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Calorie Restriction Doesn’t Extend Life, NIA Study Suggests

Monkeys Get Health Benefits, But No More Years

A new study casts doubt on 80 years of research suggesting that restricting calories without shorting nutrition may extend lifespan. Co-author Rafael de Cabo, an experimental gerontologist at the U. S. National Institute on Aging, and his colleagues found that calorie restriction conferred some health benefits on monkeys, but did not extend their life span. “One thing that’s becoming clear is that calorie restriction is not the Holy Grail for extending the life span of everything that walks on earth,” said de Cabo.

In 1934, researchers at Cornell University observed that laboratory rats fed a severely reduced calorie diet containing all of the required nutrients lived up to twice as long as rats fed normally. Calorie restriction (CR) is one of the few methods shown to increase lifespan in a variety of species, including yeast, flies, worms, fish, rodents, and dogs. There has never been—and may never be—a credible long-term clinical trial in humans; so we don't know whether CR prolongs human life. One of the longest running scientific studies in rhesus monkeys (genetically closer to humans than rodents) was begun at the University of Wisconsin in 1989. That study is ongoing and reports from time to time. In 2009, the Wisconsin researchers reported finding a trend toward longer life, but nothing determinative.

Roy Walford, MD, and his student Richard Weindruch are two of the researchers most commonly associated with calorie restriction as a means of extending life span. Carol and I first became aware of Dr. Walford and his work on aging in 1983, from the PBS TV program Nova. We followed up by reading his book Maximum Life Span. We were delighted to receive an order from Dr. Walford for our book Ripped about the same time. We returned his check and send him Ripped and Ripped 2. The second Ripped book cited Walford’s work in a section discussing whether extreme leanness is healthy.

We exchanged letters with Dr. Walford over the next several years. He was a professor in the Department of Pathology at the UCLA School of Medicine. I asked him to comment on the diet and exercise methods set forth in Ripped and Ripped 2. He responded by comparing my body and the bodies of volunteers subjected to six months of a 1500 calorie diet in a famous Ancel Keys experiment. “What a difference,” he wrote. His point, I believe, was that more calories combined with exercise are likely to lead to a more muscular and perhaps healthier body.  

In 1987, he sent us a notice announcing the publication of his book The 120 Year Diet. I read the book and wrote back saying that while the nutrition-packed whole foods in my diet are essentially the same as those recommended in his book, it appeared that I exercise more and eat more than he recommended. “This works, because it allows me to feel less restricted,” I explained.

Walford returned by telling me that he lives one block from World Gym in Venice; he said he worked out there on Saturday and Sunday. On three other days of the week, he said, he rode a stationary bicycle at home or swam at the UCLA pool. “So I am in favor of exercise…, but my exercise program is much less than yours,” he wrote.

There may not have been as much difference as it appeared. He trained five times a week and I trained three or four days a week; I also walked between workouts. My guess is that I was eating substantially more than he did and expending about the same number of calories in exercise. In our correspondence, he stressed that he was against “doing a lot of hypermetabolic calorie-burn-off exercise.” He favored calorie restriction over more exercise to achieve leanness. Walford believed in exercise to achieve specific goals. For example, he wrote that cardiovascular fitness, the major health goal, can be achieved in the equivalent of 15 miles of jogging per week. He didn’t believe in doing more.

I agree with that; but I would do less but harder. I believe in short, hard, focused exercise—and rest to allow recovery and growth. (I wrote a column in Muscle & Fitness detailing my exchanges with Dr. Walford; you’ll find it in my book The Lean Advantage 2.)

That brings us to the NIA study reported online August 29, 2012, in the journal Nature.

In the experiment, two sets of monkeys, one group aged 1 to 14 and another 16 to 23, were fed 30% less than what they would normally eat. Their outcomes were compared with two control groups of monkeys fed a normal diet. The calorie restricted monkeys, in both age groups, lived no longer than their normally fed counterparts. “However, a potential effect on maximum lifespan [opposed to average lifespan] cannot be ruled out,” Rafael de Cabo and his colleagues wrote.

Health benefits were mixed. Male monkeys on the restricted diet had significantly lower cholesterol levels, but the females did not see the same benefit. Cutting back calories appeared to lower cancer rates, but it also triggered a slight increase in cardiovascular disease. Another promising outcome was that various aging-related diseases appeared slightly later in the calorie restricted animals.

The NIA study began in 1987, two years before the Wisconsin study. That’s important, because the average lifespan of rhesus monkeys is 30 years; maximum lifespan is about 40. Scientists have to wait a long time to measure a difference in life span. Two more years of study could be telling.

There were other important differences in the NIA study and the Wisconsin study.

The 2009 status report on the Wisconsin study showed that calorie restriction extended the lives of the monkeys—with an important proviso. Deaths from non-age related causes were excluded—eliminating about half of the monkeys studied. If those deaths were included, the life extension disappeared. Many, but not all, scientists believe this compromised their finding on longevity. (The NIA study also excluded deaths from acute conditions that do not have an age-related increase in risk, such as intestinal bloat or injury.)   

Other differences between the two studies were less significant, but could still affect the outcome.

The Wisconsin control monkeys were allowed to eat as much as they wanted, while the NIA controls were given a set amount of food. The Wisconsin controls were fatter than those in the NIA study. The NIA researchers wrote that the slight calorie restriction on their controls may have actually given them a life extension advantage. In addition, their controls were fed a healthier diet than the Wisconsin control. For example, the NIA controls ate whole foods, while the Wisconsin controls were fed a purified diet. The NIA controls were also given vitamin and mineral supplements, while only the calorie restricted animals in the Wisconsin study received supplements.

Another difference was the origin of the monkeys in the two studies. The animals in the Wisconsin study came from India, while those in the NIA study came from India and China, which gave them greater genetic diversity.

Whatever the reason for the conflicting results, we are still a long way from knowing whether CR extends life in humans.

More than a few scientists are still optimistic that CR will live up to its early life-extension promise. Roy Walford’s protégé, Richard Weindruch, now 62 and a director of the Wisconsin study, remains hopeful. Even so, he admits that he is not very good at restricting his own calories. He says he might start trying harder. There is still hope at his age, he adds.

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The Wall Street Journal coverage of the NIA study elicited over 100 comments. The first response captured the sentiment of many. “Another food myth debunked. When you eat less, you don’t live longer, it just feels like it.”

While I wouldn’t characterize CR as a “myth,” I do agree that hunger is a steep price to pay for a few more years of life. Just thinking of cutting back 30 percent on my calorie intake makes me uncomfortable. Hunger and deprivation sink more diet plans than any other cause. Dr. Weindruch would seem to be an example. It’s not a matter of willpower and self control, it’s human nature. We are wired to eat when we are hungry.

Some people, I know, believe that I starve myself to stay lean. They’ve got it backwards. Avoiding hunger and feelings of deprivation is the secret to my long term success at body fat control. Telling yourself that you can’t have food only makes you want it more. I never do it. And I never tell anyone else to do it.

 I never starve myself—even before a photo shoot.

I eat wholesome foods that fill me up without giving me too many calories. I rarely crave more food. When I do, I have more and get rid of the craving.

That approach along with regular exercise keeps me lean and happy. I believe it’s also likely to help me live longer.

Whether or not calorie restriction works—and it may—it’s not for me.

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