |first2=Keelin |last3=Donahoo |first3=William T |last4=Marosi |first4=Krisztina |last5=Lee |first5=Stephanie A |last6=Mainous |first6=Arch G |last7=Leeuwenburgh |first7=Christiaan |last8=Mattson |first8=Mark P|display-authors=3 |year=2017 |title=Flipping the Metabolic Switch: Understanding and Applying the Health Benefits of Fasting |journal=Obesity |volume=26 |issue=2 |pages=254–268 |doi=10.1002/oby.22065 |pmc=5783752 |pmid=29086496}}</ref>

==== Prolonged fasting ====

Prolonged fasting (also called extended fasting or water fasting) involves periods of fasting above 24 hours, typically in the range of 5–20 days.<ref name=":2">{{Cite journal |last1=Ezpeleta |first1=Mark |last2=Cienfuegos |first2=Sofia |last3=Lin |first3=Shuhao |last4=Pavlou |first4=Vasiliki |last5=Gabel |first5=Kelsey |last6=Varady |first6=Krista A. |date=2024-04-12 |title=Efficacy and safety of prolonged water fasting: a narrative review of human trials |journal=Nutrition Reviews |volume=82 |issue=5 |pages=664–675 |doi=10.1093/nutrit/nuad081 |issn=1753-4887 |pmid=37377031|pmc=11494232 }}</ref> In early fasting, the body operates under a relatively high level of [[gluconeogenesis]], though this eventually decreases as the body's metabolism switches into [[ketosis]], causing [[ketones]] to replace [[glucose]] as the primary energy source in the [[central nervous system]].<ref name=":1">{{Cite journal |last1=Kerndt |first1=Peter R. |last2=Naughton |first2=James L. |last3=Driscoll |first3=Charles E. |last4=Loxterkamp |first4=David A. |date=November 1982 |title=Fasting: The History, Pathophysiology and Complications |journal=Western Journal of Medicine |volume=137 |issue=5 |pages=379–399 |issn=0093-0415 |pmc=1274154 |pmid=6758355}}</ref> As prolonged fasting continues, drastic decreases in [[sodium]], [[potassium]], [[magnesium]], and other [[minerals]] are noted, which can lead to [[hyponatremia]].<ref name=":1" /> In some diet systems, these losses are offset with non-caloric [[electrolyte]] supplements, such as electrolyte beverages.<ref>{{Cite web |title=Snake Diet—What It Is and Why It's Dangerous |url=https://www.health.com/weight-loss/what-is-snake-diet |access-date=2024-09-29 |website=Health |language=en}}</ref> Typical observed weight loss under prolonged fasting averages at 0.9&nbsp;kg per day during the first week and 0.3&nbsp;kg per day by the third week.<ref name=":1" /> In early fasting, during periods of high gluconeogenesis, roughly two-thirds of weight lost is lean muscle mass as opposed to fat.<ref name=":2" /><ref name=":3">{{Cite journal |last=Cahill |first=G. F. |date=1983 |title=President's address. Starvation. |journal=Transactions of the American Clinical and Climatological Association |volume=94 |pages=1–21 |issn=0065-7778 |pmc=2279566 |pmid=6764569}}</ref> After the gluconeogenic phase, however, the ratio of body fat lost to lean tissue lost becomes roughly 7:6.<ref name=":3" />

===Longevity===

There is no [[evidence-based medicine|sound clinical evidence]] that fasting can promote [[longevity]] in humans.<ref name="lee">{{cite journal |vauthors=Lee MB, Hill CM, Bitto A, Kaeberlein M |title=Antiaging diets: Separating fact from fiction |journal=Science |volume=374 |issue=6570 |article-number=eabe7365 |date=November 2021 |pmid=34793210 |pmc=8841109 |doi=10.1126/science.abe7365}}</ref>

==Adverse effects==
===Refeeding syndrome===
{{main|Refeeding syndrome}}

[[Refeeding syndrome]] is a [[metabolic]] disturbance which occurs as a result of reinstitution of nutrition in people and animals who are [[starvation|starved]], severely [[malnourishment|malnourished]], or metabolically stressed because of severe illness. When too much food or liquid nutrition supplement is eaten during the initial four to seven days following a [[malnutrition]] event, the production of [[glycogen]], [[fat]] and [[protein]] in cells may cause low [[serum (blood)|serum]] concentrations of [[Hypokalemia|potassium]], [[Magnesium deficiency|magnesium]] and [[Hypophosphatemia|phosphate]].<ref name=pmid18583681>{{cite journal |vauthors=Mehanna HM, Moledina J, Travis J |title=Refeeding syndrome: what it is, and how to prevent and treat it |journal=BMJ |volume=336 |issue=7659 |pages=1495–8 |date=June 2008 |pmid=18583681 |pmc=2440847 |doi=10.1136/bmj.a301 }}</ref><ref name=":0">{{Cite journal|last1=Doig|first1=GS|last2=Simpson|first2=F|last3=Heighes|last4=Bellomo|first4=R|last5=Chesher|first5=D|last6=Caterson|first6=ID|last7=Reade|first7=MC|last8=Harrigan|first8=PWJ|date=2015-12-01|title=Restricted versus continued standard caloric intake during the management of refeeding syndrome in critically ill adults: a randomised, parallel-group, multicentre, single-blind controlled trial|journal=The Lancet Respiratory Medicine|volume=3|issue=12|pages=943–952|doi=10.1016/S2213-2600(15)00418-X|issn=2213-2619|pmid=26597128}}</ref> The [[electrolyte imbalance]] may cause neurologic, pulmonary, cardiac, neuromuscular, and hematologic symptoms—many of which, if severe enough, may result in death.

Refeeding syndrome can occur when someone does not eat for several days at a time usually beginning after 4–5 days with no food.<ref>{{cite journal |vauthors=Webb GJ, Smith K, Thursby-Pelham F, Smith T, Stroud MA, Da Silva AN |title=Complications of emergency refeeding in anorexia nervosa: case series and review |journal=Acute Medicine |volume=10 |issue=2 |pages=69–76 |year=2011 |doi=10.52964/AMJA.0470 |pmid=22041604 |doi-access=free }}</ref>

===Gallstones===
{{main|Gallstone}}

Fasting can increase the risk of developing gallstones for some people. This is thought to occur due to decreased gallbladder movement with no food to be digested, which can cause the bile to become over-concentrated with cholesterol, combined with the liver secreting extra cholesterol into bile as the body metabolizes fat during rapid weight loss, further exacerbating the situation.<ref>{{Cite web |title=Dietary advice for patients with gallstones |url=https://www.cuh.nhs.uk/patient-information/dietary-advice-for-patients-with-gallstones/ |access-date=2024-08-23 |website=Cambridge University Hospitals |language=en-GB}}</ref>

== 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]] 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.<ref name="Garcia, M. 2007 p. 103">Garcia, M. (2007) ''The Gospel of Cesar Chavez: My Faith in Action'' Sheed & Ward Publishing p. 103</ref>

The political leader [[Gandhi]] undertook several long fasts as political and social protests. Gandhi's fasts had a significant impact on the [[British Raj]] and the [[Indian subcontinent|Indian]] population generally.<ref>{{Cite journal|last=Harinarayanan|first=A.|date=1986|title=GANDHI'S FASTS: AN ANALYSIS (Summary)|journal=Proceedings of the Indian History Congress|volume=47|pages=696–698|jstor=44141630|issn=2249-1937}}</ref>

In Northern Ireland in 1981, a prisoner, [[Bobby Sands]], was part of the [[1981 Irish hunger strike]], protesting for better rights in prison.<ref>[https://news.bbc.co.uk/onthisday/hi/dates/stories/july/18/newsid_2514000/2514727.stm ON THIS DAY 1981: Violence erupts at Irish hunger strike protest] , ''[[BBC News]]''</ref> 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.

The American civil rights activist [[César Chávez]] 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.<ref name="Garcia, M. 2007 p. 103" /><ref name="Shaw, R. 2008 p.92">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</ref> Chávez regarded a spiritual fast as "a personal spiritual transformation".<ref>Espinosa, G. Garcia, M ''Mexican American Religions:Spirituality activism and culture''(2008) Duke University Press, p 108</ref> Other progressive campaigns have adopted the tactic.<ref>Shaw, R. (2008)''Beyond the Fields: Cesar Chavez, the UFW, and the struggle for justice in the 21st century'' University of California Press, p.93</ref>

== Religious views ==
{{Main|Fasting in religion}}
Fasting is practiced in various religions, and details of fasting practices differ.

[[Yom Kippur]], [[Tisha B'av]], [[Fast of Esther]], [[Fast of Gedalia|Tzom Gedalia]], the [[Seventeenth of Tammuz|Seventeenth of Tamuz]], the [[Tenth of Tevet]], and [[Fast of the Firstborn]] are examples of fasting in [[Judaism]].<ref>{{cite web |url=http://www.al-mawrid.org/pages/articles_english_detail.php?rid=196&cid=330&search=fasting |title=History of the Fast |access-date=2016-02-14 |archive-url=https://web.archive.org/web/20141227090756/http://www.al-mawrid.org/pages/articles_english_detail.php?rid=196&cid=330&search=fasting |archive-date=27 December 2014}}</ref> Yom Kippur and Tisha B'Av are 25-hour fasts in which observers abstain from consuming any food or liquid from sunset until nightfall the next day and include other restrictions. The fasts of Esther, Gedalia, Tamuz, and Tevet all last from dawn until nightfall and therefore length varies depending on the time of the year. The Fast of the Firstborn is not biblically mandated and can therefore be ended early in the case of a [[seudat mitzvah]].

[[Lent]] is a common period of fasting in [[Christianity]]. In the Catholic Church, the current practice of fast and abstinence is regulated by Canons 1250–1253 of the 1983 code.<ref>{{cite web |url=https://www.vatican.va/archive/ENG1104/__P4O.HTM |title=1983 Code of Canon Law |publisher=[[The Holy See]] |access-date=2011-11-19 |archive-url=https://web.archive.org/web/20111115004422/https://www.vatican.va/archive/ENG1104/__P4O.HTM |archive-date=2011-11-15 }}</ref>  They specify that all Fridays throughout the year, and the time of Lent are penitential times throughout the entire Church. All persons who have completed their fourteenth year are bound by the law of abstinence on all Fridays unless they are solemnities, and again on Ash Wednesday  and Good Friday. Fasting must be observed by those who have attained their majority, until the beginning of their sixtieth year. The precept to both fast and abstinence must be observed on [[Ash Wednesday]] and [[Good Friday]]. Certain communities of [[Lutheranism|Lutheran Churches]] advocate fasting during designated times such as Lent,<ref name="GassmannOldenburg2011">{{cite book|last1=Gassmann|first1=Günther|last2=Oldenburg|first2=Mark W.|title=Historical Dictionary of Lutheranism|date=10 October 2011|publisher=Scarecrow Press|language=en|isbn=978-0-8108-7482-4|page=229|quote=In many Lutheran churches, the Sundays during the Lenten season are called by the first word of their respective Latin Introitus (with the exception of Palm/Passion Sunday): Invocavit, Reminiscere, Oculi, Laetare, and Judica. Many Lutheran church orders of the 16th century retained the observation of the Lenten fast, and Lutherans have observed this season with a serene, earnest attitude. Special days of eucharistic communion were set aside on Maundy Thursday and Good Friday.}}</ref><ref>[http://www.lcms.org/pages/wPage.asp?ContentID=246&IssueID=19 What is the holiest season of the Church Year?] {{webarchive|url=https://web.archive.org/web/20090209190015/http://www.lcms.org/pages/wPage.asp?ContentID=246&IssueID=19 |date=9 February 2009 }}. Retrieved 3 February 2010. [https://web.archive.org/web/20090209190015/http://www.lcms.org/pages/wPage.asp?ContentID=246&IssueID=19 Archived copy] at the [[Internet Archive]]</ref> especially on Ash Wednesday and Good Friday.<ref name="GassmannOldenburg2011" /><ref name="Pfatteicher1990">{{cite book|last=Pfatteicher|first=Philip H.|title=Commentary on the Lutheran Book of Worship: Lutheran Liturgy in Its Ecumenical Context|year=1990|publisher=Augsburg Fortress Publishers|language=en |isbn=978-0-8006-0392-2|pages=223–244, 260|quote=The Good Friday fast became the principal fast in the calendar, and even after the Reformation in Germany many Lutherans who observed no other fast scrupulously kept Good Friday with strict fasting.}}</ref><ref name="JacobsHaas1899">{{cite book|last1=Jacobs|first1=Henry Eyster|last2=Haas|first2=John Augustus William|title=The Lutheran Cyclopedia|url=https://archive.org/details/cu31924029466533|year=1899|publisher=Scribner|language=en|page=[https://archive.org/details/cu31924029466533/page/n121 110]|quote=By many Lutherans Good Friday is observed as a strict fast. The lessons on Ash Wednesday emphasize the proper idea of the fast. The Sundays in Lent receive their names from the first words of their Introits in the Latin service, Invocavit, Reminiscere, Oculi, Lcetare, Judica.|access-date=14 November 2019|archive-url=https://web.archive.org/web/20100409170648/http://www.archive.org/details/cu31924029466533|archive-date=9 April 2010|url-status=live}}</ref> The [[rogation days]] are traditional days of fasting, as well as abstinence of meat, in Lutheranism.<ref>{{cite web |title=Fasting Guidelines |url=https://www.glctulsa.org/wp-content/uploads/2016/02/Fasting-Guidelines-Rev-2016.pdf |publisher=Grace Evangelical Lutheran Church |access-date=5 July 2025 |archive-url=https://web.archive.org/web/20200630235736/https://www.glctulsa.org/wp-content/uploads/2016/02/Fasting-Guidelines-Rev-2016.pdf|archive-date=30 June 2020 |page=3}}</ref> ''A Handbook for the Discipline of Lent'' delineates the following Lutheran fasting guidelines:<ref name="ELCA1978" />
{{blockquote|
# Fast on Ash Wednesday and Good Friday with only one simple meal during the day, usually without meat.
# Refrain from eating meat (bloody foods) on all Fridays in Lent, substituting fish for example.
# Eliminate a food or food group for the entire season. Especially consider saving rich and fatty foods for Easter.
# Consider not eating before receiving Communion in Lent.
# Abstain from or limit a favorite activity (television, movies, etc.) for the entire season, and spend more time in prayer, Bible study, and reading devotional material.<ref name="ELCA1978">{{cite web|url=http://www.ststephenlutheranchurch.org/pdf/Disciplines%20of%20Lent-%20Handbook.pdf|title=A Handbook for the Discipline of Lent|last=Weitzel|first=Thomas L.|year=1978|publisher=Evangelical Lutheran Church in America|language=en|access-date=17 March 2018|archive-url=https://web.archive.org/web/20180317164940/http://www.ststephenlutheranchurch.org/pdf/Disciplines%20of%20Lent-%20Handbook.pdf|archive-date=17 March 2018|url-status=live}}</ref>}}

In addition to the fasts mentioned above, Catholics must also observe the Eucharistic Fast, which in the Latin Church involves taking nothing but water or medicine into the body for one hour before receiving the [[Eucharist]]{{1983CIC|919}}. In Lutheranism, the [[Luther's Small Catechism|Small Catechism]], with regard to the Eucharistic Fast, states: "Fasting and bodily preparation are indeed a fine outward training".<ref>{{cite web |author1=[[Martin Luther]] |title=The Small Catechism |url=https://els.org/wp-content/download/centennial/ELS-Small-Catechism-w-questions-2016-WEB.pdf |publisher=[[Evangelical Lutheran Synod]] |access-date=18 May 2025}}</ref><ref name="Preus2015">{{cite web |last1=Preus |first1=Klemet |title=Communion Every Sunday: Surprise, Surprise |url=https://steadfastlutherans.org/blog/2015/01/communion-every-sunday-surprise-surprise/ |access-date=18 May 2025 |date=8 January 2015}}</ref> Though voluntary in Lutheranism, the Eucharistic Fast is kept from midnight until the reception of the Eucharist. Theologically, the "Eucharistic Fast is always in anticipation for the Eucharistic Feast, a reminder of the Last Day when all poverty is abolished, the necessity of fasting has ceased and every prayer answered as all of God's people celebrate the marriage supper of the Lamb."<ref name="Ristau2020">{{cite web |last1=Ristau |first1=Harold |title=Tempted to fast? Fasting and feasting as the Body of Christ |url=https://www.lutheranmissionaustralia.org.au/news/tempted-to-fast-fasting-and-feasting-as-the-body-of-christ |publisher=Lutheran Mission Australia |access-date=18 May 2025 |language=en-AU |date=2020}}</ref>

[[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]]), after Easter (the [[Apostles' Fast]]) and in early August (the [[Dormition Fast]]).

Members of [[the Church of Jesus Christ of Latter-day Saints]] generally abstain from food and drink for two consecutive meals in a 24-hour period, on the first Sunday of each month, and members are invited to donate the money they would have used for those meals to assist others in need (called a [[fast offering]]).<ref name="ReferenceB">{{Cite web |title=The Law of the Fast |url=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 |access-date=7 October 2023 |website=[[The Church of Jesus Christ of Latter-day Saints]]}}</ref>

[[Muslims]] fast during the month of [[Ramadan]] each year. The fast includes refraining from consuming any food or liquid from dawn until sunset. It is a religious obligation for all Muslims unless they are children or are physically unable to fast.

Fasting is a feature of [[ascetic]] traditions in religions such as [[Hinduism]] and [[Buddhism]].

[[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".<ref>Brahma's Net Sutra, minor precept 30</ref>

Members of the [[Baháʼí Faith]] observe a [[Nineteen Day Fast]] from sunrise to sunset during March each year.

== In alternative medicine ==

Although practitioners of [[alternative medicine]] promote "[[Detoxification (alternative medicine)|cleansing the body]]" through fasting,<ref name=Hunger>{{cite book|last1=Russell|first1=Sharman Apt|last2=Russell|first2=Sharman|title=Hunger: An Unnatural History|publisher=Basic Books|isbn=978-0-7867-2239-6|url=https://books.google.com/books?id=XT2WzJuNPZ8C&pg=PT35|access-date=22 January 2017|language=en|date=1 August 2008|archive-url=https://web.archive.org/web/20170202031142/https://books.google.de/books?id=XT2WzJuNPZ8C&pg=PT35|archive-date=2 February 2017|url-status=live}}</ref> (as though it were a diagnostic fast) the concept of "detoxification" is a marketing myth with little scientific basis for its rationale or efficacy.<ref name=bda>{{cite web |url=https://www.bda.uk.com/foodfacts/detoxdiets.pdf |publisher=British Dietetic Association |title=Detox diets |date=May 2016 |last=Porter |first=Sian |quote=The whole idea of detox is nonsense. The body is a well-developed system that has its own built-in mechanisms to detoxify and remove waste and toxins. Our body constantly filters out, breaks down and excretes toxins and waste products like alcohol, medications, products of digestion, dead cells, chemicals from pollution and bacteria |access-date=29 January 2019 |archive-url=https://web.archive.org/web/20161017170537/https://www.bda.uk.com/foodfacts/detoxdiets.pdf |archive-date=17 October 2016 |url-status=live }}</ref><ref name="sbm2011">{{cite web | title=Fashionably toxic | author=David Gorski | website=Science-Based Medicine | date=23 May 2011 | url=https://sciencebasedmedicine.org/fashionable-toxins/ | access-date=29 January 2019 | archive-url=https://web.archive.org/web/20190130001710/https://sciencebasedmedicine.org/fashionable-toxins/ | archive-date=30 January 2019 | url-status=live }}</ref>

During the early 20th century, fasting was promoted by alternative health writers such as [[Hereward Carrington]], [[Edward H. Dewey]], [[Bernarr Macfadden]], [[Frank McCoy (author)|Frank McCoy]], [[Edward Earle Purinton]], [[Upton Sinclair]] and [[Wallace Wattles]].<ref name="Griffith 2000">Griffith, R. Marie. (2000). ''Apostles of Abstinence: Fasting and Masculinity during the Progressive Era''. ''[[American Quarterly]]'' 52 (4): 599-638.</ref> All of these writers were either involved in the [[Orthopathy|natural hygiene]] or [[New Thought]] movement.<ref name="Griffith 2000"/> [[Arnold Ehret]]'s pseudoscientific Mucusless Diet Healing System espoused fasting.<ref name="Kuske 1983">Kuske, Terrence T. (1983). [https://www.sciencedirect.com/science/article/pii/B9780723670469500205 ''Quackery and Fad Diets''] {{Webarchive|url=https://web.archive.org/web/20190420014820/https://www.sciencedirect.com/science/article/pii/B9780723670469500205 |date=20 April 2019 }}. In Elaine B. Feldman. ''Nutrition in the Middle and Later Years''. John Wright & Sons. pp. 291-303. {{ISBN|0-7236-7046-3}}</ref>

[[Linda Hazzard]], put her patients on such strict fasts that some of them died of [[starvation]]. She was responsible for the death of more than 40 patients under her care.<ref>Hall, Harriett. (2016). [https://sciencebasedmedicine.org/natural-medicine-starvation-and-murder-the-story-of-linda-hazzard/ "Natural Medicine, Starvation, and Murder: The Story of Linda Hazzard"] {{Webarchive|url=https://web.archive.org/web/20190601162549/https://sciencebasedmedicine.org/natural-medicine-starvation-and-murder-the-story-of-linda-hazzard/ |date=1 June 2019 }}. Science-Based Medicine. Retrieved 1 May 2019.</ref><ref>[https://www.medicalbag.com/home/features/despicable-doctors/linda-hazzard-the-starvation-doctor/ "Linda Hazzard: The "Starvation Doctor""] {{Webarchive|url=https://web.archive.org/web/20190601162549/https://www.medicalbag.com/home/features/despicable-doctors/linda-hazzard-the-starvation-doctor/ |date=1 June 2019 }}. Retrieved 1 May 2019.</ref>

In 1911, [[Upton Sinclair]] authored ''[[The Fasting Cure]]'', which made sensational claims of fasting curing practically all diseases, including [[cancer]] and [[syphilis]].<ref>Upton Sinclair, ''The Fasting Cure'' (New York: Mitchell Kennerley, 1911), p. 44.</ref> Sinclair states he recommended fasting for all diseases except [[tuberculosis]].<ref>Sinclair, ''The Fasting Cure'', p. 44.</ref> Sinclair has been described as "the most credulous of faddists. In 1932, physician [[Morris Fishbein]] listed fasting as a [[fad diet]] and commented that "prolonged fasting is never necessary and invariably does harm".<ref>Fishbein, Morris. (1932). [https://archive.org/details/1932FishbeinFadsAndQuackeryInHealing/page/n261 ''Fads and Quackery in Healing: An Analysis of the Foibles of the Healing Cults'']. New York: Covici Friede. p. 253</ref>

== Types of fasting ==

=== Type by religion ===
{{Main|Religious fasting}}

* [[Lent]]
* [[Great Lent]]
* [[Tenth of Tevet]]
* [[Seventeenth of Tamuz]]
* [[Fast of Gedalia]]
* [[Vrata]]
* [[Fast of Esther]]
* [[Tisha B'Av]]
* [[Yom Kippur]]
* [[Fast of the Firstborn]]
* [[Ramadan]]
* [[Nativity Fast]]
* [[Apostles Fast]]
* [[Dormition Fast]]
* [[Fasting in Buddhism]]
* [[Nineteen Day Fast]]
* [[Daniel Fast]]
* [[Black Fast]]
* [[Fasting in Jainism]]

=== Type by method ===

* Electrolyte supplemented water fasting
* Dry fasting
* [[Juice fasting]]
* Water fasting

=== Type by schedule ===
Source:<ref>{{Cite web |title=Intermittent Fasting: How It Works |url=https://health.clevelandclinic.org/intermittent-fasting-4-different-types-explained |access-date=2024-08-23 |website=Cleveland Clinic |language=en}}</ref>

* Alternate day
* Eat: stop: eat
* [[Intermittent fasting]]
* One Meal A Day (OMAD)/Warrior diet
* Prolonged fasting
* The 16/8 or 14/10 
* The 40-days and 40-nights 
* The 5:2

=== Type by motivation ===

* [[Autophagy]]
* [[Avoidant/restrictive food intake disorder]]
* [[Calorie restriction]]
* [[Drunkorexia]]
* [[Hunger strike]]
* [[Inedia]]
* [[Insulin resistance]] management
* [[Fasting and longevity|Longevity]]
* [[Sallekhana]]
* [[Weight loss]]

== See also ==
{{Portal|Science|Medicine|Food|Religion}}
<!-- Please keep entries in alphabetical order & add a short description [[WP:SEEALSO]] -->
{{div col|colwidth=20em}}
* [[Asceticism]]
* [[Autophagy]]
* [[Black Fast]]
* [[Calorie restriction]]
* [[Fasting and longevity]]
* [[Fasting in Jainism]]
* [[Force-feeding]]
* [[Inedia]]
* [[Santhara]]
* [[Weight loss]]
{{div col end}}
<!-- please keep entries in alphabetical order -->

== References ==
{{Reflist|2}}

== Sources ==
* {{Citation | orig-date = 1983 | publisher = Libreria Editrice Vaticana | date = 4 November 2003 | url = https://www.vatican.va/archive/ENG1104/_INDEX.HTM | title = Code of Canon Law ''(CIC)'' | place = Rome | ref = {{SfnRef | CIC| 1983}}}}.

== Further reading ==
* [[Francis Gano Benedict]]. (1915). [https://archive.org/details/studyofprolonged00beneuoft/page/n6 ''A Study of Prolonged Fasting'']. Carnegie Institution of Washington.
*{{cite book|chapter=[[s:The Sermon on the Mount (Bossuet)/Day 28|Day 28: Of Fasting]]|title=The Sermon on the Mount|year=1900|publisher=Longmans, Green, and Co.|first=Jacques-Bénigne|last=Bossuet|author-link=Jacques-Bénigne Bossuet}}
* [[Joan Jacobs Brumberg]]. (1988). ''Fasting Girls: The Emergence of Anorexia Nervosa As a Modern Disease''. Harvard University Press.
* [[Caroline Walker Bynum]]. (1987). ''Holy Feast and Holy Fast: The Religious Significance of Food to Medieval Women''. University of California Press. {{ISBN|978-0-520-06329-7}}
* John Arthur Glaze. (1928). ''Psychological Effects of Fasting''. ''[[American Journal of Psychology]]'' 40 (2): 236–253.
* A. M. Johnstone. (2007). [https://onlinelibrary.wiley.com/doi/full/10.1111/j.1467-789X.2006.00266.x ''Fasting – the ultimate diet?'']. ''[[Obesity Reviews]]'' 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 ==
{{Commons category}}
{{Wikiquote}}
* {{Cite EB1911 |wstitle=Fasting |volume=10 |pages=193–198 |short=x}}
* {{Cite NIE |wstitle=Fast |year=1905 |short=x}}
* {{Cite CE1913 |last=O'Neill |first=James David |wstitle=Fast  |volume=5 |short=x}}

{{Christianity footer}}
{{Jews and Judaism}}
{{Islam topics|state=collapsed}}
{{Buddhism topics}}
{{Fad diets}}
{{Naturopathy}}
{{Simple living}}
{{Authority control}}

[[Category:Fasting| ]]
[[Category:Asceticism]]
[[Category:Biologically based therapies]]
[[Category:Diets]]
[[Category:Eating behaviors]]
[[Category:Fad diets]]
[[Category:Naturopathy]]
[[Category:Religious food and drink]]