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 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 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.
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.
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.
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.
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:
Also see this WSJ article 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 for an example of an alternate day fasting approach:
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 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.
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.
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.
The connection between sirtuin and longevity is questionable even in the yeast, fruit fly, and roundworm models that it was allegedly demonstrated in.
The connection between resveratrol and sirtuin is still sketchy; connecting it to any level achievable by supplementation is sketchier yet.
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.
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.
In Power, Sex, and Suicide, 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.
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.
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–
If this study 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).
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.