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Friday, 19 July 2013

Intermittent Fasting and Longevity

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.

Insulin-like growth factor is produced in the liver and released according to activity of Human Growth Hormone (HGH), produced in the pituitary gland. Levels of both naturally decline with age, which is desirable: high levels of IGF-1 encourage the body to focus on producing new cells rather than existing repairing ones. As cellular and DNA damage continues to go unchecked, aging and disease take hold. What's more, cancerous cells usually mutate to take advantage of both insulin and IGF-1, using them as fuel. The reverse is also true: in mice genetically engineered to have low levels of IGF-1, lifespan increases to the human equivalent of 120 years, and among the few hundred people worldwide with low IGF-1, cancer and diabetes are virtually unknown.

In the recent BBC documentary "Eat, Fast and Live Longer," Michael Mosley fasted for three days and four nights. The result? Halved levels of IGF-1, slashing his risk for age-related disease. His blood glucose levels also fell, indicating improved sensitivity to insulin and lessened risk of developing diabetes. As is typical, after returning to his normal diet Mosley's IGF-1 levels rose to what they were before. To maintain lower levels of the hormone, Mosley adopted the practice of intermittent fasting, taking up what is known as the 5:2 diet. Followers of the 5:2 diet eat whatever they want five days a week and about 500 calories twice a week. Amazingly, following this simple formula is known to lower blood pressure, HDL cholesterol and blood lipids and sustain weight loss no matter what kind of food is consumed. After five weeks on the diet, Mosley lost almost 15 pounds.

Additional promising research on mice suggests that intermittent fasting protects against mental illnesses including Alzheimer's, Parkinson's and dementia.

Two simpler dietary interventions also promise some dampening of IGF-1: lowering protein intake, which for most people is higher than is optimal, and refraining from milk. Hormone-rich milk contains an abundance of IGF-1 and is known to contribute to the risk of cancer, particularly fatal prostate cancer.

Microarray analyses identify fasting-regulated genes involved in IF-induced longevity
a, The sampling scheme is shown. b, d, Expression profiles of fasting-induced up-regulated (b, left) and down-regulated (d) genes. Average expression profiles are shown (b, right, see text). c, Scatter plots of the expression levels for TOR (let-363) RNAi-fasting (top left) or rheb-1 RNAi-fasting (top right) worms. The black and blue lines indicate the diagonal and twofold changes between two samples. Venn diagram of fasting-induced 112 genes (bottom). e, Quantitative PCR with reverse transcription (qRT–PCR) of ins-7 expression. f, HSP-12.6, a downstream target of DAF-16, functions to mediate IF-induced longevity.

  1. 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. 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. 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. en.wikipedia.org/wiki/Intermittent_fasting#cite_note-pmid12724520-1
  6. http://www.naturalnews.com/037474_intermittent_fasting_longevity_igf-1.html

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