By Brian Manning Delaney

Calorie restriction is the only well-researched, effective means of retarding aging that is available to post-embryonic animals.

Calorie restriction, as it is used by life-extensionists, means a reduction in caloric-intake for the purposes of lowering one's rate of aging as well as preventing disease or the morbidity/mortality associated with disease.

For these ends to be achieved, a restriction of energy-intake must not also be accompanied by restrictions of most other essential nutrients, especially vitamins and minerals, at least insofar as such restrictions in essential nutrients would result in sub-optimal intakes of these nutrients.

This is important: calorie restrictionis not the same as "going on a diet," or simply eating less, or starving oneself.

One often sees other terms in the research literature, terms that connote a slightly different sort of diet, such as "food restriction," "dietary restriction," and so on. These different terms reflect, partly, different conceptions of the mechanism by which "calorie restriction" slows aging and prevents disease.

In some cases, the terms also reflect different dietary regimens used in experiments. Part of this terminological and methodological confusion results from the difficulty in isolating the effects of a low- calorie diet from the effects of other aspects of the experimental diets.

Some of the research that claims to be testing the effects of a calorically reduced, but not otherwise reduced diet has not, in fact, taken sufficient note of the reduction in protein that exists in the diets of the experimental animals, but considers protein only insofar as it contributes energy (calories) to the diet of the animals. Indeed, there are a few researchers who would call other researchers' "calorie restriction" experiments "PR" experiments.

The situation is even more complicated than this, given that minimal essential requirements for protein (for humans or rodents), as well as for other nutrients, have yet to be determined precisely.

Nevertheless, there is now widespread agreement that the reduction in energy-intake per se is responsible for most of the positive effects seen in these experiments, even if a few researchers think that the reduction in protein that usually exists in these experiments plays some role also.

The best terms to describe this sort of diet should perhaps be more general, like the "anti-aging diet," or "high/low diet" (high in "good" nutrients, low in "bad" ones), or "undernutrition without malnutrition" -- terms that Roy Walford often uses in his writings (see FAQ link below for bibliographical info on some of his work).

These terms capture the essence of the dietary anti-aging strategy, without presuming to have solved the technical questions about the absolutely optimal nature of an anti- aging diet, or the precise mechanisms by which the researched diets exert their effects.

Nonetheless, "calorie restriction," is in widespread use and captures the essence of the diet well enough that I will continue to use it, most of the time. I also sometimes call the practice of eating less for the purpose of living longer 'anorexia longaeva,' a term not without problems of its own.

Calorie Restriction By The Fasting Method

Instead of eating less on daily basis, periodic fasting can probably produce the same retardation in rate of aging as the much more commonly studied kind of calorie restriction. Studies have shown that rodents fed all they can eat, but fasted every two, three or four days, also have an increase in longevity, though the increase isn't quite as great as that of rodents on the standard kind of calorie restriction.

For some people, this might be an easier way of doing calorie restriction:

• Hunger is limited to two or three days a week, which might be easier psychologically, and
• The attendant weight-loss wouldn't be as great (the extreme, but periodic, restriction of the fasts seems to have a longevity-enhancing effect without a continual average reduction in caloric-intake).

This would probably need to be instituted slowly, like the standard way of doing calorie restriction. You could just eat your first meal of the day -- on days when you want to fast -- later and later, until you're not eating at all on your fasting days.

This method of calorie restriction, however, has not been researched nearly as intensively as the other method. It is possible that there are unknown dangers to periodic fasting.

Mild, Or "More Humanly Achievable" Calorie Restriction

Things become much, much less complicated when one decides to do a milder form of calorie restriction. A radical extension of life span will not be achieved by mild calorie restriction, but there is every reason to believe that significant health benefits would result.

Simply eating a very low-fat diet could actually amount to mild calorie restriction. Indeed, as indicated above, the purported benefits of very low-fat diets may result partly, if not primarily, from the almost inevitable reduction in energy intake entailed by this way of eating. Another easy way to practice mild calorie restriction would be to get into the habit of not eating to complete satiety.

Another way to practice mild calorie restrictionis simply to skip lunch. This is probably the easiest way to practice mild calorie restriction. An additional potential benefit of skipping lunch is the prevention of late afternoon fatigue. A recent study suggested that this benefit could be quite striking.

InfiniteFaculty.org

Initially posted at ChetDay.com