May 08, 2006
Slight Calorie Restriction Might Deliver Longer Life

Even a small decrease in calorie consumption delivered lower signs of age-related oxidative stress in rats.

GAINESVILLE, Fla., - A lifelong habit of trimming just a few calories from the daily diet can do more than slim the waistline - a new study shows it may help lessen the effects of aging.

Scientists from the University of Florida's Institute on Aging have found that eating a little less food and exercising a little more over a lifespan can reduce or even reverse aging-related cell and organ damage in rats.

The discovery, described this month in the journal Antioxidants and Redox Signaling, builds on recent research in animals and humans that has shown a more drastic 20 percent to 40 percent cut in calories slows aging damage. The UF findings indicate even small reductions in calories could have big effects on health and shed light on the molecular process responsible for the phenomenon, which until now has been poorly understood.

"This finding suggests that even slight moderation in intake of calories and a moderate exercise program is beneficial to a key organ such as the liver, which shows significant signs of dysfunction in the aging process," said Christiaan Leeuwenburgh, Ph.D., an associate professor of aging and geriatric research at the UF College of Medicine and the paper's senior author.

UF scientists found that feeding rats just 8 percent fewer calories a day and moderately increasing the animals' activity extended their average lifespan and significantly overturned the negative effects of cellular aging on liver function and overall health.

An 8 percent reduction is the equivalent of a few hundred calories in an average human diet and moderate exercise is equivalent to taking a short walk.

But most people can't reduce their calorie consumption at all for a sustained length of time. So this is an interesting result and a reason to eat slightly less. But few will manage to pull that off.

The researchers also found that RNA is an earlier biomarker for aging than DNA.

To reveal the workings of the body's chemical climate when aging-related damage happens, UF researchers tracked levels of biomarkers - chemicals and molecules present in the liver - in groups of rats. The liver, a crucial organ for maintaining good health during aging, cleans the blood and helps regulate the body's immune system. The researchers also plan to assess the same biomarkers in a study of rats' hearts, muscle and brains.

The research team was surprised to find one of the biomarkers, RNA, which is important for coding DNA and for protein synthesis, is more quickly damaged by aging than the more frequently studied DNA. RNA damage, therefore, could be an excellent early signal to indicate the onset of aging, researchers say.

"Because it is more sensitive to oxidative stress, RNA can be useful as an early marker of oxidative damage and even aging," said Arnold Y. Seo, a doctoral student in UF's Institute on Aging.

Better aging biomarkers that detect changes at earlier stages allow more rapid testing of potential life extending therapies.

Another study on rats found important clues for how calorie restriction lengthens life expectancy. Mice lacking a growth hormone receptor and with lower resulting insulin live longer than normal mice.

"The implication ... for pharmaceutical development would be that the signaling pathways of growth hormone and insulin may be logical targets for development of anti-aging medicine," Dr. Andrezej Bartke from Southern Illinois University in Springfield told Reuters Health.


However, in sharp contrast to its effects in normal mice, calorie restriction failed to increase lifespan in mutant mice lacking growth hormone receptor. "The present findings show that growth hormone resistant mice fail to respond normally to calorie restriction, a very effective life-extending intervention," Bartke said.

I think the idea here is that the reduction in growth hormone receptor delivers the life extension benefit that calorie reduction would normally deliver. So when calories are reduced in these mice there is not an additional benefit from the calorie reduction.

Update: You can read the paper in the Proceedings of the National Academy Of Science by Bartke's group in abstract and the full paper in open access.

Share |      Randall Parker, 2006 May 08 10:35 PM  Aging Diet Studies

ziel said at May 9, 2006 11:50 AM:

Dramatic changes in diet are indeed improbable for most people, but that's what most dieticians and diet pundits seem to call for. This study should encourage more modest and realistic changes.

One approach I feel works it to use simple substitutions. If you use cream in your coffee, switch to milk, and if you use milk switch to black until you get used to it and no longer crave the other. If you have egg and bacon sandwiches switch to a buttered roll and if you have that then switch to cereal. Go from whole milk to 2% to 1% and maybe even to skim. If you eat cheese burgers try skipping the cheese. Try eating the burger without ketchup and use sliced tomato and pickle instead. Just don't have fries or potato chips - have cole slaw instead. Try mustard on sandwiches instead of mayo or at least use half as much mayo with mustard. Don't have bread and butter during dinner. If you crave it hold off until the end of the meal. If you're wont to have ice cream at night try instead a glass of chocolate milk with ovaltine or chocolate syrup and 1% milk. If you could eat fresh fruit instead that would of course be ideal.

A diet-nazi would have a fit over these suggestions but they would indeed lead to eliminating hundreds of calories from the diet of the average bad-eater and are far more realistic than expecting meat-and-potatoes eaters to switch to high-fiber carbohydrates and multiple servings of vegetables all day. That would be great if they did, but it ain't gonna happen.

PacRim Jim said at May 9, 2006 5:23 PM:

I skipped dessert and life already seems longer.

Matthew Cromer said at May 9, 2006 6:06 PM:

If it were conclusively demonstrated that a complete abstention from sex would add 5 years to your life, would you give it up?

Lou Pagnucco said at May 9, 2006 9:53 PM:

Does anyone know whether there exist any soluble decoy receptors or receptor blockers for human growth hormone?

Possibly, these could act as CR-mimetics by reducing circulating HGH or by blocking it.

Brock said at May 10, 2006 5:28 PM:

Art de Vany claims to get the same benefit low calorie diets offer simply by fasting for a day once a week. He thinks this 'makes sense' from a Darwinian point of view, since hunter-gatherers would have an irregular, "feast & famine" food supply and (of course) evolution would have adapted us to take advantage of that fact. He's also found evidence in medical papers he has read, but he doesn't cite the papers on his blog. Presumably they will be cited in the book he's writing on his theories of "Evolutionary Fitness & Aging". At 67 his biological age is rated at 32.

sr said at May 10, 2006 5:31 PM:

Intermittent fasting -- fasting every other day, for instance -- is pretty dramatic, but it can be done. It would be nice to have a marker by which to tune one's diet, though, so one could tell how stringent is stringent enough. I had not heard of the RNA vs DNA issue before. Most interesting.

CASpears said at May 11, 2006 12:45 PM:

I'd rather live a year less and eat well today...sorry...I'm not starving myself to squeeze out an extra year or so...I want to enjoy life while I'm living it.

richard said at May 14, 2006 5:44 PM:

i have been eating every other day since last december and am maintaining my weight at 155 lbs , i am 5'8. my weight was 177 lbs. just eating every other day stopped the weight gain but did not take off the weight . to take off the weight i had to skip days of my normal eating ( if i ate on sunday i would not eat again til thursday ). i only eat one meal on my eating day . i tried to eat both lunch and dinner but the weight started to come back . i have three beers on my eating day and eat as much as i want from 5 at nite til bed time . this works perfect and is so rewarding , i never even feel hungry anymore .

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