To eat or not to eat? New study provides evidence that maintaining a chronic caloric deficit improves health and extends life

July 10, 2009 at 5:59 pm 2 comments

As this ScienceDaily article explained a few weeks ago, “Experiment after experiment confirms that a diet on the brink of starvation expands lifespan in mice and many other species.”

Could humans actually benefit from a permanent diet that left them chronicaly deficient of the number of calories to maintain a healthy weight? Many of these studies were conducted with animals (relatively) far-removed from the human species, genetically speaking, such as worms and rats  — though speculation on this topic goes back to 2001, when the LA Times wrote a headline supposing that “Low-calorie diet given to mice may be key to longevity in humans.” Many people who have converted to a restricted calorie diet testify to having better cardiovascular health, and have been reported to live longer, than their peers who consume a “regular” amount of calories, but there has yet to be any experimental studies with humans that validate these anecdotes.

Today, however, the journal Science published the results from a much-anticipated longitudinal and experimental study about the health effects of a restricted calorie diet in primates. The title of the article, which can be accessed here, explains the main takeaway: “Caloric restriction delays disease onset and mortality in Rhesus monkeys” (Colman et al.).

The BBC (“Proof Mounts on Restricted Diet“) and LA Times (“Permanent diet may equal longer life“) provide fantastic summaries of the research. From the BBC:

Seventy-six rhesus monkeys were involved in the trial, which began in 1989 and was expanded in 1994.

Half had their diets restricted, half were given free rein at feeding time.

The rate of cancers and cardiovascular disease in dieting animals was less than half of those permitted to eat freely.

While diabetes and problems with glucose regulation were common in monkeys who ate what they wanted, there were no cases in the calorie controlled group.

In addition, while most brains shrink with age, the restricted diet appeared to maintain the volume of the brain at least in some regions.

In particular, the areas associated with movement and memory seemed to be better preserved.

And from the LAT:

“It adds to the evidence piling up that caloric restriction, independent of thinness, is a healthy way to stay alive and healthy longer,” said Susan Roberts of the Human Nutrition Research Center on Aging at Tufts University, who wasn’t involved in the study. “Less diseases in old age has to be something most everyone wants.”

Is caloric restriction the solution?

“Mild caloric restriction is beneficial to everybody,” said Dr. Luigi Fontana, a medical professor at Washington University in St. Louis.

In his examinations of people who have been practicing caloric restriction for an average of 6 1/2 years, Fontana found their heart function was equivalent to those of people 16 years younger.

Though the regimen sounds grueling, it is hardly a starvation diet, experts said.

It typically begins with an in-depth assessment to determine how many calories an individual needs to consume to maintain a healthy weight. Then that number is shaved by 10% to 30%.

Fourteen deaths in the control group were attributable to age-related diseases, compared with five such deaths among the animals that ate 30% fewer calories, according to the study.

The rates of cardiovascular disease and pre-cancerous cell growths were twice as high in the control group compared with the reduced-calorie group.

The researchers also noted that although five of the control monkeys became diabetic and 11 were classified as pre-diabetic, all the calorie-restricted animals remained diabetes-free.

Brain scans revealed significantly less atrophy of gray matter in the monkeys that ate less.

They even looked less wrinkled and flabby.

In all, the monkeys on caloric restriction “appear to be biologically younger than the normally fed animals,” the researchers wrote in their report.

The researchers and authors, though, caution against using this study as justification for a dramatic change in human diet.  As the BBC article closes,

“Monkeys may be a close relation but there are significant differences which means not everything we see in them can be translated to humans,” said Catherine Collins, spokeswoman for the British Dietetic Association.

“And there should be some serious reservations about cutting calories so dramatically, particularly for anyone under the age of 30. Any such diet would need to be very balanced to avoid malnutrition, and it would be a long-term commitment.”

And would a restricted calorie diet mean having to give-up all of our favorite indulgences? Maybe not. Richard Weindruch, senior author of the study,  “has started a company to create drugs that would provide the same health benefits without the need for extreme dieting.”

Note: The NYT had a story on the Rhesus monkey and restricted calorie research a few years ago. It’s also worth a read and can be found here.

Also, New York magazine published a provocative cover story title “The diet to end all diets,” in which one of their writers documents his two-month experiment on an extreme restricted calorie diet. Read “The fast supper” here.

play, think…
J.R. Atwood


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2 Comments Add your own

  • 1. jleeger  |  July 10, 2009 at 6:19 pm

    I have a lot of questions after reading this post.

    I haven’t read the article you’re citing yet, but I wonder about the following:

    How much physical activity did the monkeys participate in?

    How much longer did diet-restricted monkeys live than their free-roaming counterparts? (I mean, was it years, days, or minutes?)

    Finally, what was the difference in mortality risk-factors and disease between the median of the group (or even the upper part of the median), and the “tipping point” for dietary mortality-risk?

    With reference to the last question, we know from studies in exercise science that the elite athlete actually has a very small difference in health benefit than the upper-middle level athlete. (Of course, athletics aren’t about ‘health,’ but that’s a different topic).

    My question would be, where does the “tipping point” occur? At what point do you exceed healthy parameters and tip into unhealthy ones as far as your energy balance goes? I think the energy balance is an important topic here, too. Captive animals have a significantly reduced level of activity compared with their wild counterparts.

    I’m not entirely convinced starvation is a good tactic for longevity, but I look forward to reading the paper! No animal can live that way in the wild. Survival requires occasional periods of feast and famine. However, these scientists appear to have done a good job of recreating our modern environment. Plenty of nutrients, no requirement for movement.

  • 2. J.R. Atwood  |  July 13, 2009 at 2:16 pm

    Hi Josh,

    You pose an important series of questions that initiate a conversation about physical activity and diet…

    I think this research about the so-called “starvation diet” is intriguing. But I would like to see an experiemental study conducted that looks to see whether the relationship between caloric restriction and various health indicators is a threshold or gradual phenomenon. For example, compared to a control group — which consumes a “normal/regular” diet — what are the health effects on Rhesus monkeys who trim their caloric intake by 10%, 20%, 25%, 30%, and 40%? I imagine, like you, that there would be a “tipping point” of energy balance — a narrow range after which there is a diminishing value of health outcomes for each percentage of caloric restriction.

    Also, I want to know what happens if Rhesus monkeys were subjected to regular vigorous aerobic activity and had to trim their caloric intake — what, then, would be the influence on health indicators like cardiovascular fitness, cancer rates, mortality, and cognitive functioning?

    I simply can’t imagine a severely restricted diet being beneficial to someone who engages in regular vigorous physical activity, though I am often surprised by what scientists and researchers discover.

    And if it is confirmed that a restricted diet does not promote better health outcomes among Rhesus monkeys (or humans) who engage in regular vigorous physical activity, I am curious to know the kinds of recommendations physicians may offer their patients, and the habits that we may develop as a result of such research: It seems that people would have a choice, if you will, between living on a permanent diet (significantly restricting their caloric intake by upwards of 30%), or doing 20-30 minutes of aerobic and load-bearing exercise every day. Each lifestyle may offer significant health benefits, but could be dangerous in combination. Which option (if any) would people prefer?

    Thanks for the thoughtful comment!


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Jason R. Atwood

I'm an avid trail runner and doctoral student at U.C. Berkeley who studies motivation and the relationship between the mind and body. This blog is a forum to share research, news, and musings about these topics of interest. More

Play is the beginning of knowledge.

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