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Big Hint That Eating a Lot Less Won’t Let You Live Longer

The views expressed are those of the author and are not necessarily those of Scientific American.

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A skinny restricted-diet monkey is not expected to live longer than a portly companion

Aging researcher Thomas Kirkwood asked a roomful of scientists recently whether they thought that restricting calorie intake by 10 to 40 percent would extend lifespan, as it sometimes does in mice and roundworms. A majority of those present raised hands in assent. It has become a sort of conventional wisdom among scientists and the general public that calorie restriction extends lifespan. Even before hard scientific evidence was in, some people adopted the practice, foregoing rich desserts for the rest of their lives in the hope of arriving at a tenth or eleventh decade.

Kirkwood might get a very different response from the scientists he questioned if he asks the same question this afternoon or this evening. And it should be interesting to log onto the life-extension blogs and listservs in the wee hours.

A National Institute on Aging study published online today in Nature shows that more than 20 years of limiting calorie intake by 30 percent in a group of rhesus monkeys did not allow them to live longer than a control group of monkeys who were eating a normal, unrestricted diet. “I think the message is that a caloric restriction response, if it exists for monkeys and by implication humans, may occur only under the narrowest conditions,” says Steven N. Austad, a professor at University of Texas Health Science Center San Antonio, who wrote an accompanying commentary in Nature.

A similar monkey study of limiting dietary intake at the University of Wisconsin showed some benefit for extending lifespan, but Austad, in his Nature essay, raised the question of whether that might be related to their feeding regimen—the unrestricted Wisconsin monkeys were heavier and perhaps unhealthier and shorter-lived than the National Institute of Aging control group because they were able to eat  as much as they wanted.

Other questions arose about whether the removal from the Wisconsin study analysis of some monkeys who died from non-aging-related causes might have burnished the results. “Both studies are impressive bodies of work and I have the greatest respect for both teams,” says Kirkwood. “I do think the earlier results from the Wisconsin study revealed an eagerness to show the intervention worked—entirely understandable when so much time and resource has been invested into it. Taken together, the studies give significant reason to suppose that rodents are different from long-lived primates, but that should not come as a surprise.”

All of this is not necessarily a reason to rush out to buy McDonald’s stock. Older restricted-diet monkeys at the National Institute of Aging did have healthier measures of blood glucose and a blood lipid  than did their heftier companions. But it throws a chink into what many scientists—and a burgeoning dietary supplements industry (peddling resveratrol and other supplements said to mimic restriction)—thought was fast-becoming an established tenet of endocrinology and gerontology, that severely cutting calories would up the chances of living longer. Says Austad: “If we assume that rhesus monkey size in the wild approximates a healthy body weight [wild monkeys weigh less than all of those in both studies] then the Nature study suggests that reducing the diet of an overweight monkey such that it approaches  the weight of a wild monkey will improve some health metrics but not extend life.”

Austad adds: “Neither of these [studies] replicates what some people are experimenting on themselves with—which is normal weight people reducing their diets to the point of emaciation in the hopes that there will be a rodent-like boost in longevity.”

Mark Mattson, a neuroscientist at the National Institute on Aging who had practiced caloric restriction for 25 years, said he changed his diet in 2010 after he recognized that many of the caloric restriction studies in rodents had afforded the restricted animals a longevity premium because the control animals were the equivalent of “couch potatoes”— like the Wisconsin control group,  they were allowed to eat ad libitum, similar to humans digging into the potato chip bag when watching the game on TV.

Mattson continues research on fasting several days a week and eating normally the rest to determine whether it may help prevent the buildup of aberrant proteins observed among those with chronic diseases like Alzheimer’s or Parkinson’s, even if lifespan remains static. Mattson himself now follows an intermittent fasting diet.

The gainsaying about the National Institute of Aging study has already started. A whole cadre of researchers devote themselves to research related to caloric restriction and are likely to continue. “I think it’s unfortunate because it’s is such a long experiment that it will probably never be replicated,” says Matt Kaeberlein of the University of Washington, on the National Institute of Aging study.  “It’s really a single piece of data that can’t be interpreted and likely never will be able to be interpreted. Those of us who work in shorter-lived model organisms know very well that every once in awhile a lifespan experiment happens where CR doesn’t extend median or maximum survival. The difference is that we have repeated the experiment dozens of times.”

More primate research on caloric research continues, but some of the assumptions about a restricted diet have surely been shaken. One benefit of the new skepticism that will arise from this new study is a redirection of gerontology away from any temptation to view the field as a means to achieve Methuselah-like lifespans and a return to its main focus of optimizing health and avoidance of chronic disease up to the time of death.

The news you can use: exercise and maintain a healthy weight. Nothing profound here from the National Institute on Aging. Your mother probably beat the scientists to the punch.

Image source: National Institute on Aging












Gary Stix About the Author: Gary Stix, a senior editor, commissions, writes, and edits features, news articles and Web blogs for SCIENTIFIC AMERICAN. His area of coverage is neuroscience. He also has frequently been the issue or section editor for special issues or reports on topics ranging from nanotechnology to obesity. He has worked for more than 20 years at SCIENTIFIC AMERICAN, following three years as a science journalist at IEEE Spectrum, the flagship publication for the Institute of Electrical and Electronics Engineers. He has an undergraduate degree in journalism from New York University. With his wife, Miriam Lacob, he wrote a general primer on technology called Who Gives a Gigabyte? Follow on Twitter @@gstix1.

The views expressed are those of the author and are not necessarily those of Scientific American.

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  1. 1. Jojoscoble 5:02 pm 08/29/2012

    I love reading about health topics and different food regimes. It’s a difficult area of science to study as you are dealing with a lot variables, no-one is the same as anyone else so you really do need to do massive studies to get any trends to show.

    I love the research on the Alternate Day Fasting ADF so much so I’ve started doing it, just finished my 4th week and feeling good.(I’m writing a Blog look me up on Google – yeah, shameless plug).

    I think we can still learn a lot from studying more eating habits, perhaps more than we ever have been able. People do eat the same way for years on end with little variety, but finding these people and getting them involved on large studies is difficult. If everyone wrote a religious food diary like mine (On Googlecalendar) that might be a good start.

    My personal experiment is something that will shed personal light rather than scientific break-though.

    Link to this
  2. 2. bamw21 7:15 pm 08/29/2012

    I’m not sure how this conclusion can be drawn with only one study of monkeys living in a confined environment. That in itself has got to have an effect on their longevity or lack thereof. The picture show certainly suggests a form of confinement not conducive to normal animal behavior.
    They are being provided with food no doubt missing many of the food sources available to them if living in the wild.
    In addition it would be interesting to know how many monkeys were included in this study, how long they have lived in captivity, at what age they became part of the study, how many times they have been moved from one location to another just as starters.
    This study does not appear to have sufficient parameters with which to draw the final conclusion.

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  3. 3. Physics&Math 2:20 am 08/30/2012

    Wow. I don’t know where to start–I expect better from sciam.

    “One benefit of the new skepticism that will arise from this new study is a redirection of gerontology away from any temptation to view the field as a means to achieve Methuselah-like lifespans and a return to its main focus of optimizing health and avoidance of chronic disease up to the time of death.”

    How would that in any way be a benefit? Perhaps because if researchers stop trying to extend lifespan then this author can avoid the stress of allowing for the possibility of longer life? Please.

    And the last part of the statement? “return.. [to] avoidance of chronic disease up to the time of death.”
    What a profoundly unscientific statement. Do tell: what is going to cause this death, after the supposed abolition of chronic disease? Magic? Inevitability? Some tiny, ticking clock? Scientifically, there is every reason to view aging as the advanced stages of several diseases, some of which we may currently be unaware of, many of which seem to make each other worse. Indeed many gerontologists now view “aging” in precisely this way.

    This author, on the other hand, seems to yearn for a world where an inevitably fixed lifespan rids him of any pesky hopes, fears, or anxieties regarding the time of his impending death. Yet somehow he believes (hopes?) that a reasonable and possible direction of science would be simply to eliminate the chronic diseases that come with age, thereby rendering himself in top health, until the moment he suddenly expires.

    This possibility seems exceedingly unlikely, and profoundly unscientific, to say the list.

    Link to this
  4. 4. Physics&Math 2:27 am 08/30/2012

    Do these comments work?

    Link to this
  5. 5. Physics&Math 2:33 am 08/30/2012


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  6. 6. Physics&Math 2:43 am 08/30/2012

    So comments aren’t allowed here? Sciam should show that. Just lost the little diatribe I just wrote.

    Link to this
  7. 7. Physics&Math 2:56 am 08/30/2012

    “One benefit of the new skepticism that will arise from this new study is a redirection of gerontology away from any temptation to view the field as a means to achieve Methuselah-like lifespans and a return to its main focus of optimizing health and avoidance of chronic disease up to the time of death.”

    Wow. You are killing me.

    Link to this
  8. 8. ssm1959 5:15 pm 08/30/2012

    So much for the diet/lipid hypothesis of heart disease.

    Link to this
  9. 9. SachiNewDelhi 2:21 am 08/31/2012

    I prefer to enjoy my food. I don’t mind if that leads to a shorter lifespan for me.

    Oh and BTW, who gave the scientists the right to put those poor monkeys on a calorie-restricted diet?

    Were the monkeys trying to be supermodels?

    And Bingo! That gives an idea -> why not do the “studies” on calorie-restriction on aspiring or current and then retired supermodels who voluntarily starve as a job requirement?

    Link to this

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