Intermittent fasting

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]

Contents

Studies

Animal studies

The 1945 study by Carlson and Hoelzel, referenced above, found that the apparent life span of rats in the study was increased by intermittent fasting. Tests in which a group of thirty-three rats were allowed the same food ad libitum and groups of thirty-seven, thirty-seven and thirty rats were fasted 1 day in 4, 3 and 2, respectively, after the age of 42 days, showed that the optimum amount of fasting appeared to be fasting 1 day in 3 and this increased the life span of littermate males about 20% and littermate females about 15%. However, the pre-experimental condition of the individual rats was also found to be an important factor determining the life spans. No drastic retardation of growth was produced by the intermittent fasting but the development of mammary tumors was retarded in proportion to the amount of fasting.[1]

A number of subsequent studies have shown beneficial effects of IF in animals.

Human studies

Similarly, studies on humans suggest similar beneficial results.

In the early 1960s, one study of fasting as a method of weight control noted that "[W]e have noticed an improvement in the last few months in the ability of these patients to keep their weight under control by observing one fast per week [water only]. This allows them to be more liberal with their diet on the other days. I cannot overemphasize the fact that they prefer this to perpetual daily denial with no alternative."[9]

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 regimen may provide many of the benefits of IF.[16]

See also

Notes

  1. ^ a b 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. doi:10.1073/pnas.1035720100 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. ^ 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.
  5. ^ 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.
  6. ^ 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.
  7. ^ 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.
  8. ^ 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.
  9. ^ Duncan GG. INTERMITTENT FASTS IN THE CORRECTION AND CONTROL OF INTRACTABLE OBESITY Trans Am Clin Climatol Assoc. 1962;74:121-9. PMID 14047310.
  10. ^ Bhutani S, Klempel MC, Berger RA, Varady KA. Improvements in Coronary Heart Disease Risk Indicators by Alternate-Day Fasting Involve Adipose Tissue Modulations. Obesity (Silver Spring). 2010 Mar 18. PMID 20300080.
  11. ^ 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.
  12. ^ 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.
  13. ^ 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.
  14. ^ Hayes DP. Nutritional hormesis. Eur J Clin Nutr. 2007 Feb;61(2):147-59. PMID 16885926.
  15. ^ Mattson MP. Dietary factors, hormesis and health. Ageing Res Rev. 2008 Jan;7(1):43-8. doi:10.1016/j.arr.2007.08.004 PMID 17913594.
  16. ^ 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. doi:10.1016/j.mehy.2006.01.030 PMID 16529878.

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