Intermittent fasting

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Intermittent fasting (IF) is a pattern of eating that alternates between periods of fasting (usually meaning consumption of water and sometimes low-calorie drinks such as black coffee) and non-fasting.

There is evidence suggesting 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 fasting or due to an (often) concomitant overall decrease in calories, but recent studies have shown support for the former.[1][2] Alternate-day calorie restriction may prolong life span.[3] Intermittent fasting and caloric restriction 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.[4]

A specific form of intermittent fasting is alternate day fasting (ADF), also referred to as every other day fasting (EOD), or every other day feeding (EODF), a 48-hour routine typically composed of a 24-hour fast followed by a 24-hour non-fasting period.

Contents

Studies [edit]

Several formal and informal studies since the 1930s are discussed in a 2013 Scientific American article[5]. The effects of fasting in general, and in diabetes and on the brain were discussed in New Scientist in 2013[6].

Animal studies [edit]

The 1945 study by Carlson and Hoelzel, cited above, found that the apparent life span of rats in the study was increased by intermittent fasting. Tests in which a group of 33 rats were allowed the same food ad libitum and groups of 37, 37, and 30 rats were fasted one day in four, three, and two days, respectively, after the age of 42 days, showed that the optimum amount of fasting appeared to be fasting one day in three; this increased the life span of littermate males by about 20% and littermate females by about 15%. However, the pre-experimental condition of the individual rats was also found to be an important factor in 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.[4]

A number of subsequent studies have shown beneficial effects of intermittent fasting in animals:

  • "Reduced serum glucose and insulin levels and increased resistance of neurons in the brain to excitotoxic stress."[1]
  • Intermittent fasting was found to "Enhance cardiovascular and brain functions and improve 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."[7]
  • It may "ameliorate age-related deficits in cognitive function" in mice.[8]
  • A correlation between intermittent fasting and significantly improved biochemical parameters associated with the development of diabetic nephropathy.[9]
  • Resistance in mice to the effects of gamma irradiation.[10]
  • Lifespan increases of 40.4% and 56.6% in C. elegans for alternate day (24-hour) and every second day (48-hour) fasting, respectively, as compared to an ad libitum diet.[11]
  • Rats showed markedly improved long-term survival after chronic heart failure via pro-angiogenic, anti-apoptotic, and anti-remodeling effects.[12]
  • "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."[13]

But negative effects of intermittent fasting in animals have also been noted:

  • ADF in rats "prolongs life span and promotes numerous health benefits in rodents, including tissue protection from ischemic damage" but also has negative effects including causing "myocardial hypotrophy, cardiac fibrosis, diastolic dysfunction, and a reduction of cardiac reserve."[14]

Human studies [edit]

Studies on humans suggest possible benefits:

  • Intermittent fasting may function as a form of nutritional hormesis.[15]
  • Alternate-day fasting may encourage fat-oxidation.[16]
  • 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.[17]

Human diet [edit]

A number of individuals are experimenting with different varieties of intermittent fasting as a dietary regimen. 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. For example, "Fast-5" is a book promoting a regimen equivalent to "19/5". Other alternatives include "16/8" and "15/9".

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

In common usage, intermittent fasting describes any diet that includes a period of fasting and a period of non-fasting, even if the diet involves consuming a limited amount of calorie-containing beverages such as coffee or tea during the fasting period.[18] This contrasts with scientific usage of the term, in which no calories are consumed during the fasting period.

Another variation on intermittent fasting 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 intermittent fasting.[3]

Another possibility is eating only one meal per day without caloric restriction. When overall calorie intake is not reduced, this diet worsens some cardiovascular disease risk factors.[19]

The BBC2 Horizon documentary Eat, Fast & Live Longer showed another plan: during days of fasting, people eat 400-500 kcal (women) or 500-600 kcal (men), and during feed days, the diet was unrestricted. This was done either alternately (one day fasting, one day feeding) or by fasting two days per week: the 5:2 diet.[20]

References [edit]

  1. ^ a b Anson, R. Michael; Guo, Zhihong; de Cabo, Rafael; Iyun, Titilola; Rios, Michelle; Hagepanos, Adrienne; Ingram, Donald K.; Lane, Mark A. et al. (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. 
  2. ^ 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. 
  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 Carlson, AJ; Hoelzel, F (1946). "Apparent prolongation of the life span of rats by intermittent fasting". The Journal of nutrition 31: 363–75. PMID 21021020. 
  5. ^ David Stipp: How Intermittent Fasting Might Help You Live a Longer and Healthier Life, Scientific American, 17 January 2013
  6. ^ Emma Young, Hunger games: The new science of fasting, New Scientist, 2 January 2013
  7. ^ Mattson, M; Wan, R (2005). "Beneficial effects of intermittent fasting and caloric restriction on the cardiovascular and cerebrovascular systems". The Journal of Nutritional Biochemistry 16 (3): 129–37. doi:10.1016/j.jnutbio.2004.12.007. PMID 15741046. 
  8. ^ Halagappa, Veerendra Kumar Madala; Guo, Zhihong; Pearson, Michelle; Matsuoka, Yasuji; Cutler, Roy G.; Laferla, Frank M.; Mattson, Mark P. (2007). "Intermittent fasting and caloric restriction ameliorate age-related behavioral deficits in the triple-transgenic mouse model of Alzheimer's disease". Neurobiology of Disease 26 (1): 212–20. doi:10.1016/j.nbd.2006.12.019. PMID 17306982. 
  9. ^ Tikoo, Kulbhushan; Tripathi, Durga Nand; Kabra, Dhiraj G.; Sharma, Vikram; Gaikwad, Anil Bhanudas (2007). "Intermittent fasting prevents the progression of type I diabetic nephropathy in rats and changes the expression of Sir2 and p53". FEBS Letters 581 (5): 1071–8. doi:10.1016/j.febslet.2007.02.006. PMID 17316625. 
  10. ^ Kozubík, A; Pospísil, M (1982). "Protective effect of intermittent fasting on the mortality of gamma-irradiated mice". Strahlentherapie 158 (12): 734–8. PMID 6761903. 
  11. ^ Honjoh, Sakiko; Yamamoto, Takuya; Uno, Masaharu; Nishida, Eisuke (2008). "Signalling through RHEB-1 mediates intermittent fasting-induced longevity in C. Elegans". Nature 457 (7230): 726–30. doi:10.1038/nature07583. PMID 19079239. 
  12. ^ Katare, Rajesh G.; Kakinuma, Yoshihiko; Arikawa, Mikihiko; Yamasaki, Fumiyasu; Sato, Takayuki (2009). "Chronic intermittent fasting improves the survival following large myocardial ischemia by activation of BDNF/VEGF/PI3K signaling pathway". Journal of Molecular and Cellular Cardiology 46 (3): 405–12. doi:10.1016/j.yjmcc.2008.10.027. PMID 19059263. 
  13. ^ 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. 
  14. ^ Ahmet, Ismayil; Wan, Ruiqian; Mattson, Mark P.; Lakatta, Edward G.; Talan, Mark I. (2010). "Chronic Alternate-Day Fasting Results in Reduced Diastolic Compliance and Diminished Systolic Reserve in Rats". Journal of Cardiac Failure 16 (10): 843–53. doi:10.1016/j.cardfail.2010.05.007. PMC 2953475. PMID 20932467. 
  15. ^ 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. 
  16. ^ 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. 
  17. ^ 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. 
  18. ^ "An Introduction to Intermittent Fasting". Retrieved 2012-11-26. 
  19. ^ 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". The American journal of clinical nutrition 85 (4): 981–8. PMC 2645638. PMID 17413096. 
  20. ^ "Eat, Fast and Live Longer with Michael Mosley". PBS. April 3, 2013. 

External links [edit]

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