Intermittent fasting

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Intermittent fasting (IF) is an umbrella term for various diets that cycle between a period of fasting and non-fasting. Intermittent fasting can be used along with calorie restriction for weight loss.[1]


In some contexts, fasting allows the consumption of a limited amount of low-calorie beverages such as coffee or tea.[2]

One form of intermittent fasting, alternate day fasting (ADF), involves a 24-hour fast followed by a 24-hour non-fasting period. This is sometimes referred to as every other day fasting or every other day feeding. Alternate-day calorie restriction may prolong life span.[3]

Modified fasting involves limiting caloric intake (e.g., 20% of normal) on fasting days rather than none at all. A study suggests that this regimen may retain most of the benefits of intermittent fasting.[3] The scientific literature for intermittent fasting, in its various forms, was extensively reviewed in 2014.[4] Another form involves eating only one meal per day.[5]

More generally, forms may choose to specify various ratios of fasting to non-fasting periods. The BBC2 Horizon documentary Eat, Fast and Live Longer[6] covered people who committed to fasting two non-consecutive days per week. Known as the 5:2 diet, people consumed 400–500 calories (women) or 500–600 calories (men) during the days of fasting. During feed days, the diet was regular.[7]


A 2014 review done by Longo and Mattson shed light on intermittent fasting's role in adaptive cellular responses that reduce oxidative damage and inflammation, optimize energy metabolism, and bolster cellular production. The study showed how, in lower eukaryotes, chronic fasting extends longevity, in part, by reprogramming metabolic and stress resistance pathways. In rodents, intermittent fasting was shown to protect against diabetes, cancers, heart disease and neurodegeneration, while in humans it helps reduce obesity, hypertension, asthma, and rheumatoid arthritis.[8]

Animal studies[edit]

A scientific study of intermittent fasting in rats conducted in 1943 found that fasting rats one day out of two, three or four days prolonged the life span of rats (by 15-20% in the case of one day out of three), compared to rats that were allowed to eat whenever they wish. None of the intermittent fasting in the study had detrimental effects on growth.[9]

In one study, intermittent fasting has been shown to extend lifespan and increase resistance to age-related diseases in rodents, and improve the health of overweight humans. The study suggests that intermittent fasting may have benefits that are similar to the effects of caloric restriction (CR). Specifically, it has been proposed that intermittent fasting improves the cardiovascular and neurological systems.[10]

One study on mice suggests that benefits from intermittent fasting seems to be unrelated to an overall reduction in caloric intake.[11] Another study on rats dealt with the benefits of dietary restriction, including intermittent fasting.[12] Intermittent fasting may function as a form of nutritional hormesis.[13]

A 2007 review of alternate day fasting said, "the findings in animals suggest that ADF may effectively modulate several risk factors, thereby preventing chronic disease, and that ADF may modulate disease risk to an extent similar to that of CR. More research is required to establish definitively the consequences of ADF."[14]

Fasting episodes trigger the process of autophagy[15] which breaks down and recycles dysfunctional proteins and organelles, and perhaps also the process of apoptosis which does the same with cells.

In a specific vulnerable population, ADF may bring harm: A study on hypercholesterolaemic mice showed that food restriction by intermittent fasting induces diabetes and obesity and aggravates spontaneous atherosclerosis development. Non-hypercholesterolaemic (normal, wild) control mice lost fat and lowered cholesterol as expected.[16]

Human health[edit]

Studies on humans suggest possible benefits:[4]

  • Alternate-day fasting may encourage fat oxidation.[17]
  • Alternate-day fasting may reduce body weight, LDL, and triglyceride levels to the same degree regardless of maintenance of low fat or high fat diet on the feeding day.[18]


Intermittent fasting is widely used for fitness and weight loss support. Many actors such as Hugh Jackman and Dwayne Johnson have done intermittent fasting to get fit for specific roles.[19]

See also[edit]


  1. ^
  2. ^ "An Introduction to Intermittent Fasting". Retrieved 2012-11-26. 
  3. ^ a b Johnson, James B.; Laub, Donald R.; John, Sujit (2006). "The effect on health of alternate day calorie restriction: Eating less and more than needed on alternate days prolongs life". Medical Hypotheses 67 (2): 209–11. doi:10.1016/j.mehy.2006.01.030. PMID 16529878. 
  4. ^ a b Antoni, Rona; Johnston, Kelly L.; Collins, Adam L.; Robertson, M. Denise (2014). "The Effects of Intermittent Energy Restriction on Indices of Cardiometabolic Health" 2014. 
  5. ^ Stote, KS; Baer, DJ; Spears, K; Paul, DR; Harris, GK; Rumpler, WV; Strycula, P; Najjar, SS; et al. (2007). "A controlled trial of reduced meal frequency without caloric restriction in healthy, normal-weight, middle-aged adults" (PDF). The American journal of clinical nutrition 85 (4): 981–8. PMC 2645638. PMID 17413096. 
  6. ^ Mosley, Michael. "Eat, Fast and Live Longer". BBC. Retrieved 27 October 2013. 
  7. ^ "Eat, Fast and Live Longer with Michael Mosley". PBS. 3 April 2013. 
  8. ^ Mattson, MP (February 4, 2014). "Fasting: molecular mechanisms and clinical applications". Cell Metabolism 19 (1932-7420): 181–92. doi:10.1016/j.cmet.2013.12.008. PMID 24440038. Retrieved 10 May 2015. 
  9. ^ Carlson, AJ; Hoelzel, F (1946). "Apparent prolongation of the life span of rats by intermittent fasting" (PDF). The Journal of nutrition 31: 363–75. PMID 21021020. 
  10. ^ Mattson, M; Wan, R (March 2005). "Beneficial effects of intermittent fasting and caloric restriction on the cardiovascular and cerebrovascular systems". J Nutr Biochem. 2005 Mar;16(3): 16 (3): 129–37. doi:10.1016/j.jnutbio.2004.12.007. PMID 15741046. 
  11. ^ Anson, R. Michael; Guo, Zhihong; de Cabo, Rafael; Iyun, Titilola; Rios, Michelle; Hagepanos, Adrienne; Ingram, Donald K.; Lane, Mark A.; Mattson, Mark P. (2003). "Intermittent fasting dissociates beneficial effects of dietary restriction on glucose metabolism and neuronal resistance to injury from calorie intake". Proceedings of the National Academy of Sciences 100 (10): 6216–20. Bibcode:2003PNAS..100.6216A. doi:10.1073/pnas.1035720100. JSTOR 3147568. PMC 156352. PMID 12724520. 
  12. ^ Wan, R; Camandola, S; Mattson, MP (2003). "Intermittent food deprivation improves cardiovascular and neuroendocrine responses to stress in rats". The Journal of nutrition 133 (6): 1921–9. PMID 12771340. 
  13. ^ Mattson, Mark P. (2008). "Dietary factors, hormesis and health". Ageing Research Reviews 7 (1): 43–8. doi:10.1016/j.arr.2007.08.004. PMC 2253665. PMID 17913594. 
  14. ^ Varady, KA; Hellerstein, MK (2007). "Alternate-day fasting and chronic disease prevention: A review of human and animal trials". The American journal of clinical nutrition 86 (1): 7–13. PMID 17616757. 
  15. ^ Alirezaei, Mehrdad; Kemball, Christopher C; Flynn, Claudia T; Wood, Malcolm R; Whitton, J. Lindsay; Kiosses, William B (2010). "Short-term fasting induces profound neuronal autophagy". Autophagy 6 (6): 702–710. doi:10.4161/auto.6.6.12376. PMC 3106288. PMID 20534972. 
  16. ^ "Food restriction by intermittent fasting induces diabetes and obesity and aggravates spontaneous atherosclerosis development in hypercholesterolaemic mice.". Br J Nutr 111 (6): 979–86. Mar 2014. doi:10.1017/S0007114513003383. PMID 24176004. 
  17. ^ Heilbronn, Leonie K; Smith, Steven R; Martin, Corby K; Anton, Stephen D; Ravussin, Eric (2005). "Alternate-day fasting in nonobese subjects: Effects on body weight, body composition, and energy metabolism". The American Journal of Clinical Nutrition 81 (1): 69–73. PMID 15640462. 
  18. ^ Klempel, Monica C.; Kroeger, Cynthia M.; Varady, Krista A. (2013). "Alternate day fasting (ADF) with a high-fat diet produces similar weight loss and cardio-protection as ADF with a low-fat diet". Metabolism 62 (1): 137–43. doi:10.1016/j.metabol.2012.07.002. PMID 22889512. 
  19. ^ "Hugh Jackman's Intermittent Fasting for Wolverine". Men's Fitness. 

Further reading[edit]