# The health benefits of fasting **URL:** \ **Category:** Factual Questions\ **Created:** [May 13, 2009, 11:45am UTC](https://boards.straightdope.com/t/the-health-benefits-of-fasting/496270 "2009-05-13T11:45:37Z")\ **Posts on this page:** 16\ **Page:** 1
**Author:** ![Mojo\_Pin](https://avatars.discourse-cdn.com/v4/letter/m/6a8cbe/32.png) [@Mojo\_Pin](https://boards.straightdope.com/u/Mojo_Pin)\ **Post date:** [May 13, 2009, 11:45am UTC](https://boards.straightdope.com/t/the-health-benefits-of-fasting/496270/1 "2009-05-13T11:45:37Z")
Fasting has a whole lot of religious/spiritual baggage, which I have no interest in. Nor do I care at all about losing weight. That said, I recently ran across [this](http://serendip.brynmawr.edu/exchange/node/1834) short paper on the internet, which piqued my interest. To a total layman, much of the stuff that is said sounds believable, probable even, and the whole thing is very attractive. But the paper is 7 years old, and none of the linked sources work anymore. Most everything else I could find on the internet was of the aforementioned religious/anorexic sort of discussion, though I did find one other [article](http://www.menshealth.com/bestfoods/food_features/The_Worlds_Most_Effective_Diet.php) which says pretty much the same thing as the other one (with no cites), this time drawing from his personal experience as a food lover who fasts for 36 hours weekly in order to enjoy the other meals that much more. So the question I put to the dope is: how much science is there behind this statement “The only reliable way to extend the lifespan of a mammal is under-nutrition without malnutrition.”, as well as the numerous other claimed benefits of fasting for a short duration regularly. Bonus question: is there a web resource other than public forums where reliable (and properly backed up) information regarding health & fitness can be found? p.s. I’ve gone ahead and started my first trial fast, and right now am into my 26th hour, probably the longest I’ve gone without food since I was born. It’s not bad (I’m about as hungry now as I am when I eat dinner a couple hours late). I did have a mild headache that lasted \<30 minutes a couple hours ago, and I’m getting some white residue on my tongue that I’ve been spitting out. ---
**Author:** ![Philster](https://avatars.discourse-cdn.com/v4/letter/p/13edae/32.png) [@Philster](https://boards.straightdope.com/u/Philster)\ **Post date:** [May 13, 2009, 12:39pm UTC](https://boards.straightdope.com/t/the-health-benefits-of-fasting/496270/2 "2009-05-13T12:39:16Z")
Tip: Search under ‘calorie restriction’ and ‘fasting’ for more accurate results. You will find some good data, but the real, well-done studies on **fasting** are usually conducted by folks who have been studying (rather well) the effects of **calorie restriction** on health and longevity. Some good science and double-blind studies to be found. Dr. Ray Walford (sp?) at UCLA was a pioneer. ---
**Author:** ![lazybratsche](https://avatars.discourse-cdn.com/v4/letter/l/ba8739/32.png) [@lazybratsche](https://boards.straightdope.com/u/lazybratsche)\ **Post date:** [May 13, 2009, 1:29pm UTC](https://boards.straightdope.com/t/the-health-benefits-of-fasting/496270/3 "2009-05-13T13:29:01Z")
There’s less concrete data for humans, but it looks like the effects of caloric restriction will be similar to those seen in every other model organism studied so far. So far the studies for humans mostly say that caloric restriction will help improve certain measures of health, but there isn’t any data about the longevity effects yet. In mice, there’s a ~30% life span increase from caloric restriction (feeding them ~1/2 what they would usually eat). I think that intermittent fasting (feeding them as much as they want, every other day) gives a similar extension, though I don’t have a cite for that off the top of my head. ---
**Author:** ![Surreal](https://avatars.discourse-cdn.com/v4/letter/s/eada6e/32.png) [@Surreal](https://boards.straightdope.com/u/Surreal)\ **Post date:** [August 31, 2012, 3:16pm UTC](https://boards.straightdope.com/t/the-health-benefits-of-fasting/496270/4 "2012-08-31T15:16:31Z")
> [@Mojo\_Pin](#): > > So the question I put to the dope is: how much science is there behind this statement “The only reliable way to extend the lifespan of a mammal is under-nutrition without malnutrition.” Caloric restriction does not appear to extend lifespan in primates: [http://www.nature.com/news/calorie-restriction-falters-in-the-long-run-1.11297](http://www.nature.com/news/calorie-restriction-falters-in-the-long-run-1.11297) > [@](#): > > The verdict, from a 25-year study in rhesus monkeys fed 30% less than control animals, represents another setback for the notion that a simple, diet-triggered switch can slow ageing. Instead, the findings, published this week in Nature1, suggest that genetics and dietary composition matter more for longevity than a simple calorie count. Previous studies in primates found that caloric restriction extended lifespan, but these studies were garbage. Some of these studies fed the animals nearly 30% of calories from sugar. > [@](#): > > One reason for that difference could be that the WNPRC monkeys were fed an unhealthy diet, which made the calorie-restricted monkeys seem healthier by comparison simply because they ate less of it. The WNPRC monkeys’ diets contained 28.5% sucrose, compared with 3.9% sucrose at the NIA. ---
**Author:** ![Surreal](https://avatars.discourse-cdn.com/v4/letter/s/eada6e/32.png) [@Surreal](https://boards.straightdope.com/u/Surreal)\ **Post date:** [August 31, 2012, 4:23pm UTC](https://boards.straightdope.com/t/the-health-benefits-of-fasting/496270/5 "2012-08-31T16:23:06Z")
Apparently there’s been massive publication bias in caloric restriction research as well. Here’s a recent rodent study that found that CR might actually do more harm than good: [http://onlinelibrary.wiley.com/doi/10.1111/j.1474-9726.2009.00533.x/pdf](http://onlinelibrary.wiley.com/doi/10.1111/j.1474-9726.2009.00533.x/pdf) > [@](#): > > Chronic dietary restriction (DR) is considered among the most robust life-extending interventions, but several reports indicate that DR does not always extend and may even shorten lifespan in some genotypes. An unbiased genetic screen of the lifespan response to DR has been lacking. Here, we measured the effect of one commonly used level of DR (40% reduction in food intake) on mean lifespan of virgin males and females in 41 recombinant inbred strains of mice. Mean strain-specific lifespan varied two to threefold under ad libitum (AL) feeding and 6- to 10-fold under DR, in males and females respectively. **Notably, DR shortened lifespan in more strains than those in which it lengthened life**. ---
**Author:** ![DSeid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dseid/32/20194_2.png) [@DSeid](https://boards.straightdope.com/u/DSeid)\ **Post date:** [September 1, 2012, 12:28pm UTC](https://boards.straightdope.com/t/the-health-benefits-of-fasting/496270/6 "2012-09-01T12:28:32Z")
Also see [this WSJ article](http://online.wsj.com/article/SB10000872396390444772804577619394017185860.html) that places that new calorie restriction (CR) study in a more understandable broader context. It’s a big deal study but may not be enough to be the end of the story. My pre-existing bias was to be very skeptical of the calorie restriction work but it still does seem that the results of calorie restriction depend on what gets defined as “control” and on the individual populations studied. The possibility remains open that humans are different than baboons or that the response to CR will be different based on individual subpopulation factors be they genetic, baseline diet related, microbiome related, some combination, or other. I suspect the concept aint dead yet. It is also a _different_ (albeit related) concept than the intermittent fasting (IF) one that the op had been talking about. IF does not require total calorie reduction/restriction. In most studies versions total calorie intake over time may be the same. People eat once a day or fast, either completely or with substantially decreased calories, one day and then eat all they feel like the next. Many woo claims are made about it (such as in the op’s link for that “detoxification” bit) and there are a few studies that give a hint of a suggestion of some potential benefits for some people. [See here](http://ajcn.nutrition.org/content/90/5/1138.full) for an example of an alternate day fasting approach: > [@](#): > > To date, 3 ADF studies in humans have been performed (5–7). Results from the 2 trials performed in normal-weight men and women indicate that 2–3 wk of ADF (complete fast on the fast day) significantly lowered body weight by 2.5% from baseline (5, 6). Decreases in triacylglycerol concentrations and increases in HDL-cholesterol concentrations were also observed (5, 6). Findings from the third trial conducted in overweight adults showed that 8 wk of modified ADF (20% restriction on the fast day) significantly lowered body weight by ≈8% from baseline (7). This trial also showed LDL-cholesterol and triacylglycerol reductions of 10% and 40%, respectively, when posttreatment values were compared with baseline (7). Whether or not these weight loss and cardioprotective effects can be reproduced in obese individuals by using ADF remains unknown. … > > … we show here that an ADF regimen, which allowed participants to consume 25% of their energy needs on the fast day, resulted in a mean weight loss of 5.8% from baseline after only 8 wk of treatment. Decreases in several key biomarkers for CAD risk, such as total cholesterol, LDL cholesterol, triacylglycerols, systolic blood pressure, and heart rate, were also observed. Additionally, we show here that a similar rate of weight loss was achieved during the ADF controlled food intake period when compared with the ADF self-selected food intake period. These data suggest that subjects were able to maintain the ADF meal pattern when preparing their own meals at home (ie, when removed from a clinically controlled environment). … Not much to go on. Again, the results may actually depend on the details. What is the timing of the intake for example? There is a fairly large body of work now that demonstrates the consequences to shift workers from eating at night and that the same number of calories eaten have different metabolic effects if consumed in different pattens. (See [this old post](http://boards.straightdope.com/sdmb/showpost.php?p=14341150&postcount=6) for some references and additional information.) I remain very skeptical about IF (am if anything biased to belief that “grazing” during daytime hours is more likely helpful) but I will also remain open to the possibility that some version of it may have some benefits that may be a preferred nutrition approach for some individual temperaments. ---
**Author:** ![benbo1](https://avatars.discourse-cdn.com/v4/letter/b/e19adc/32.png) [@benbo1](https://boards.straightdope.com/u/benbo1)\ **Post date:** [September 2, 2012, 10:19am UTC](https://boards.straightdope.com/t/the-health-benefits-of-fasting/496270/7 "2012-09-02T10:19:55Z")
From what I’ve been researching, it all boils down to telomeres - the protective caps on nerve endings. Shortened telomeres ----\> acclerated aging. The theory for years was that a low-calorie diet put the body into starvation mode, which protected the telomeres. I take resveratrol pills (extract of the good stuff in red wine), and the accompanying pamphlet makes the claim that their formula stimulates the sirulin gene, which mimics the starvation effect - with the added bonus of not having to starve yourself. Interestingly, in the period I’ve been taking it with the same diet, my blood sugar has gone down, HDL up, and HDL/LDL ratio bigger. Of course, this ain’t solid proof. As more time goes by, and we have a bigger population of people taking resveratrol, we can have better studies. As an aside, it’s observed in families of Holocaust survivors that they, who typically were starving from years in the camps, often live longer-than-average lives providing they avoid the usual killers (diabetes, heart attack, stroke, etc.). I’d be interested if there are studies of the non-European starvation victims (China? Ethiopia?) to see if this is a cross-cultural phenom. ---
**Author:** ![DSeid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dseid/32/20194_2.png) [@DSeid](https://boards.straightdope.com/u/DSeid)\ **Post date:** [September 2, 2012, 2:36pm UTC](https://boards.straightdope.com/t/the-health-benefits-of-fasting/496270/8 "2012-09-02T14:36:51Z")
**benbo1** , there may (or may not) indeed be benefits to resveratrol, but that accompanying pamphlet is a whole hooha of woo … it takes a few speculative and somewhat questionable bits and after presuming each is correct extrapolates and connects in pretty wild ways. 1. Telomeres are on chromosomes not nerve endings. 2. [The telomere hypothesis of aging](http://mcb.berkeley.edu/courses/mcb135k/telomeres.html) has very little to support . 3. The connection between [sirtuin and longevity](http://www.nytimes.com/2011/09/22/science/22longevity.html?_r=1) is questionable even in the yeast, fruit fly, and roundworm models that it was allegedly demonstrated in. 4. The connection between resveratrol and sirtuin is still sketchy; connecting it to any level achievable by supplementation is sketchier yet. 5. As noted by **surreal** the conclusion that calorie restriction can result in greater longevity was very premature. In some species yes and in others it shortens lifespans, in about equal numbers. 6. I have no knowledge of that bit about Holocaust survivors but it would be in keeping with calorie restriction work in monkeys that was initially positive. Overall there was no difference in lifespan, only when the usual causes of death were taken out from analysis. ---
**Author:** ![Learjeff](https://avatars.discourse-cdn.com/v4/letter/l/94ad74/32.png) [@Learjeff](https://boards.straightdope.com/u/Learjeff)\ **Post date:** [September 2, 2012, 5:36pm UTC](https://boards.straightdope.com/t/the-health-benefits-of-fasting/496270/9 "2012-09-02T17:36:37Z")
In [Power, Sex, and Suicide](http://www.nick-lane.net/Power,%20Sex,%20Suicide.html), Nick Lane advances the theory that the link between low-calorie diets and longevity can be explained by properties of mitochondria, the organelles in cells that provide energy for the cell’s activities. It goes something like this. Free radicals (loose protons) cause damage to the cell. (\*) They’re emitted by mitochnondria, when the mitochondria has an excess of fuel and low demand for energy. Increase the energy demand, or reduce the surplus fuel supply, and the rate of proton leakage is reduced. It’a a very interesting book, and this is just one of the topics it covers. (\*) This is the theory behind the idea that consuming antioxidants is helpful. Decreasing the oxidation state of cells would help to slurp up the free radicals. However, there is little or no clinical evidence that consuming antioxidants has any effect, and there’s very good evidence that cells control and maintain a normal oxidation state regardless of what we consume. In any case, there’s a huge difference to periodic fasting and a steady low caloric intake. There may be benefits to fasting, but I doubt that they’d be related to the above, unless fasting periods are daily rather than monthly. ---
**Author:** ![panaccione](https://avatars.discourse-cdn.com/v4/letter/p/94ad74/32.png) [@panaccione](https://boards.straightdope.com/u/panaccione)\ **Post date:** [September 2, 2012, 7:53pm UTC](https://boards.straightdope.com/t/the-health-benefits-of-fasting/496270/10 "2012-09-02T19:53:19Z")
[This guy does it.](http://fit2fat2fit.com/) He’s pretty popular. ---
**Author:** ![al27052](https://avatars.discourse-cdn.com/v4/letter/a/41988e/32.png) [@al27052](https://boards.straightdope.com/u/al27052)\ **Post date:** [September 3, 2012, 1:11am UTC](https://boards.straightdope.com/t/the-health-benefits-of-fasting/496270/11 "2012-09-03T01:11:04Z")
I’ve definitely done a lot of short-term fasts, up to 4 days at a time, and several dozen 2 and 3 day fasts. It will often reduce or temporarily eliminate certain annoying health problems, but they usually come back when you start eating again. Still, it can be nice to be temporarily rid of them. Most fasting experts will recommend continuing the fast until the white stuff stops appearing on your tongue in the morning. This is a sign that your body is “cleaned out”, so to speak. It’s very important to break the fast with something watery, like watery fruit, fruit juice, etc… You don’t ever want to break a fast with something dry, like crackers. ---
**Author:** ![Leo\_Bloom](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leo_bloom/32/10377_2.png) [@Leo\_Bloom](https://boards.straightdope.com/u/Leo_Bloom)\ **Post date:** [September 3, 2012, 2:09am UTC](https://boards.straightdope.com/t/the-health-benefits-of-fasting/496270/12 "2012-09-03T02:09:09Z")
> [@DSeid](#): > > …p.s. I’ve gone ahead and started my first trial fast, and right now am into my 26th hour, probably the longest I’ve gone without food since I was born. It’s not bad (I’m about as hungry now as I am when I eat dinner a couple hours late). I did have a mild headache that lasted \<30 minutes a couple hours ago, and I’m getting some white residue on my tongue that I’ve been spitting out. I know exactly how you feel. Throw in standing up and sitting down constantly, and, if you want, wailing, you could always convert to Reconstructionist Judaism and do that twice a year, and quite comfortably have your choice (fasting) integrated in a non-theistic atmosphere… I’m sorry to have bring this up in my double reply, but that’s the way it goes– > [@benbo1](#): > > As an aside, it’s observed in families of Holocaust survivors that they, who typically were starving from years in the camps, often live longer-than-average lives providing they avoid the usual killers (diabetes, heart attack, stroke, etc.)… Cite? ---
**Author:** ![Jackmannii](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jackmannii/32/311_2.png) [@Jackmannii](https://boards.straightdope.com/u/Jackmannii)\ **Post date:** [September 3, 2012, 2:15am UTC](https://boards.straightdope.com/t/the-health-benefits-of-fasting/496270/13 "2012-09-03T02:15:11Z")
> [@al27052](#): > > Most fasting experts will recommend continuing the fast until the white stuff stops appearing on your tongue in the morning. This is a sign that your body is “cleaned out”, so to speak. Personally, I wait until the water in the toilet is no longer black when I pee. ---
**Author:** ![al27052](https://avatars.discourse-cdn.com/v4/letter/a/41988e/32.png) [@al27052](https://boards.straightdope.com/u/al27052)\ **Post date:** [September 3, 2012, 2:18am UTC](https://boards.straightdope.com/t/the-health-benefits-of-fasting/496270/14 "2012-09-03T02:18:17Z")
> [@Jackmannii](#): > > Personally, I wait until the water in the toilet is no longer black when I pee. Was that supposed to be funny? I can’t tell. ---
**Author:** ![Michael63129](https://avatars.discourse-cdn.com/v4/letter/m/3da27b/32.png) [@Michael63129](https://boards.straightdope.com/u/Michael63129)\ **Post date:** [September 3, 2012, 3:06am UTC](https://boards.straightdope.com/t/the-health-benefits-of-fasting/496270/15 "2012-09-03T03:06:02Z")
If [this study](http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1071721/) is any indication, the longevity effects of caloric restriction are related more to a smaller body size and slower growth than anything to do with calories themselves (this also explains why women live longer - but only when men are taller on average). ---
**Author:** ![DSeid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dseid/32/20194_2.png) [@DSeid](https://boards.straightdope.com/u/DSeid)\ **Post date:** [September 3, 2012, 3:48am UTC](https://boards.straightdope.com/t/the-health-benefits-of-fasting/496270/16 "2012-09-03T03:48:35Z")
**Leo Bloom** , Mind telling me why you are attributing that quote to me? That was the op **Mojo Pin**. Mind you I fast every year, water only for about 24 hours, as a religious/cultural/spiritual tradition. My issue is my desperate need for coffee. I break the fast at the coffee pot. Never a white residue. And **al27052** I thought it was funny.