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Intermittent fasting (IF) is a pattern of eating that alternates between periods of fasting (usually meaning consumption of water only) and non-fasting. A specific form of IF is alternate day fasting (ADF), which is a 48-hour routine typically composed of a 24-hour fast followed by a 24-hour non-fasting period. (ADF is also sometimes referred to as every other day (EOD) fasting, or sometimes every other day feeding (EODF).)

There is some evidence that intermittent fasting may have beneficial effects on the health and longevity of animals—including humans—that are similar to the effects of caloric restriction (CR). There is currently no consensus as to the degree to which this is simply due to an (often) concomitant overall decrease in calories. (IF and CR are forms of Dietary Restriction (DR), which is sometimes referred to as Dietary Energy Restriction (DER).)

Scientific study of intermittent fasting in rats (and anecdotally in humans) was carried out at least as early as 1943.^[1]

Possible medical benefits

A number of studies have shown beneficial effects of IF in animals, including:

• a study finding "reduced serum glucose and insulin levels and increased resistance of neurons in the brain to excitotoxic stress"^[2]

• a review of previous research that found that IF "enhance[s] cardiovascular and brain functions and improve[s] several risk factors for coronary artery disease and stroke including a reduction in blood pressure and increased insulin sensitivity" and that "cardiovascular stress adaptation is improved and heart rate variability is increased in rodents" and that "rodents maintained on an IF regimen exhibit increased resistance of heart and brain cells to ischemic injury in experimental models of myocardial infarction and stroke."^[3]

• a review of research on ADF and CR found 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"^[4]

• a study suggesting that IF may "ameliorate age-related deficits in cognitive function" in mice^[5]

• a study suggesting that IF significantly improves biochemical parameters associated with development of diabetic nephropathy^[6]

• a study showing that serum from humans following an IF diet had positive effects (reduced triglycerides in men and increased HDL in women, as well as reduced cell proliferation and increased heat resistance) in vitro on human hepatoma cells^[7]

• a study showing resistance in mice to the effects of gamma irradiation^[8]

• a 2008 study showing lifespan increases of 40.4% and 56.6% in C. elegans for alternate day (24 hour) and two-of-each-three day (48 hour) fasting, respectively, as compared to an ad libitum diet.^[9]

• a 2009 study on rats showed markedly improved long-term survival after chronic heart failure via pro-angiogenic, anti-apoptotic and anti-remodeling effects.^[10]

• a 2009 study suggests that IF confers protection from toxic chemotherapy treatments, allowing higher doses and therefore more effective treatment for cancers.^[11]

It is possible that IF may function as a form of nutritional hormesis.^[12][13]

As a human diet

A number of individuals are experimenting with different varieties of IF as a dietary regime. In this context, shorthand such as "20/4" is used to denote a repeating pattern of 20 hours of fasting followed by 4 hours of non-fasting. ("Fast-5" is the name of a book/regime equivalent to "19/5".)

The phase of the fasting period may also be specified. Practitioners often start the fasting period at the commencement of nightly sleep.

Unlike the use of IF in scientific experiments, in popular usage the term is sometimes also applied even when the "fasting" period involves consumption of some calorie-containing beverages.

Another variation on IF is to consume limited calories (e.g., 20% of normal) rather than none at all on "fasting" days. This regime may provide many of the benefits of IF.^[14]

See also

• Calorie restriction
• Fasting

Notes

1. ^ Anton J. Carlson and Frederick Hoelzel. Apparent Prolongation of the Life Span of Rats by Intermittent Fasting. Journal of Nutrition Vol. 31 No. 3 March 1946, pp. 363-375
2. ^ Anson RM, Guo Z, de Cabo R, Iyun T, Rios M, Hagepanos A, Ingram DK, Lane MA, Mattson MP. Intermittent fasting dissociates beneficial effects of dietary restriction on glucose metabolism and neuronal resistance to injury from calorie intake. Proc Natl Acad Sci U S A. 2003 May 13;100(10):6216-20. PMID 12724520.
3. ^ Mattson MP, Wan R. Beneficial effects of intermittent fasting and caloric restriction on the cardiovascular and cerebrovascular systems. J Nutr Biochem. 2005 Mar;16(3):129-37. PMID 15741046.
4. ^ Varady KA, Hellerstein MK. Alternate-day fasting and chronic disease prevention: a review of human and animal trials. Am J Clin Nutr. 2007 Jul;86(1):7-13. PMID 17616757.
5. ^ Halagappa VK, Guo Z, Pearson M, Matsuoka Y, Cutler RG, Laferla FM, Mattson MP. Intermittent fasting and caloric restriction ameliorate age-related behavioral deficits in the triple-transgenic mouse model of Alzheimer's disease. Neurobiol Dis. 2007 Apr;26(1):212-20. PMID 17306982.
6. ^ Tikoo K, Tripathi DN, Kabra DG, Sharma V, Gaikwad AB. Intermittent fasting prevents the progression of type I diabetic nephropathy in rats and changes the expression of Sir2 and p53. FEBS Lett. 2007 Mar 6;581(5):1071-8. PMID 17316625.
7. ^ Allard JS, Heilbronn LK, Smith C, Hunt ND, Ingram DK, et al. In Vitro Cellular Adaptations of Indicators of Longevity in Response to Treatment with Serum Collected from Humans on Calorie Restricted Diets. PLoS ONE 3(9): e3211 doi:10.1371/journal.pone.0003211 2008 PMID 18791640.
8. ^ Kozubík A, Pospísil M. Protective effect of intermittent fasting on the mortality of gamma-irradiated mice. Strahlentherapie. 1982 Dec;158(12):734-8. PMID 6761903.
9. ^ Honjoh S, Yamamoto T, Uno M, Nishida E. Signalling through RHEB-1 mediates intermittent fasting-induced longevity in C. elegans. Nature. 2008 Dec 14. PMID 19079239.
10. ^ Katare RG, Kakinuma Y, Arikawa M, Yamasaki F, Sato T. Chronic intermittent fasting improves the survival following large myocardial ischemia by activation of BDNF/VEGF/PI3K signaling pathway. J Mol Cell Cardiol. 2009 Mar;46(3):405-12. PMID 19059263.
11. ^ Johnson JB, John S, Laub DR. Pretreatment with alternate day modified fast will permit higher dose and frequency of cancer chemotherapy and better cure rates. Med Hypotheses. 2009 Apr;72(4):381-82. PMID 19135806.
12. ^ Hayes DP. Nutritional hormesis. Eur J Clin Nutr. 2007 Feb;61(2):147-59. PMID 16885926.
13. ^ Mattson MP. Dietary factors, hormesis and health. Ageing Res Rev. 2008 Jan;7(1):43-8. PMID 17913594.
14. ^ Johnson JB, Laub DR, John S. The effect on health of alternate day calorie restriction: eating less and more than needed on alternate days prolongs life. Med Hypotheses 2006;67(2):209-11. PMID 16529878.

External links

• Feast, fast and reduce risks, Susan Bowerman, Los Angeles Times, December 10, 2007.
• Eat Less, Live Longer?, Cheryl Simon Silver, Genome News Network, July 9, 2004.
• Fasting every other day, while cutting few calories, may reduce cancer risk, UC Newsroom, March 14, 2005.