Fasting

== 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 | pages = 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]]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|url=https://doi.org/10.1001/jamanetworkopen.2021.39558|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 |url-status=dead |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 ===
{{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=978-1133587521 |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>

===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 |pages=eabe7365 |date=November 2021 |pmid=34793210 |pmc=8841109 |doi=10.1126/science.abe7365}}</ref>