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How Fasting Increases Lifespan | Mark’s Daily Apple

Posted: July 10, 2015 at 7:44 am

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A time-honored and research-tested way to extend an animals lifespan is to restrict its caloric intake. Studies repeatedly confirm that if, say, a lab mouse normally gets two full bowls of lab chow a day, limiting that mouse to one and a half bowls of lab chow a day will make that mouse live longer than the mouse eating the full two bowls.Cool, cool, a longer life is great and all, but what about the downsides of straight calorie restriction, aside from willfully restricting your food intake, ignoring hunger pangs, relegating yourself to feeling discontent with meals, and counting calories and macronutrients obsessively? Are there any others? Sure:

Loss of muscle mass. Humans undergoing calorie restriction often suffer loss of lean muscle mass and strength, all pretty objectively negative effects (unless you really go for the gaunt Christian Bale in The Machinist look and use a super-strong bionic exoskeleton for all your physical tasks).

Loss of bone mineral density. Humans who calorie restrict in studies also show signs of lower bone mineral density when compared to humans who lose weight from exercise,particularly in the hip and spine the two areas most susceptible to fall-related bone breaks. I wrote about this study some time ago here.

Oh, and theres the fact that the act of restricting ones calories can be mind-numbing, miserable, and difficult for a great many people, especially if its a lifelong pursuit. (Unless, of course, you eat according to the Primal Blueprint and are fat-adapted. It can make CR not only tolerable, but a cinch because we become so good at living off stored body fat. We dont suffer from sugar lows when we skip meals the way most people who fast do, but I digress.) Thats kind of a biggie.

What about fasting? In previous installments of this series, Ive explained how fasting can sometimes be described as a short cut to the benefits of calorie restriction, an easier (and even more effective) path to the same destination. Studies on fasting/calorie restriction and cancer find that fasting is more effective in a shorter amount of time (weeks or months versus mere days). Does the same hold true for longevity? Can fasting also extend lifespan without making us look like a calorie-restricted monkey?

1945 marks the first real study (PDF) of the effects of intermittent fasting on lifespan in animals. Beginning at day 42 of their lives, rats were either fasted one day in four, one day in three, or every other day. All fasted rats, save for the females who were fasted one day in four, lived longer than control rats on a normal schedule. Although females outlived males in general (like always), fasting had the greatest effect in males. Male rats did best on every other day fasting; female rats did best on one day in three fasting. Fasted rats weighed less than control rats, so they likely also ate less, even though feeding days were ad libitum.

In a 1982 study, mice fed every other day lived 82% longer than mice fed ad libitum every day. No word on calorie intake.

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How Fasting Increases Lifespan | Mark’s Daily Apple

Recommendation and review posted by G. Smith