Mattson thinks that intermittent fasting acts in part as a form of mild stress that continually revs up cellular defenses against molecular damage. For instance, occasional fasting increases the levels of “chaperone proteins,” which prevent the incorrect assembly of other molecules in the cell. Additionally, fasting mice have higher levels of brain-derived neurotrophic factor (BDNF), a protein that prevents stressed neurons from dying. Low levels of BDNF have been linked to everything from depression to Alzheimer's, although it is still unclear whether these findings reflect cause and effect. Fasting also ramps up autophagy, a kind of garbage-disposal system in cells that gets rid of damaged molecules, including ones that have been previously tied to Alzheimer's, Parkinson's and other neurological diseases.
One of intermittent fasting's main effects seems to be increasing the body's responsiveness to insulin, the hormone that regulates blood sugar. Decreased sensitivity to insulin often accompanies obesity and has been linked to diabetes and heart failure; long-lived animals and people tend to have unusually low insulin, presumably because their cells are more sensitive to the hormone and therefore need less of it. A recent study at the Salk Institute for Biological Studies in La Jolla, Calif., showed that mice that feasted on fatty foods for eight hours a day and subsequently fasted for the rest of each day did not become obese or show dangerously high insulin levels.
The idea that periodic fasting may offer some of the same health benefits as continuous calorie restriction—and allows for some feasting while slimming down—has convinced an increasing number of people to try it, says Steve Mount, a University of Maryland genetics professor who has moderated a Yahoo discussion group on intermittent fasting for more than seven years. Intermittent fasting “isn't a panacea—it's always hard to lose weight,” adds Mount, who has fasted three days a week since 2004. “But the theory [that it activates the same signaling pathways in cells as calorie restriction] makes sense.”
On Thin Ground
Despite the growing enthusiasm for intermittent fasting, researchers have conducted few robust clinical trials, and its long-term effects in people remain uncertain. Still, a 1956 Spanish study sheds some light, says Louisiana-based physician James B. Johnson, who co-authored a 2006 analysis of the study's results. In the Spanish study, 60 elderly men and women fasted and feasted on alternate days for three years. The 60 participants spent 123 days in the infirmary, and six died. Meanwhile 60 nonfasting seniors racked up 219 infirmary days, and 13 died.
In 2007 Johnson, Mattson and their colleagues published a clinical study showing a rapid, significant alleviation of asthma symptoms and various signs of inflammation in nine overweight asthmatics who near-fasted every other day for two months.
Detracting from these promising results, however, the literature on intermittent fasting also includes several red flags. A 2011 Brazilian study in rats suggests that long-term intermittent fasting increases blood glucose and tissue levels of oxidizing compounds that could damage cells. Moreover, in a 2010 study co-authored by Mattson, periodically fasting rats mysteriously developed stiff heart tissue, which in turn impeded the organ's ability to pump blood.
And some weight-loss experts are skeptical about fasting, citing its hunger pangs and the possible dangers of compensatory gorging. Indeed, the most recent primate study on calorie restriction—the one that failed to extend life span—underscores the need for caution when radically altering the way people eat.
Still, from an evolutionary perspective, three meals a day is a strange modern invention. Volatility in our ancient ancestors' food supplies most likely brought on frequent fasting—not to mention malnutrition and starvation. Yet Mattson believes that such evolutionary pressures selected for genes that strengthened brain areas involved in learning and memory, which increased the odds of finding food and surviving. If he is right, intermittent fasting may be both a smart and smartening way to live.
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Add CommentThere's a big piece missing here, which is that intermittent fasting has fewer positive benefits and many more negative benefits for women. A lot more research on women specifically is needed, but it seems from what's out there that the hormonal response is quite different between the sexes. A good review of the existing studies and their implications for women can be found here:
Reply | Report Abuse | Link to thishttp://www.paleoforwomen.com/shattering-the-myth-of-fasting-for-women-a-review-of-female-specific-responses-to-fasting-in-the-literature/
I get so hungry when I fast, but yes, I may eat less, or more simple like a piece of bread.
Reply | Report Abuse | Link to thisGreat article, and this wisdom has been bolstered by circumstantial statistics for decades. What has not been tested under the scientific method is the underlying set of contributors, which result in this set of observation statistics, the correlation between lower caloric consumption and longer life, occurring. The hypothesis is not "My set of statistics observed = valid," rather the Hypothesis is "Factor Y results in a statistically significant covariant contribution in domain A and B simultaneously in one sub-species in the same environment and familial genome"
Reply | Report Abuse | Link to thisAs we now see that a very significant portion of the day's caloric burn is enacted by the brain and not the body, would we now consider that thinkers die earlier? I am not sure that the evidence would support this contention. As we find that some excessive caloric intakes are associated causally with specific illnesses, illnesses pandemic in the United States (for instance the gram negative toxic impact of h. pylori on the human blood sugar serum, or diabetes and heart disease links), we must weave into the continued falsification hierarchy the hypothesis that excessive caloric consumption is an outcome profile and not an input factor; a symptom of an underlying cause, which is peer to, and not prerequisite to a shortened lifespan. This science has yet to be done. But in the meantime, yes - I plan to lower my caloric intake accordingly. Great stuff! - TES
I think that periodic fasting would closely resemble the way humans have eaten for thousands of years. It make sense then for evolution to have 'selected' for genes that make this a 'healthy' way to live. I also think that period stressing of our systems is good for us. Like exercise is a method of stress that build fitness. Perhaps going hungry is a good stressor that strenghens other systems.
Reply | Report Abuse | Link to thisIn a more natural life sytle Fasting is Essential for physical ,mental and spiritual health . The "hormonal response" at present(normal)is in Horrible Disarray . Commercial Production of meat, dairy and poultry along with 'genetically modified' vegetables and grains has inundated ,most of what we eat ,with artificial hormones,antibiotics and multiple toxins from pesticides and petroleum based fertilizers.Add to that Further Processing, preserving, stabilizing, sweetening, coloring, flavor enhancing,...Well,that's the point .All of History in Every Culture has Fasting rituals or customs . In winter time the PLANET Fasts .A time to rest purely 'in tune' with nature! Remove the unnecessary debris from your Heart and Arteries , bloodstream,lungs,muscles,and intestines - herbal teas might be added.Fasting removes the Impurities in our Souls .Doing without,at the Time the Earth Offers the Least.Personal Sacrifice,Facing temptation ,Strengthening your own personal resolve and sharing with friends and family . Systematic under eating and periodic fasting are good for the person and the Planet.
Reply | Report Abuse | Link to thisFree Radic Biol Med. 2011 Oct 1;51(7):1454-60.
Reply | Report Abuse | Link to thisLong-term intermittent feeding, but not caloric restriction, leads to redox imbalance, insulin receptor nitration, and glucose intolerance.
Calorie restriction is a dietary intervention known to improve redox state, glucose tolerance, and animal life span. Other interventions have been adopted as study models for caloric restriction, including nonsupplemented food restriction and intermittent, every-other-day feedings. We compared the short- and long-term effects of these interventions to ad libitum protocols and found that, although all restricted diets decrease body weight, intermittent feeding did not decrease intra-abdominal adiposity. Short-term calorie restriction and intermittent feeding presented similar results relative to glucose tolerance. Surprisingly, long-term intermittent feeding promoted glucose intolerance, without a loss in insulin receptor phosphorylation. Intermittent feeding substantially increased insulin receptor nitration in both intra-abdominal adipose tissue and muscle, a modification associated with receptor inactivation. All restricted diets enhanced nitric oxide synthase levels in the insulin-responsive adipose tissue and skeletal muscle. However, whereas calorie restriction improved tissue redox state, food restriction and intermittent feedings did not. In fact, long-term intermittent feeding resulted in largely enhanced tissue release of oxidants. Overall, our results show that restricted diets are significantly different in their effects on glucose tolerance and redox state when adopted long-term. Furthermore, we show that intermittent feeding can lead to oxidative insulin receptor inactivation and glucose intolerance.
PMID: 21816219
Intermident fasting seems like a pretty bad idea in light of this study.
The only impartial study I've seen involving food intake and lifespan was the comparison of lifespans of Swedes born in famine or plenty years. Those born in years with abundant harvests died significantly younger than those born in famine years.
Reply | Report Abuse | Link to thisWe have known for centuries that the wealthy tend to have much worse diets and lifestyles. It is called "succeeding to death".