intermittent fasting

Fasting is an ancient tradition, having been practiced by many cultures and religions over centuries.{{Cite web |url=https://idmprogram.com/fasting-a-history-part-i/ |title=Fasting - A History | vauthors = Fung J |date=11 April 2015 |website=Intensive Dietary Management |access-date=4 October 2019 |archive-url=https://web.archive.org/web/20191105041441/https://idmprogram.com/fasting-a-history-part-i/ |archive-date=5 November 2019 |url-status=live }}{{Cite news | vauthors = Hicks C |url=https://www.telegraph.co.uk/lifestyle/11524808/The-history-of-fasting.html |title=Why fasting is now back in fashion |date=13 April 2015 |work=The Telegraph |access-date=14 January 2019 |archive-url=https://web.archive.org/web/20190116115505/https://www.telegraph.co.uk/lifestyle/11524808/The-history-of-fasting.html |archive-date=16 January 2019 |url-status=live }}

Therapeutic intermittent fasts for the treatment of obesity have been investigated since at least 1915, with a renewed interest in the medical community in the 1960s after Bloom and his colleagues published an "enthusiastic report".{{Cite book | vauthors = Howard AN |title=Obesity: Its Pathogenesis and Management |date=1975 |publisher=Springer Netherlands |isbn=978-94-011-7155-7 |pages=123–153 |chapter=Dietary Treatment of Obesity |type=Monograph |doi=10.1007/978-94-011-7155-7_5}}{{rp|125}} Intermittent fasts, or "short-term starvation periods", ranged from 1 to 14 days in these early studies.{{cite journal | vauthors = Duncan GG | title = The Control of Obesity by Intermittent Fasts | journal = Transactions of the American Clinical and Climatological Association | volume = 74 | issue = 5 | pages = 121–9 | date = September 1964 | pmid = 14047310 | pmc = 2249073 | doi = 10.1016/S0025-7125(16)33406-X | type = Review }} This enthusiasm penetrated lay magazines, which prompted researchers and clinicians to caution about the use of intermittent fasts without medical monitoring.{{cite journal | vauthors = Dinning JS | title = Correction of Obesity by Fasting | journal = Nutrition Reviews | volume = 21 | issue = 10 | pages = 304–6 | date = October 1963 | pmid = 14069065 | doi = 10.1111/j.1753-4887.1963.tb07474.x | type = Mini-review }}

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There are multiple methods of intermittent fasting.{{cite journal | vauthors = Tinsley GM, La Bounty PM | title = Effects of intermittent fasting on body composition and clinical health markers in humans | journal = Nutrition Reviews | volume = 73 | issue = 10 | pages = 661–74 | date = October 2015 | pmid = 26374764 | doi = 10.1093/nutrit/nuv041 }}{{Cite web |url=https://www.hsph.harvard.edu/nutritionsource/healthy-weight/diet-reviews/intermittent-fasting/ |title=Diet Review: Intermittent Fasting for Weight Loss |date=16 January 2018 |website=The Nutrition Source |publisher=Harvard School of Public Health |access-date=4 October 2019 |archive-url=https://web.archive.org/web/20191011210453/https://www.hsph.harvard.edu/nutritionsource/healthy-weight/diet-reviews/intermittent-fasting/ |archive-date=11 October 2019 |url-status=live }}{{Cite journal |last1=Varady |first1=Krista A. |last2=Cienfuegos |first2=Sofia |last3=Ezpeleta |first3=Mark |last4=Gabel |first4=Kelsey |date=11 October 2021 |title=Cardiometabolic Benefits of Intermittent Fasting |url=https://www.annualreviews.org/doi/10.1146/annurev-nutr-052020-041327 |journal=Annual Review of Nutrition |language=en |volume=41 |issue=1 |pages=333–361 |doi=10.1146/annurev-nutr-052020-041327 |pmid=34633860 |s2cid=238636406 |issn=0199-9885}}

• Time-restricted eating involves eating only during a certain number of hours each day, often establishing a consistent daily pattern of caloric intake within an 8–12-hour time window. This schedule may align food intake with circadian rhythms (establishing eating windows that begin after sunrise and end around sunset).{{cite journal |last1=Chaix |first1=Amandine |last2=Manoogian |first2=Emily N.C. |last3=Melkani |first3=Girish C. |last4=Panda |first4=Satchidananda |title=Time-Restricted Eating to Prevent and Manage Chronic Metabolic Diseases |journal=Annual Review of Nutrition |date=21 August 2019 |volume=39 |issue=1 |pages=291–315 |doi=10.1146/annurev-nutr-082018-124320 |pmid=31180809 |pmc=6703924 }}{{Cite journal |last1=Parr |first1=Evelyn B |last2=Devlin |first2=Brooke L |last3=Hawley |first3=John A |date=2022-05-01 |title=Perspective: Time-Restricted Eating—Integrating the What with the When |journal=Advances in Nutrition |language=en |volume=13 |issue=3 |pages=699–711 |doi=10.1093/advances/nmac015 |issn=2161-8313 |pmc=9156382 |pmid=35170718}}
• One meal a day fasting is having just one meal a day, and not having anything for the rest of the day.
• Alternate-day fasting involves 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. There are two subtypes:{{cite journal | vauthors = Patterson RE, Sears DD | title = Metabolic Effects of Intermittent Fasting | journal = Annual Review of Nutrition | volume = 37 | issue = 1 | pages = 371–393 | date = August 2017 | pmid = 28715993 | doi = 10.1146/annurev-nutr-071816-064634 | s2cid = 4612540 }}
• Complete alternate-day fasting is total intermittent energy restriction (IER vs. CER = continuous energy restriction), where no calories are consumed on fasting days.
• Modified alternate-day fasting involves partial intermittent energy restriction which allows the consumption of up to 25% of daily calorie needs on fasting days instead of complete fasting. This is akin to alternating days with normal eating and days with a very-low-calorie diet.{{cite journal | vauthors = Johnstone A | title = Fasting for weight loss: an effective strategy or latest dieting trend? | journal = International Journal of Obesity | volume = 39 | issue = 5 | pages = 727–33 | date = May 2015 | pmid = 25540982 | doi = 10.1038/ijo.2014.214 | type = Review | s2cid = 24033290 }}
• 5:2 diet is a type of periodic fasting (that does not follow a particular food pattern) which focuses entirely on calorie content. In other words, two days of the week are devoted to consumption of approximately 500 to 600 calories, or about 25% of regular daily caloric intake, with normal calorie intake during the other five days of the week. It was first documented in a 2011 article co-authored by Michelle Harvie, Mark Mattson, and 14 additional scientists.{{cite journal |last1=Harvie |first1=Michelle |author-link1= |last2=Pegington |first2=Mary |author-link2= |last3=Mattson |first3=Mark |author-link3=Mark Mattson |last4=Frystyk |first4=Jan |author-link4= |last5=Dillon |first5=Bernice |year=2011 |title=The effects of intermittent or continuous energy restriction on weight loss and metabolic disease risk markers: a randomised trial in young overweight women |journal=International Journal of Obesity|volume=35 |issue=5 |pages=714–727|doi=10.1038/ijo.2010.171 |pmid=20921964 |pmc=3017674 }}{{cite book|last=Mattson|first=Mark|date=2022|title=The Intermittent Fasting Revolution: The Science of Optimizing Health and Enhancing Performance|location=Boston|publisher=MIT Press|page= 198 (Kindle edition)|isbn=978-0-262-54598-3}} It was later published in the UK and Australia by Michael Mosley through the 2012 BBC documentary Eat, Fast and Live Longer (where he learned about the 5:2 diet from Mark Mattson).{{Cite news|url=https://www.theguardian.com/society/2016/may/22/michael-mosley-ecigarettes-miracle-menace-tv|title=Michael Mosley: 'No male in my family has made it beyond 72'|first=Carole|last=Cadwalladr|newspaper=The Observer |date=22 May 2016|via=The Guardian}} It also became common in Australia.{{Cite web |url=https://www.bbc.com/news/health-19112549 |title=The power of intermittent fasting | vauthors = Mosley M |date=5 August 2012 |publisher=BBC Health |access-date=14 January 2019 |archive-url=https://web.archive.org/web/20190216104602/https://www.bbc.com/news/health-19112549 |archive-date=16 February 2019 |url-status=live }}{{Cite web |url=https://www.bbc.co.uk/iplayer/episode/b01lxyzc/horizon-20122013-3-eat-fast-and-live-longer |title=Horizon - Eat, Fast and Live Longer |date=6 August 2012 |publisher=BBC iPlayer |access-date=14 January 2019 |archive-url=https://web.archive.org/web/20190105010627/https://www.bbc.co.uk/iplayer/episode/b01lxyzc/horizon-20122013-3-eat-fast-and-live-longer |archive-date=5 January 2019 |url-status=live }}{{cite web | title=What the science says about the 5:2 intermittent fasting diet | website=ABC Everyday|publisher= Australian Broadcasting Corporation | date=10 February 2020 | url=https://www.abc.net.au/everyday/what-the-science-says-about-the-5-2-intermittent-fasting-diet/11932126 | access-date=11 February 2021| vauthors = Wilson P |quote=This story, which was originally written by Pamela Wilson and published by ABC Health and Wellbeing, has been reviewed by Dr Rosemary Stanton OAM, nutritionist and visiting fellow, School of Medical Sciences, University of NSW, and was updated in 2019. Posted 5 Feb 2020, updated 10 Feb 2020}}
• Periodic fasting or whole-day fasting involves intermittent periods of water fasting longer than 24 hours.{{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 }}

The science concerning intermittent fasting is preliminary and uncertain due to an absence of studies on its long-term effects.{{cite journal | vauthors = Evert AB, Dennison M, Gardner CD, Garvey WT, Lau KH, MacLeod J, Mitri J, Pereira RF, Rawlings K, Robinson S, Saslow L, Uelmen S, Urbanski PB, Yancy WS | title = Nutrition Therapy for Adults With Diabetes or Prediabetes: A Consensus Report | journal = Diabetes Care | volume = 42 | issue = 5 | pages = 731–754 | date = May 2019 | pmid = 31000505 | pmc = 7011201 | doi = 10.2337/dci19-0014 | type = Professional society guidelines }}{{Cite book |last=Minister of Health NZ |url=https://www.health.govt.nz/publication/clinical-guidelines-weight-management-new-zealand-adults |title=Clinical guidelines for weight management in New Zealand adults |date=2017 |publisher=Ministry of Health |isbn=978-1-988539-16-4 |type=National guidelines |access-date=1 November 2019 |archive-url=https://web.archive.org/web/20191101050034/https://www.health.govt.nz/publication/clinical-guidelines-weight-management-new-zealand-adults |archive-date=1 November 2019 |url-status=live }} Preliminary evidence indicates that intermittent fasting may be effective for weight loss, may decrease insulin resistance and fasting insulin, and may improve cardiovascular and metabolic health, although the long term sustainability of these effects has not been studied.

There is limited evidence that intermittent fasting produces weight loss comparable to a calorie-restricted diet.{{cite journal | vauthors = Davis CS, Clarke RE, Coulter SN, Rounsefell KN, Walker RE, Rauch CE, Huggins CE, Ryan L | title = Intermittent energy restriction and weight loss: a systematic review | journal = European Journal of Clinical Nutrition | volume = 70 | issue = 3 | pages = 292–9 | date = March 2016 | pmid = 26603882 | doi = 10.1038/ejcn.2015.195 | s2cid = 24189275 }} Most studies on intermittent fasting in humans have observed weight loss, ranging from 2.5% to 9.9%.{{cite journal | vauthors = Ekmekcioglu C | title = Nutrition and longevity - From mechanisms to uncertainties | journal = Critical Reviews in Food Science and Nutrition | volume = 60 | issue = 18 | pages = 3063–3082 | date = 21 October 2019 | pmid = 31631676 | doi = 10.1080/10408398.2019.1676698 | type = Review | s2cid = 204815279 }}{{cite journal | vauthors = Stockman MC, Thomas D, Burke J, Apovian CM | title = Intermittent Fasting: Is the Wait Worth the Weight? | journal = Current Obesity Reports | volume = 7 | issue = 2 | pages = 172–185 | date = June 2018 | pmid = 29700718 | pmc = 5959807 | doi = 10.1007/s13679-018-0308-9 | type = Review | quote = Nearly all IF studies have resulted in some degree of weight loss, ranging from 2.5–9.9%, and associated fat mass loss. }}

The reductions in body weight can be attributed to the loss of fat mass and some lean mass.{{Cite journal|last1=Fanti|first1=Maura|last2=Mishra|first2=Amrendra|last3=Longo|first3=Valter D.|last4=Brandhorst|first4=Sebastian|date=29 January 2021|title=Time-Restricted Eating, Intermittent Fasting, and Fasting-Mimicking Diets in Weight Loss|url=http://dx.doi.org/10.1007/s13679-021-00424-2|journal=Current Obesity Reports|volume=10|issue=2|pages=70–80|doi=10.1007/s13679-021-00424-2|pmid=33512641|s2cid=231747084|issn=2162-4968}}{{Cite journal|last1=Gabel|first1=Kelsey|last2=Cienfuegos|first2=Sofia|last3=Kalam|first3=Faiza|last4=Ezpeleta|first4=Mark|last5=Varady|first5=Krista A.|date=26 March 2021|title=Time-Restricted Eating to Improve Cardiovascular Health|url=http://dx.doi.org/10.1007/s11883-021-00922-7|journal=Current Atherosclerosis Reports|volume=23|issue=5|page=22|doi=10.1007/s11883-021-00922-7 |pmid=33772388|pmc=8218778|issn=1523-3804}} For time restricted eating the ratio of weight loss is 4:1 for fat mass to lean mass, respectively. Alternate-day fasting does not affect lean body mass,{{cite journal | vauthors = Alhamdan BA, Garcia-Alvarez A, Alzahrnai AH, Karanxha J, Stretchberry DR, Contrera KJ, Utria AF, Cheskin LJ | title = Alternate-day versus daily energy restriction diets: which is more effective for weight loss? A systematic review and meta-analysis | journal = Obesity Science & Practice | volume = 2 | issue = 3 | pages = 293–302 | date = September 2016 | pmid = 27708846 | pmc = 5043510 | doi = 10.1002/osp4.52 }} although one review found a small decrease.{{cite journal | vauthors = Roman YM, Dominguez MC, Easow TM, Pasupuleti V, White CM, Hernandez AV | title = Effects of intermittent versus continuous dieting on weight and body composition in obese and overweight people: a systematic review and meta-analysis of randomized controlled trials | journal = International Journal of Obesity | volume = 43 | issue = 10 | pages = 2017–2027 | date = October 2019 | pmid = 30206335 | doi = 10.1038/s41366-018-0204-0 | s2cid = 52188900 | hdl = 10757/624649 }}

Alternate-day fasting improves cardiovascular and metabolic biomarkers similarly to a calorie restriction diet in people who are overweight, obese or have metabolic syndrome.{{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 }} As of 2021, it remains uncertain whether intermittent fasting could prevent cardiovascular disease.{{cite journal | vauthors = Allaf M, Elghazaly H, Mohamed OG, Fareen MF, Zaman S, Salmasi AM, Tsilidis K, Dehghan A | title = Intermittent fasting for the prevention of cardiovascular disease | journal = The Cochrane Database of Systematic Reviews | volume = 1 | issue = 3 | pages = CD013496 | date = January 2021 | pmid = 33512717 | pmc = 8092432 | doi = 10.1002/14651858.CD013496.pub2 | collaboration = Cochrane Heart Group }}

Intermittent fasting has not been studied in children, elderly, or underweight people, and may be harmful in these populations.{{cite journal | vauthors = Longo VD, Mattson MP | title = Fasting: molecular mechanisms and clinical applications | journal = Cell Metabolism | volume = 19 | issue = 2 | pages = 181–92 | date = February 2014 | pmid = 24440038 | pmc = 3946160 | doi = 10.1016/j.cmet.2013.12.008 }} Intermittent fasting is not recommended for people who are not overweight, and the long-term sustainability of intermittent fasting is unknown {{as of|2018|lc=yes}}.{{cite journal | vauthors = Harris L, McGarty A, Hutchison L, Ells L, Hankey C | title = Short-term intermittent energy restriction interventions for weight management: a systematic review and meta-analysis | journal = Obesity Reviews | volume = 19 | issue = 1 | pages = 1–13 | date = January 2018 | pmid = 28975722 | doi = 10.1111/obr.12593 | s2cid = 23760594 }}

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 factors in overweight or obese adults.{{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}}

Intermittent fasting is not recommended to treat cancer in France,{{Cite web |url=https://www6.inra.fr/nacre/Le-reseau-NACRe/Outils-pour-professionnels/Rapport-NACRe-jeune-regimes-restrictifs-cancer-2017 |title=Réseau NACRe - Réseau National Alimentation Cancer Recherche - Rapport NACRe jeûne regimes restrictifs cancer 2017 |date=November 2017 |website=www6.inra.fr |language=fr-FR |access-date=19 September 2018 |archive-url=https://web.archive.org/web/20180920100940/https://www6.inra.fr/nacre/Le-reseau-NACRe/Outils-pour-professionnels/Rapport-NACRe-jeune-regimes-restrictifs-cancer-2017 |archive-date=20 September 2018 |url-status=live }}{{Cite book |url=https://www.prescrire.org/fr/3/31/55335/0/NewsDetails.aspx |title=Régime et évolution d'un cancer |date=1 October 2018 |publisher=Rev Prescrire |page=773 |access-date=6 October 2019 |archive-url=https://web.archive.org/web/20191006001312/https://www.prescrire.org/fr/3/31/55335/0/NewsDetails.aspx |archive-date=6 October 2019 |url-status=live }} the United Kingdom,{{Cite web |url=https://www.nhs.uk/news/food-and-diet/no-proof-52-diet-prevents-cancer/ |title=No proof 5:2 diet prevents cancer |date=3 October 2018 |website=nhs.uk |access-date=17 October 2019 |archive-url=https://web.archive.org/web/20191017144627/https://www.nhs.uk/news/food-and-diet/no-proof-52-diet-prevents-cancer/ |archive-date=17 October 2019 |url-status=live }} or the United States,{{Cite book |title=American Cancer Society Complete Guide to Complementary and Alternative Cancer Therapies |publisher=American Cancer Society |year=2009 |isbn=978-0-944235-71-3 | veditors = Russell J, Rovere A |edition=2nd |chapter=Fasting |chapter-url=https://archive.org/details/americancancerso0000unse |chapter-url-access=registration}} although a few small-scale clinical studies suggest that it may reduce chemotherapy side effects.{{cite journal | vauthors = Smith LA, O'Flanagan CH, Bowers LW, Allott EH, Hursting SD | title = Translating Mechanism-Based Strategies to Break the Obesity-Cancer Link: A Narrative Review | journal = Journal of the Academy of Nutrition and Dietetics | volume = 118 | issue = 4 | pages = 652–667 | date = April 2018 | pmid = 29102513 | pmc = 5869082 | doi = 10.1016/j.jand.2017.08.112 | type = Narrative review }}{{cite journal | vauthors = O'Flanagan CH, Smith LA, McDonell SB, Hursting SD | title = When less may be more: calorie restriction and response to cancer therapy | journal = BMC Medicine | volume = 15 | issue = 1 | pages = 106 | date = May 2017 | pmid = 28539118 | pmc = 5442682 | doi = 10.1186/s12916-017-0873-x | type = Mini-review | doi-access = free }} Periodic fasting may have a minor effect on chronic pain and mood disorders.{{cite journal | vauthors = Brain K, Burrows TL, Rollo ME, Chai LK, Clarke ED, Hayes C, Hodson FJ, Collins CE | title = A systematic review and meta-analysis of nutrition interventions for chronic noncancer pain | journal = Journal of Human Nutrition and Dietetics | volume = 32 | issue = 2 | pages = 198–225 | date = April 2019 | pmid = 30294938 | doi = 10.1111/jhn.12601 | s2cid = 52933736 }}{{cite journal | vauthors = Fond G, Macgregor A, Leboyer M, Michalsen A | title = Fasting in mood disorders: neurobiology and effectiveness. A review of the literature | journal = Psychiatry Research | volume = 209 | issue = 3 | pages = 253–8 | date = October 2013 | pmid = 23332541 | doi = 10.1016/j.psychres.2012.12.018 | url = https://www.hal.inserm.fr/inserm-00789122/file/FASTING_revised_manuscript_11_12_12.pdf | access-date = 23 October 2019 | url-status = live | s2cid = 39700065 | archive-url = https://web.archive.org/web/20190430203604/https://www.hal.inserm.fr/inserm-00789122/file/FASTING_revised_manuscript_11_12_12.pdf | archive-date = 30 April 2019 }}{{cite journal | vauthors = Michalsen A | title = Prolonged fasting as a method of mood enhancement in chronic pain syndromes: a review of clinical evidence and mechanisms | journal = Current Pain and Headache Reports | volume = 14 | issue = 2 | pages = 80–7 | date = April 2010 | pmid = 20425196 | doi = 10.1007/s11916-010-0104-z | s2cid = 23707195 }}

Athletic performance does not benefit from intermittent fasting.{{cite journal | vauthors = Levy E, Chu T | title = Intermittent Fasting and Its Effects on Athletic Performance: A Review | journal = Current Sports Medicine Reports | volume = 18 | issue = 7 | pages = 266–269 | date = July 2019 | pmid = 31283627 | doi = 10.1249/JSR.0000000000000614 | s2cid = 195828287 }} Overnight fasting before exercise increases lipolysis, but reduces performance in prolonged exercise (more than 60 min).{{cite journal | vauthors = Vieira AF, Costa RR, Macedo RC, Coconcelli L, Kruel LF | title = Effects of aerobic exercise performed in fasted v. fed state on fat and carbohydrate metabolism in adults: a systematic review and meta-analysis | journal = The British Journal of Nutrition | volume = 116 | issue = 7 | pages = 1153–1164 | date = October 2016 | pmid = 27609363 | doi = 10.1017/S0007114516003160 | type = Meta-analysis | s2cid = 25607885 }}{{cite journal | vauthors = Aird TP, Davies RW, Carson BP | title = Effects of fasted vs fed-state exercise on performance and post-exercise metabolism: A systematic review and meta-analysis | journal = Scandinavian Journal of Medicine & Science in Sports | volume = 28 | issue = 5 | pages = 1476–1493 | date = May 2018 | pmid = 29315892 | doi = 10.1111/sms.13054 | type = Meta-analysis | s2cid = 4962378 | hdl = 10344/6776 }}

There is preliminary evidence that intermittent fasting appears safe for people without diabetes or eating disorders.

Reviews of preliminary clinical studies found that short-term intermittent fasting may produce minor side effects, such as continuous feelings of hunger, irritability, dizziness, nausea, headaches, and impaired thinking, although these effects disappear within a month from beginning the fasting practice.{{cite journal|vauthors=de Cabo R, Mattson MP|date=December 2019|title=Effects of Intermittent Fasting on Health, Aging, and Disease|journal=The New England Journal of Medicine|volume=381|issue=26|pages=2541–2551|doi=10.1056/NEJMra1905136|pmid=31881139|s2cid=209498984}}{{cite journal | vauthors = Horne BD, Muhlestein JB, Anderson JL | title = Health effects of intermittent fasting: hormesis or harm? A systematic review | journal = The American Journal of Clinical Nutrition | volume = 102 | issue = 2 | pages = 464–70 | date = August 2015 | pmid = 26135345 | doi = 10.3945/ajcn.115.109553 | doi-access = free }} A 2018 systematic review found no major adverse effects. Intermittent fasting is not recommended for pregnant or breastfeeding women, growing children and adolescents, the elderly, or individuals with or vulnerable to eating disorders.

Tolerance of a diet is a determinant of the potential effectiveness and maintenance of benefits obtained, such as weight loss or biomarker improvement.{{cite journal | vauthors = Freire R | title = Scientific evidence of diets for weight loss: Different macronutrient composition, intermittent fasting, and popular diets | journal = Nutrition | volume = 69 | pages = 110549 | date = January 2020 | pmid = 31525701 | doi = 10.1016/j.nut.2019.07.001 | s2cid = 198280773 }} A 2019 review found that drop-out rates varied widely from 2% to 38% for intermittent fasting, and from 0% to 50% for calorie restriction diet.

Preliminary research indicates that fasting may induce a transition through four states:

1. The fed state or absorptive state during satiety, when the primary fuel source is glucose and body fat storage is active, lasting for about 4 hours;{{cite journal | vauthors = Monnier L, Colette C, Lapinski H, Boniface H | title = Self-monitoring of blood glucose in diabetic patients: from the least common denominator to the greatest common multiple | journal = Diabetes & Metabolism | volume = 30 | issue = 2 | pages = 113–9 | date = April 2004 | pmid = 15223983 | doi = 10.1016/S1262-3636(07)70097-6 | url = https://www.em-consulte.com/en/article/80286 | access-date = 8 November 2019 | publisher = Elsevier Masson | url-status = live | archive-url = https://web.archive.org/web/20191108113458/https://www.em-consulte.com/en/article/80286 | archive-date = 8 November 2019 | type = Mini-review }}{{Cite journal | vauthors = Drăgoi CM |date=10 July 2019 |title=Insights into Chrononutrition: The Innermost Interplay Amongst Nutrition, Metabolism and the Circadian Clock, in the Context of Epigenetic Reprogramming |journal=Farmacia |volume=67 |issue=4 |pages=557–571 |doi=10.31925/farmacia.2019.4.2|s2cid=199075075 }}
2. The postabsorptive state, lasting for up to 18 hours, when glucagon is secreted and the body uses liver glucose reserves as a fuel source;
3. The fasted state, transitioning progressively to other reserves, such as fat, lactic acid, and alanine, as fuel sources, when the liver glucose reserves are depleted, occurring after 12 to 36 hours of continued fast;{{cite journal | vauthors = Cahill GF | title = Fuel metabolism in starvation | journal = Annual Review of Nutrition | volume = 26 | issue = 1 | pages = 1–22 | date = August 2006 | pmid = 16848698 | doi = 10.1146/annurev.nutr.26.061505.111258 | type = Narrative Review }}{{Cite book |title=Handbook of Physiology: a Critical, Comprehensive Presentation of Physiological Knowledge and Concepts |vauthors=Renold AE |date=1965 |publisher=American Physiological Society |chapter=Section 5: Adipose Tissue |chapter-url={{google books |plainurl=y |id=1IPtxQEACAAJ}}}}
4. The shift from preferential lipid synthesis and fat storage, to the mobilization of fat (in the form of free fatty acids), metabolized into fatty acid-derived ketones to provide energy.{{cite journal | vauthors = Lechner K, von Schacky C, McKenzie AL, Worm N, Nixdorff U, Lechner B, Kränkel N, Halle M, Krauss RM, Scherr J | title = Lifestyle factors and high-risk atherosclerosis: Pathways and mechanisms beyond traditional risk factors | journal = European Journal of Preventive Cardiology | volume = 27 | issue = 4 | pages = 394–406 | date = March 2020 | pmid = 31408370 | pmc = 7065445 | doi = 10.1177/2047487319869400 }}{{cite journal | vauthors = Zubrzycki A, Cierpka-Kmiec K, Kmiec Z, Wronska A | title = The role of low-calorie diets and intermittent fasting in the treatment of obesity and type-2 diabetes | journal = Journal of Physiology and Pharmacology | volume = 69 | issue = 5 | date = October 2018 | pmid = 30683819 | doi = 10.26402/jpp.2018.5.02 | type = Review }} Some authors call this transition the "metabolic switch".{{cite journal | vauthors = Anton SD, Moehl K, Donahoo WT, Marosi K, Lee SA, Mainous AG, Leeuwenburgh C, Mattson MP | title = Flipping the Metabolic Switch: Understanding and Applying the Health Benefits of Fasting | journal = Obesity | volume = 26 | issue = 2 | pages = 254–268 | date = February 2018 | pmid = 29086496 | pmc = 5783752 | doi = 10.1002/oby.22065 | type = Review }}{{cite journal | vauthors = Mattson MP, Moehl K, Ghena N, Schmaedick M, Cheng A | title = Intermittent metabolic switching, neuroplasticity and brain health | journal = Nature Reviews. Neuroscience | volume = 19 | issue = 2 | pages = 63–80 | date = February 2018 | pmid = 29321682 | pmc = 5913738 | doi = 10.1038/nrn.2017.156 | type = Review }}

A 2019 review of weight-change interventions, including alternate day fasting, time-restricted feeding, exercise and overeating, found that body weight homeostasis could not precisely correct "energetic errors" – the loss or gain of calories – in the short-term.{{cite journal | vauthors = Levitsky DA, Sewall A, Zhong Y, Barre L, Shoen S, Agaronnik N, LeClair JL, Zhuo W, Pacanowski C | title = Quantifying the imprecision of energy intake of humans to compensate for imposed energetic errors: A challenge to the physiological control of human food intake | journal = Appetite | volume = 133 | pages = 337–343 | date = February 2019 | pmid = 30476522 | doi = 10.1016/j.appet.2018.11.017 | s2cid = 53712116 }}

Another pathway for effects of meal timing on metabolism lies in the influence of the circadian rhythm over the endocrine system, especially on glucose metabolism and leptin.{{cite journal |last1=Rüger |first1=M |last2=Scheer |first2=FA |title=Effects of circadian disruption on the cardiometabolic system. |journal=Reviews in Endocrine and Metabolic Disorders |date=December 2009 |volume=10 |issue=4 |pages=245–60 |doi=10.1007/s11154-009-9122-8 |pmid=19784781|pmc=3026852 }} Preliminary studies found that eating when melatonin is secreted {{ndash}} during darkness and commonly when sleeping at night {{ndash}} is associated with increased glucose levels in young healthy adults, and obesity and cardiovascular disorders in less healthy individuals.{{cite journal |last1=Manoogian |first1=ENC |last2=Chaix |first2=A |last3=Panda |first3=S |title=When to Eat: The Importance of Eating Patterns in Health and Disease. |journal=Journal of Biological Rhythms |date=December 2019 |volume=34 |issue=6 |pages=579–581 |doi=10.1177/0748730419892105 |pmid=31813351|pmc=7213043 }} Reviews on obesity prevention concluded that "meal timing appears as a new potential target in weight control strategies" and suggest that "timing and content of food intake, physical activity, and sleep may be modulated to counteract" circadian and metabolic genetic predispositions to obesity.{{cite journal |last1=Beccuti |first1=G |last2=Monagheddu |first2=C |last3=Evangelista |first3=A |last4=Ciccone |first4=G |last5=Broglio |first5=F |last6=Soldati |first6=L |last7=Bo |first7=S |title=Timing of food intake: Sounding the alarm about metabolic impairments? A systematic review. |journal=Pharmacological Research |date=November 2017 |volume=125 |issue=Pt B |pages=132–141 |doi=10.1016/j.phrs.2017.09.005 |pmid=28928073|hdl=2318/1671160 |s2cid=37837201 }}{{cite journal |last1=Covassin |first1=N |last2=Singh |first2=P |last3=Somers |first3=VK |title=Keeping Up With the Clock: Circadian Disruption and Obesity Risk. |journal=Hypertension |date=November 2016 |volume=68 |issue=5 |pages=1081–1090 |doi=10.1161/HYPERTENSIONAHA.116.06588 |pmid=27620394|pmc=5063707 }}

Other feeding schemes, such as hypocaloric feeding{{cite journal | vauthors = Marik PE, Hooper MH | title = Normocaloric versus hypocaloric feeding on the outcomes of ICU patients: a systematic review and meta-analysis | journal = Intensive Care Medicine | volume = 42 | issue = 3 | pages = 316–323 | date = March 2016 | pmid = 26556615 | doi = 10.1007/s00134-015-4131-4 | s2cid = 37653149 }} and intermittent feeding, also called bolus feeding were under study.{{cite journal | vauthors = Singer P, Blaser AR, Berger MM, Alhazzani W, Calder PC, Casaer MP, Hiesmayr M, Mayer K, Montejo JC, Pichard C, Preiser JC, van Zanten AR, Oczkowski S, Szczeklik W, Bischoff SC | title = ESPEN guideline on clinical nutrition in the intensive care unit | journal = Clinical Nutrition | volume = 38 | issue = 1 | pages = 48–79 | date = February 2019 | pmid = 30348463 | doi = 10.1016/j.clnu.2018.08.037 | s2cid = 53036546 | doi-access=free | title-link=doi }} A 2019 meta-analysis found that intermittent feeding may be more beneficial for premature infants, although better designed studies are required to devise clinical practices.{{cite journal | vauthors = Wang Y, Zhu W, Luo BR | title = Continuous feeding versus intermittent bolus feeding for premature infants with low birth weight: a meta-analysis of randomized controlled trials | journal = European Journal of Clinical Nutrition | volume = 74 | issue = 5 | pages = 775–783 | date = May 2020 | pmid = 31659243 | pmc = 7222868 | doi = 10.1038/s41430-019-0522-x | type = Meta-analysis | s2cid = 204948008 }} In adults, reviews have not found intermittent feeding to increase glucose variability or gastrointestinal intolerance.{{cite journal | vauthors = Bear DE, Hart N, Puthucheary Z | title = Continuous or intermittent feeding: pros and cons | journal = Current Opinion in Critical Care | volume = 24 | issue = 4 | pages = 256–261 | date = August 2018 | pmid = 29877877 | doi = 10.1097/MCC.0000000000000513 | s2cid = 46984630 | url = https://qmro.qmul.ac.uk/xmlui/handle/123456789/57045 | type = Review }}{{cite journal | vauthors = Van Dyck L, Casaer MP | title = Intermittent or continuous feeding: any difference during the first week? | journal = Current Opinion in Critical Care | volume = 25 | issue = 4 | pages = 356–362 | date = August 2019 | pmid = 31107308 | doi = 10.1097/MCC.0000000000000617 | s2cid = 159039594 | type = Meta-analysis }} A meta-analysis found intermittent feeding had no influence on gastric residual volumes and aspiration, pneumonia, mortality nor morbidity in people with a trauma, but increased the risk of diarrhea.

Intermittent fasting, or "skip-a-day" feeding, is supposedly the most common feeding strategy for poultry in broiler breeder farms worldwide, as an alternative to adding bulky fibers to the diet to reduce growth. It is perceived as welfare-reducing and thus illegal in several European countries including Sweden. Intermittent fasting in poultry appears to increase food consumption but reduce appetitive behaviors such as foraging.{{Cite book | vauthors = Lindholm C |url={{google books |plainurl=y |id=6H64DwAAQBAJ}} |title=Intermittent fasting in chickens: Physiological mechanisms and welfare implications for broiler breeders |date=2019 |publisher=Linköping University Electronic Press |isbn=978-91-7685-018-3}}

{{Main|Fasting in religion}}

Some different types of fastings exist in some religious practices. These include the Black Fast of Christianity (commonly practiced during Lent), Vrata (Hinduism), Ramadan (Islam), Yom Kippur (Judaism), Fast Sunday (The Church of Jesus Christ of Latter-day Saints), Jain fasting, and Buddhist fasting. Religious fasting practices may only require abstinence from certain foods or last for a short period of time and cause negligible effects.

A Vrata/Nombu is observed either as an independent private ritual at a date of one's choice, as part of a particular ceremony such as wedding, or as a part of a major festival such as Diwali (Lakshmi, festival of lights), Shivaratri (Shiva), Navratri (Durga or Rama), Kandasashti (Muruga), Ekadashi (Krishna, Vishnu avatars).{{Cite book |last=Michaels |first=Axel |url=https://books.google.com/books?id=DSaxCgAAQBAJ |title=Homo Ritualis: Hindu Ritual and Its Significance for Ritual Theory |date=2016 |publisher=Oxford University Press |isbn=978-0-19-026263-1 |language=en}}{{Cite book |last1=Harlan |first1=Lindsey |url=https://books.google.com/books?id=7HLrPYOe38gC |title=Religion and Rajput Women: The Ethic of Protection in Contemporary Narratives |last2=Harlan |first2=Professor of Religious Studies Lindsey |date=1992-01-01 |publisher=University of California Press |isbn=978-0-520-07339-5 |language=en}}{{Cite book |last=Pearson |first=Anne Mackenzie |url=http://archive.org/details/becauseitgivesme0000pear |title=Because it gives me peace of mind : ritual fasts in the religious lives of Hindu women |date=1996 |publisher=Albany : State University of New York Press |others=Internet Archive |isbn=978-0-585-06811-4}}{{Cite web |last=Retail |first=Mythili |date=2022-04-11 |title=Sashti Viratham 2022 Procedure, Benefits of Sashti Viratham |url=https://vgocart.com/sashti-viratham-2022-procedure-benefits-monthly-sashti/ |access-date=2022-12-13 |language=en-US}}

In Christianity, many adherents of Christian denominations including Catholics, Lutherans, Methodists, Anglicans, and the Orthodox, often observe the Friday Fast throughout the year, which commonly includes abstinence from meat.{{cite book | vauthors = Boyers L |title=Intermittent Fasting Basics: Your Guide to the Essentials of Intermittent Fasting—and How It Can Work for You! |date=2019 |publisher=Simon and Schuster |isbn=978-1-5072-1056-7 |page=19 |language=en}} Throughout the liturgical season of Lent (and especially on Ash Wednesday and Good Friday) in the Christian calendar, many Christians practice a form of intermittent fasting in which one can consume two collations and one full meal; others practice the Black Fast, in which no food or water is consumed until after sunset with prayer.{{cite web|url=http://glctulsa.org/wp-content/uploads/2016/02/Fasting-Guidelines-Rev-2016.pdf|title=Fasting Guidelines|publisher=Lutheran Church–Missouri Synod|language=en|year=2016|access-date=17 March 2018|archive-url=https://web.archive.org/web/20180317164934/http://glctulsa.org/wp-content/uploads/2016/02/Fasting-Guidelines-Rev-2016.pdf|archive-date=17 March 2018|url-status=live}}{{cite book| vauthors = Stravinskas PM, Shaw RB |title=Our Sunday Visitor's Catholic Encyclopedia|date=1 September 1998|publisher=Our Sunday Visitor|language=en|isbn=978-0-87973-669-9|quote=The so-called black fast refers to a day or days of penance on which only one meal is allowed, and that in the evening. The prescription of this type of fast not only forbids the partaking of meats but also of all dairy products, such as eggs, butter, cheese, and milk. Wine and other alcoholic beverages are forbidden as well. In short, only bread, water, and vegetables form part of the diet for one following such a fast.}}

In Buddhism, fasting is undertaken as part of the monastic training of Theravada Buddhist monks, who fast daily from noon to sunrise of the next day.{{Cite book | vauthors = Johnston WM |url={{google books |plainurl=y |id=iepJAgAAQBAJ}}|title=Encyclopedia of Monasticism |date=4 December 2013 |publisher=Routledge |isbn=978-1-136-78716-4 |pages=467 |access-date=26 June 2019 |archive-url=https://web.archive.org/web/20191222173541/https://books.google.com/books?id=iepJAgAAQBAJ |archive-date=22 December 2019 |url-status=live }} This daily fasting pattern may be undertaken by laypeople following the eight precepts.{{Cite book | vauthors = Cottrell T, Zigmond D |url={{google books |plainurl=y |id=3aC0DAAAQBAJ}}|title=Buddha's Diet: The Ancient Art of Losing Weight Without Losing Your Mind |date=6 September 2016 |publisher=Running Press |isbn=978-0-7624-6046-5 |pages=26–27 }}

During Ramadan, Islamic practices are similar to intermittent fasting by not eating or drinking from dawn until sunset, while permitting food intake in the morning before dawn and in the evening after dusk for 30 days.{{Cite web|last=Elnakib|first=Sara|date=12 April 2021|title=Ramadan The Practice of Fasting|url=https://www.eatright.org/health/lifestyle/culture-and-traditions/ramadan--the-practice-of-fasting|access-date=21 September 2021|website=Eat Right: Academy of Nutrition and Dietetics}} A meta-analysis on the health of Muslims during Ramadan shows significant weight loss during the fasting period of up to {{convert|1.51|kg|lbs}}, but this weight was regained within about two weeks thereafter.{{cite journal | vauthors = Sadeghirad B, Motaghipisheh S, Kolahdooz F, Zahedi MJ, Haghdoost AA | title = Islamic fasting and weight loss: a systematic review and meta-analysis | journal = Public Health Nutrition | volume = 17 | issue = 2 | pages = 396–406 | date = February 2014 | pmid = 23182306 | doi = 10.1017/S1368980012005046 | doi-broken-date = 27 November 2024 | pmc = 10282472 | s2cid = 6162935 }} The analysis concluded that "Ramadan provides an opportunity to lose weight, but structured and consistent lifestyle modifications are necessary to achieve lasting weight loss." One review found similarities between Ramadan and time-restricted feeding, with the main dissimilarity being the disallowance of water drinking with Islamic fasting.{{cite journal | vauthors = Ismail S, Manaf RA, Mahmud A | title = Comparison of time-restricted feeding and Islamic fasting: a scoping review | journal = Eastern Mediterranean Health Journal | volume = 25 | issue = 4 | pages = 239–245 | date = June 2019 | pmid = 31210344 | doi = 10.26719/emhj.19.011 | url = http://www.emro.who.int/emhj-volume-25-2019/volume-25-issue-4/comparison-of-time-restricted-feeding-and-islamic-fasting-a-scoping-review.html | access-date = 16 October 2019 | publisher = World Health Organization Regional Office for the Eastern Mediterranean | s2cid = 96438878 | url-status = live | archive-url = https://web.archive.org/web/20191016064258/http://www.emro.who.int/emhj-volume-25-2019/volume-25-issue-4/comparison-of-time-restricted-feeding-and-islamic-fasting-a-scoping-review.html | archive-date = 16 October 2019 | type = Review }} In a 2020 review, Ramadan fasting caused a significant decrease in LDL cholesterol levels, and a slight decline in total cholesterol.{{Cite journal|last1=Hoddy|first1=Kristin K.|last2=Marlatt|first2=Kara L.|last3=Çetinkaya|first3=Hatice|last4=Ravussin|first4=Eric|date=July 2020|title=Intermittent Fasting and Metabolic Health: From Religious Fast to Time-Restricted Feeding|url=http://dx.doi.org/10.1002/oby.22829|journal=Obesity|volume=28|issue=S1|pages=S29–S37|doi=10.1002/oby.22829|pmid=32700827|pmc=7419159 |issn=1930-7381}}

File:Iftar Serving for fasting people in the holy shrine of Imam Reza 05 ().jpg]]

A review of the metabolic effects of fasting showed that religious fasting proved to be beneficial in terms of "body weight and glycemia, cardiometabolic risk markers, and oxidative stress parameters", where animals, in the study, that followed a diet regimen consistent with that of religious fasting, were observed to have weight loss in addition to "lowered plasma levels of glucose, triacylglycerols, and insulin growth factor-1". Negative effects of Ramadan fasting include increased risk of hypoglycemia in diabetics, as well as inadequate levels of certain nutrients. Ramadan disallows fluids during the fasting period. This type of fasting would be hazardous for pregnant women, as it is associated with risks of inducing labor and causing gestational diabetes, although it does not appear to affect the child's weight.{{cite journal | vauthors = Glazier JD, Hayes DJ, Hussain S, D'Souza SW, Whitcombe J, Heazell AE, Ashton N | title = The effect of Ramadan fasting during pregnancy on perinatal outcomes: a systematic review and meta-analysis | journal = BMC Pregnancy and Childbirth | volume = 18 | issue = 1 | pages = 421 | date = October 2018 | pmid = 30359228 | pmc = 6202808 | doi = 10.1186/s12884-018-2048-y | doi-access = free }}{{cite journal | vauthors = Mirghani HM, Hamud OA | title = The effect of maternal diet restriction on pregnancy outcome | journal = American Journal of Perinatology | volume = 23 | issue = 1 | pages = 21–4 | date = January 2006 | pmid = 16450268 | doi = 10.1055/s-2005-923435 | s2cid = 260001799 }} For these reasons, pregnant women, as well as children who have not reached puberty, the elderly, those who are physically or mentally incapable of fasting, travelers, and breast-feeding mothers are often exempt from religious fasting – Ramadan being one example. Ramadan diurnal intermittent fasting is associated with healthier lifestyle behaviors and a reduction in smoking rate by more than 50% among university students.{{Cite journal |last1=Alotaibi |first1=Mohammed I. |last2=Elsamad |first2=Ghadir |last3=Aljardahi |first3=Abdulaziz N. |last4=Alghamdi |first4=Ahmed N. |last5=Alotaibi |first5=Abdulrahman I. |last6=Alorabi |first6=Hibah M. |last7=Alzahrani |first7=Khalid M. |last8=Abdel-Moneim |first8=Ahmed S. |date=2023-07-31 |title=Changes in dietary and lifestyle behaviors and mental stress among medical students upon Ramadan diurnal intermittent fasting: a prospective cohort study from Taif/Saudi Arabia |journal=BMC Public Health |volume=23 |issue=1 |pages=1462 |doi=10.1186/s12889-023-16385-1 |doi-access=free |issn=1471-2458 |pmc=10391762 |pmid=37525238}}

The American Heart Association (AHA) says that as with other "popular or fad diets", there is no good evidence of heart health benefits from intermittent fasting.{{cite journal |vauthors=Lichtenstein AH, Appel LJ, Vadiveloo M, Hu FB, Kris-Etherton PM, Rebholz CM, Sacks FM, Thorndike AN, Van Horn L, Wylie-Rosett J |title=2021 Dietary Guidance to Improve Cardiovascular Health: A Scientific Statement From the American Heart Association |journal=Circulation |volume=144 |issue=23 |pages=e472–e487 |date=December 2021 |pmid=34724806 |doi=10.1161/CIR.0000000000001031 |s2cid=240422142 |type=Review |quote=There is insufficient evidence to support any existing popular or fad diets such as the ketogenic diet and intermittent fasting to promote heart health. }}

The American Diabetes Association "found limited evidence about the safety and/or effects of intermittent fasting on type 1 diabetes" and preliminary results of weight loss for type 2 diabetes, and so does not recommend any specific dietary pattern for the management of diabetes until more research is done, recommending instead that "health care providers should focus on the key factors that are common among the patterns".

The National Institute on Aging states that although intermittent fasting showed weight loss success in several studies on obese or overweight individuals, it does not recommend intermittent fasting for non-overweight individuals because of uncertainties about its effectiveness and safety, especially for older adults.

Given the lack of advantage and the increased incidence of diarrhea, European guidelines do not recommend intermittent feeding for people in intensive care units.

According to NHS Choices, people considering the 5:2 diet should first consult a physician, as fasting can sometimes be unsafe.{{Cite web |url=http://www.nhs.uk/news/2013/01January/Pages/Does-the-5-2-intermittent-fasting-diet-work.aspx |title=News analysis: Does the 5:2 intermittent fasting diet work? |date=May 2013 |website=Health News |publisher=UK National Health Service - NHS Choices |access-date=23 November 2016 |archive-url=https://web.archive.org/web/20161109085837/http://www.nhs.uk/news/2013/01January/Pages/Does-the-5-2-intermittent-fasting-diet-work.aspx |archive-date=9 November 2016 |url-status=live }}

The New Zealand's Ministry of Health considers that intermittent fasting can be advised by doctors to some people, except diabetics, stating that these "diets can be as effective as other energy-restricted diets, and some people may find them easier to stick to" but there are possible side effects during fasting days such as "hunger, low energy levels, light-headedness and poor mental functioning" and note that healthy food must be chosen on non-fasting days.{{Cite web |url=https://www.health.govt.nz/your-health/healthy-living/food-activity-and-sleep/healthy-weight/help-managing-your-weight/popular-diets-review |title=Popular diets review |date=February 2018 |website=Ministry of Health NZ |type=National guidelines |access-date=1 November 2019 |archive-url=https://web.archive.org/web/20191101051338/https://www.health.govt.nz/your-health/healthy-living/food-activity-and-sleep/healthy-weight/help-managing-your-weight/popular-diets-review |archive-date=1 November 2019 |url-status=live }}

{{asof|2019}}, intermittent fasting was a common fad diet, attracting celebrity endorsements and public interest.{{Cite journal | vauthors = Arbolario K |date=26 August 2019 |title=Intermittent Fasting: Exposing The Dangers Of This Fad Diet |url=https://www.medicaldaily.com/intermittent-fasting-exposing-dangers-fad-diet-441728 |journal=Medical Daily |access-date=30 September 2019 |archive-url=https://web.archive.org/web/20190929232936/https://www.medicaldaily.com/intermittent-fasting-exposing-dangers-fad-diet-441728 |archive-date=29 September 2019 |url-status=live }}

Intermittent fasting (specifically the 5:2 diet) was popularized by Michael Mosley in the UK and Australia in 2012{{Cite web |url=http://www.nhs.uk/Livewell/loseweight/Pages/how-to-diet.aspx |title=How to diet |date=9 December 2011 |website=Live Well - NHS Choices |publisher=UK National Health Service |access-date=10 February 2014 |archive-url=https://web.archive.org/web/20140222004329/http://www.nhs.uk/livewell/loseweight/Pages/how-to-diet.aspx |archive-date=22 February 2014 |url-status=live }}{{cite journal | vauthors = Trueland J | title = Fast and effective? | journal = Nursing Standard | volume = 28 | issue = 16–18 | pages = 26–7 | date = December 2013 | pmid = 24345130 | doi = 10.7748/ns2013.12.28.16.26.s28 }} after the BBC2 television Horizon documentary Eat, Fast and Live Longer.{{Cite episode |title=Eat, Fast & Live Longer |url=http://www.bbc.co.uk/programmes/b01lxyzc |access-date=10 February 2014 |series=Horizon | vauthors = Mosley M |author-link=Michael Mosley |network=BBC |station=2 |number=49x03 |series-link=Horizon_(BBC_TV_series) |airdate=5 September 2012 |archive-url=https://web.archive.org/web/20140228022000/http://www.bbc.co.uk/programmes/b01lxyzc |archive-date=28 February 2014 |url-status=live }}{{Cite news | vauthors = Fleming M |url= https://www.theguardian.com/lifeandstyle/wordofmouth/2015/jan/27/fasting-facts-is-the-52-diet-too-good-to-be-true |title=Fasting facts: is the 5:2 diet too good to be true? |date=27 January 2015 |work=The Guardian |access-date=18 January 2018 |archive-url=https://web.archive.org/web/20180119060659/https://www.theguardian.com/lifeandstyle/wordofmouth/2015/jan/27/fasting-facts-is-the-52-diet-too-good-to-be-true |archive-date=19 January 2018 |url-status=live }}{{Cite web |url=https://www.forbes.com/sites/melaniehaiken/2013/05/17/hot-new-fasting-diet-from-europe-hits-the-u-s/ |title=The UK's Hot New 5:2 Diet Craze Hits The U.S. - Weight Loss Miracle? |date=17 May 2013 |website=Forbes |access-date=10 February 2014 |archive-url=https://web.archive.org/web/20140213103342/http://www.forbes.com/sites/melaniehaiken/2013/05/17/hot-new-fasting-diet-from-europe-hits-the-u-s/ |archive-date=13 February 2014 |url-status=live }}

In the United States, intermittent fasting became a trend in Silicon Valley, California.{{Cite news | vauthors = Solon O |url= https://www.theguardian.com/lifeandstyle/2017/sep/04/silicon-valley-ceo-fasting-trend-diet-is-it-safe |title=The Silicon Valley execs who don't eat for days: 'It's not dieting, it's biohacking' |date=4 September 2017 |work=The Guardian |access-date=5 November 2018 |archive-url=https://web.archive.org/web/20181105003834/https://www.theguardian.com/lifeandstyle/2017/sep/04/silicon-valley-ceo-fasting-trend-diet-is-it-safe |archive-date=5 November 2018 |url-status=live }} It was the most popular diet in 2018, according to a survey by the International Food Information Council.{{Cite news | vauthors = Kohok S |url=https://www.bbc.com/news/health-48478529 |title=Why is intermittent fasting so popular? |date=3 June 2019 |access-date=28 October 2019 |archive-url=https://web.archive.org/web/20190702205740/https://www.bbc.com/news/health-48478529 |archive-date=2 July 2019 |url-status=live }}{{Cite web |url=https://foodinsight.org/wp-content/uploads/2018/05/2018-FHS-Report-FINAL.pdf |title=2018 Food & Health Survey |date=2018 |website=foodinsight.org |publisher=International Food Information Council |access-date=28 October 2019 |archive-url=https://web.archive.org/web/20200103133204/https://foodinsight.org/wp-content/uploads/2018/05/2018-FHS-Report-FINAL.pdf |archive-date=3 January 2020 |url-status=live }}

{{As of|2019}}, interest in intermittent fasting led some companies to commercialize diet coaching, dietary supplements, and full meal packages.{{Cite news | vauthors = Giles T |url=https://www.bloomberg.com/news/articles/2018-04-24/intermittent-fasting-is-getting-silicon-valley-startup-treatment |title=Silicon Valley wants to cash in on fasting |date=24 April 2018 |work=Bloomberg News |access-date=8 November 2018 |archive-url=https://web.archive.org/web/20200425045506/https://www.bloomberg.com/news/articles/2018-04-24/intermittent-fasting-is-getting-silicon-valley-startup-treatment |archive-date=25 April 2020 |url-status=live }} These companies were criticized for offering expensive products or services that were not backed by science.{{Cite web |url=https://www.health.harvard.edu/heart-health/not-so-fast-pros-and-cons-of-the-newest-diet-trend |title=Not so fast: Pros and cons of the newest diet trend |date=31 July 2019 |publisher=Harvard Health Publishing, Harvard University Medical School |access-date=28 August 2019 |archive-url=https://web.archive.org/web/20190824002608/https://www.health.harvard.edu/heart-health/not-so-fast-pros-and-cons-of-the-newest-diet-trend |archive-date=24 August 2019 |url-status=live }}

• List of diets

{{reflist}}

• [https://www.nytimes.com/2020/02/17/well/eat/the-benefits-of-intermittent-fasting.html The benefits of intermittent fasting] Jane E. Brody, The New York Times, 17 February 2020
• [https://sciencebasedmedicine.org/intermittent-fasting/ Intermittent fasting] Harriet Hall, Science-Based Medicine, December 2015
• [https://sciencebasedmedicine.org/does-intermittent-fasting-work/ Does Intermittent Fasting Work?] Steven Novella, Science-Based Medicine, June 2023

{{Diets}}

{{Fad diets}}

Category:Diets

Category:Eating behaviors of humans

Category:Fad diets

Category:Fasting