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Intermittent+Fasting - Libby McNiven Final Paper for NPB...

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Libby McNiven Final Paper for NPB 132 Fall 2009 P ART -T IME D IETING , F ULL -T IME B ENEFITS : T HE A DVANTAGES OF A LTERNATE D AY C ALORIC R ESTRICTION 1. Introduction “Restricting caloric intake to 60–70% of normal adult weight maintenance requirement prolongs lifespan 30–50% and confers near perfect health across a broad range of species” [1]. It’s a claim that seems too good to be true, yet there is ample evidence to back it up. The catch? It’s extremely difficult to comply voluntarily. Study animals subjected to such feeding and humans who have the willpower to consistently deny themselves can enjoy better health and longer life. But free-living animals and most people do not naturally restrict themselves. This paper will present evidence for a viable alternative to caloric restriction: alternate day caloric restriction. Evidence shows that the benefits of restricting energy intake every other day are nearly equal to that of daily caloric restriction, regardless of total caloric intake. Section 2 will give background information caloric restriction, and section 3 will present evidence for the benefits of IF on general markers of health (longevity, weight loss, lipid profiles, inflammation and oxidative stress) and benefits for specific systems and conditions (cognition, cardiovascular health and diabetes). 2. Background: Caloric Restriction Caloric restriction (CR) means consuming less energy than is required for maintenance over a specified time. Reducing intake by a small amount, say 5%, causes gradual weight loss and possibly general improvement in health. Further reductions of 20-40% produce profound health benefits. This paper will use CR to indicate the more severe degree of restriction: a daily energy intake of no more than 80% of one’s maintenance energy, over the course of weeks, months or years. The most widely touted benefit of CR is its ability to extend lifespan. It does this across species. Martin, Mattson et al cite studies from as far back as 1935 showing effects in rats, mice, fruitflies, nematodes, water fleas, spiders and fish [2]. In addition, CR appears to be the only treatment to extend lifespan across so many species. “The only environmental variable that has been shown to markedly affect the rate of aging in a wide range of species is caloric intake: Restricting food intake to a level below that which would be consumed voluntarily results in a decrease in the rate of aging and an increase in average and maximum life span” [3]. However, the mechanisms by which CR extends lifespan are unknown. At least part of the story includes an increase in healthspan, or delay in the onset of chronic disease. Individuals subjected to CR not only live to a ripe old age; they are remarkably healthy over the course of their very long lives. This, in turn, rests on how CR impacts myriad physiologic pathways. “A reduction in daily energy intake by 20% to 40% of baseline requirements has consistently resulted in the prolongation of average and maximal
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