Real Life Extension: Caloric Restriction or Intermittent Fasting? (Part 1) 50 Comments
Can you slow the sands of time? The research say yes… but what’s the best option? (Photo: Thomas Ellis)
Most people don’t want to die.
Since even before Ponce de Leon and his search for the fountain of youth, man has been on a quest to achieve immortality.
Some people think we’re getting closer. In recent years, caloric restriction (CR) has been demonstrated to increase lab rat lifespans more than 20%. “Intermittent fasting” (IF), a much lesser-known and more lifestyle-friendly alternative, has shown results that even surpass CR in some respects.
Following up on the popularity of his last post on this blog (The Science of Fat-Loss: Why a Calorie Isn’t Always a Calorie), Dr. Eades examines these two options and his personal experiments with both.
If you want to live longer, this two-part article is an excellent place to start for avoiding common mistakes, pain and wasted effort.
How would you like it if I told you there was a way to eat pretty much anything and everything you wanted to eat and still maintain your health? Or better yet, what if I told you that you could eat pretty much anything and everything you wanted and even improve your health? Would you be interested?…
There is a way to reduce blood sugar, improve insulin sensitivity, reduce blood pressure, increase HDL levels, get rid of diabetes, live a lot longer, and still be able to lose a little weight. All without giving up the foods you love. And without having to eat those foods in tiny amounts. Sounds like a late-night infomercial gimmick, but it isn’t.
When I wrote those words as the lede to an article about a year and a half ago, the idea of intermittent fasting was limited mainly to research scientists and faddists. But a number of studies had been published – primarily on rodents – showing that intermittent fasting led to a host of benefits that not even caloric restriction could claim.
And these weren’t studies published by no-name scientists laboring in backwater research departments. The lead author on many of these papers was Mark P. Mattson, Ph.D, the Chief of the Laboratory of Neurosciences and Chief of the Cellular and Molecular Neurosciences Section of the National Institute on Aging, a division of the National Institutes of Health. People were starting to take notice.
Before the work on intermittent fasting, the only real strategy for extending the lives of laboratory animals was caloric restriction (CR). If rats or mice or even primates had their calories restricted by 30-40 percent as compared to those fed ad libitum ["at pleasure" = as much as they want] they lived 20-30 percent longer. These studies are typically done by dividing genetically similar animals into two groups, then giving one group all the food it can eat in a day. Researchers measure the food consumed, then reduce it by 30-40 percent and give to the other group the next day. Each day this drill is repeated with the calorically restricted group getting a reduced amount of food compared to what the other group got the day before.
These CR verses ad libitum-fed studies almost uniformly demonstrate an increase in longevity in the CR animals. The CR animals not only live 30 percent or so longer, they don’t develop cancers, diabetes, heart disease, or obesity. And these animals have low blood sugar levels, low insulin levels, good insulin sensitivity, low blood pressure and are, in general, much healthier physically than their ad libitum fed counterparts. But not so psychologically.
As we saw in the Keys semi-starvation study, caloric restriction isn’t much fun for humans, and it apparently isn’t all that much fun for the animals undergoing it either. When rats live out their ratty lives calorically restricted in their cages, they seem to show signs of depression and irritability. Primates do as well. If primates don’t get enough cholesterol, they can actually become violent. But they do live longer. Even though CR has never been proven in humans, based on lab animal experience it does work. So, if you’re willing to put up with irritability, hostility and depression, it might be worth cutting your calories by 30 percent for the rest of your long, healthy miserable life.
But could there be a better way?
An enterprising scientist decided to try a little twist on the CR experiment. He divided the genetically-similar animals into two groups, fed one group all it wanted and measured the intake, then fed the other group all it wanted – except every other day instead of daily. When the intake of the group fed every other day was measured, it turned out that that group – the intermittently fasted group – ate just about double on the eat days, so that overall both groups consumed the same amount of food. Animals in the one group at X amount of food per day while the animals in the other group ate 2X amount of food every other day. So both groups ate the same number of calories but the commonality ended there.
The intermittently fasted group of animals despite consuming the same number of calories as the ad libitum fed group enjoyed all the health and longevity benefits of calorically restricted animals. In essence, they got their cake and ate it, too. They got all the benefits of CR plus some without the CR.
Intermittent fasting (IF) reduced oxidative stress, made the animals more resistant to acute stress in general, reduced blood pressure, reduced blood sugar, improved insulin sensitivity, reduced the incidence of cancer, diabetes, and heart disease, and improved cognitive ability. But IF did even more. Animals that were intermittently fasted greatly increased the amount of brain-derived neurotrophic factor (BDNF) relative to CR animals. CR animals don’t produce much more BDNF than do ad libitum fed animals.
BDNF, as its name implies, is a substance that increases the growth of new nerve cells in the brain, but it does much more than that. BDNF is neuroprotective against stress and toxic insults to the brain and is somehow–no one yet knows how, exactly–involved in the insulin sensitivity/glucose regulating mechanism. Infusing BDNF into animals increases their insulin sensitivity and makes them lose weight. Humans with greater levels of BDNF have lower levels of depression. BDNF given to depressed humans reduces their depression. And increased levels of BDNF improve cognitive ability. In short, you want as much BDNF as you can get, and with IF you – if you’re a lab animal at least – can get a lot.
As the animal study data poured in, a few researchers began tentatively studying human subjects. A few studies appeared in the literature, and all showed positive benefits to humans who intermittently fasted. In none of the studies did subjects go completely without food for a day – most had one meal per day or ate ad libitum one day and reduced consumption markedly the next.
Even some academic physicians (including Don Laub, my old mentor when I did a plastic surgery rotation at Stanford) put themselves on a modified version of an IF and wrote about it the the journal Medical Hypothesis. Since May 2003, these folks have been on a version of the IF in which they consume about 20-50 percent of their estimated daily energy requirements on the fast day and eat whatever they want on the non-fast days.
Since starting their regimen they have
observed health benefits starting in as little as two weeks, in insulin resistance, asthma, seasonal allergies, infectious diseases of viral, bacterial and fungal origin (viral URI, recurrent bacterial tonsillitis, chronic sinusitis, periodontal disease), autoimmune disorder (rheumatoid arthritis), osteoarthritis, symptoms due to CNS inflammatory lesions (Tourette’s, Meniere’s) cardiac arrhythmias (PVCs, atrial fibrillation), menopause related hot flashes.
It all sounded good. But before I try anything out of the ordinary, and certainly before I suggest it to any of my own patients or readers, I view the idea through the lens of natural selection. In other words, I ask myself if the regimen in question would have been congruent with our Paleolithic heritage. If so, I move forward. If not, I take a long, hard look at all the biochemistry, physiology and pharmacology involved before I make any sort of recommendation.
In viewing IF through the lens of natural selection I came to the conclusion that IF was probably the way Paleolithic man ate. We modern humans have become acculturated to the three square meals per day regimen. Animals in the wild, particularly carnivorous animals, don’t eat thrice per day; they eat when they make a kill. I would imagine that Paleolithic man did the same. If I had to make an intelligent guess, I would say that Paleolithic man probably ate once per day or maybe even twice every three days. In data gathered from humans still living in non-Westernized cultures in the last century, it appears that they would gorge after a kill and sleep and lay around doing not much of anything for the next day or so. When these folks got hungry, they went out and hunted and started the cycle again.
If you accept, as I do, that the Paleolithic diet is the optimal diet for modern man due to our evolved physiologies, then you should probably also buy into the idea that a meal timing schedule more like that of Paleolithic man would provide benefit as well.
With this in mind, I recruited my wife into the process and we went on an intermittent fast . It wasn’t all that difficult, but I can tell you that the non-eating days were long. And the eating days were spent eating and dreading the non-eating day soon to follow.
After a few weeks, it dawned on me that we weren’t really following the same IF that all the lab animals were. The lab animals got food for 24 hours then went without for 24 hours. We, on the other hand, got food for about 16 hours (the waking hours) then went without for about 32 hours (8 hours sleeping, 16 hours awake and the next 8 hours sleeping). We decided to modify our fasting strategy…
(Continued in Part II)
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Posted on March 2nd, 2008