Why all the recent hubbub about calorie restricted diets? It is because calorie restriction is a scientifically proven method for extending life. Scientists have known for seven decades that calorie restriction will significantly extend the life of everything from yeast to mammals. How does this work?
It seems no one is quite sure precisely how it works except to say it has to do with the activity of genes and inter-cellular structures. In 2007, researchers from Harvard Medical School discovered two genes that seem to be the gatekeepers for cellular longevity. Prior to this, Leonard P. Guarente, professor of biology at MIT had discovered (2000) that restricting calorie intake activates the gene SIR2. Precisely why this gene tends to remain inactive when calorie supply is abundantly adequate or why restricting calories activates it remains a bit of a mystery. However, when it is activated it apparently provides information that slows the aging process. Guarente demonstrated that SIR2 is crucially involved in extending the life span of yeast and in the roundworm. It seems that it all has to do with energy preservation in mitochondria (cell structures that, among other activities, convert food to energy). Cell death increases as mitochondria lose energy. The stress of calorie restriction triggers the production a molecule within the mitochondria that results in increased strength and energy for the mitochondria. Consequently, cell death is reduced.
Well, that is just great for yeast and roundworms but what does that have to do with you and I? It has to do with the fact that mammals, including humans, carry a very similar gene. If calorie restriction will extend the life of yeast and worms, why not mammals that have a similar gene.
Additional studies have shown that a similar restriction in calories can extend the life span of rats by as much as forty to fifty percent. If rats can extend their life by forty to fifty percent, why not humans? What if it turns out to be only a ten percent increase in humans? Would you balk at the opportunity to add seven or eight healthy years to your life? I think not. Have we at last found the fountain of youth?
As it turns out, the calorie restricted diet as touted may be the nutritional spam of the century -and we are not talking about the kind that comes in a can. Yes, rats are mammals. Yes, we have a very similar longevity regulating gene. And yes, rats on a calorie restricted diet did increase their life span by up to fifty percent. What the purveyors of this diet are not telling you is that the calorie restriction was so severe that the reproductive system of the rats shut down. If you think you have seen some tough diets, wait until you try that one.
We are not talking about cutting down on the cherry pie or dropping the after dinner dessert. This is about cutting your normal diet by thirty percent. Assuming normal to be the calories needed to maintain your body weight at the standard set by the Metropolitan charts, you can figure your normal calorie intake to be approximately ten times your ideal body weight. So if your ideal weight requires two thousand calories per day, your rat diet would be thirty percent or six hundred calories less than that or approximately fourteen hundred calories. I suppose that is doable although I cannot understand why anyone would want to live another ten years on such a diet. As, UCLA evolutionary biologist John Phelan reportedly said, “I once heard someone say caloric restriction may not make you live forever, but it sure would seem like it.”
Beside the general misery of trying to live on such a diet “as though to breathe were life”, the real problem comes when your ideal body weight is about one hundred sixty pounds or less. At this body weight your ‘normal’ calorie requirement is sixteen hundred calories or less per day. Reduce that by thirty percent and you are below twelve hundred calories per day and this is a limit we are told we should not exceed without careful medical supervision; i.e. it is unhealthy. The fountain of youth seems to be toxic. Now what are we to do?
The good news is that exercise, in concert with a healthy diet and the avoidance of ingesting toxic substances (e.g. nicotine) has an effect on cellular activity very similar to that of severe calorie restriction. Barbara C. Hansen, professor of physiology in the School of Medicine at the University of Maryland makes the observation that the lifestyle of an athlete would normally extend life span. Why? Because it involves behaviors such as regular exercise, a healthy diet that eliminates obesity and no substance abuse. Those are behaviors that reduce the risk of numerous life shortening diseases including cardiovascular disease - an almost completely preventable disease that claims the life of almost a million Americans every year. The bottom line, according to Ms. Hansen is this, an “athletic lifestyle won’t necessarily cause you to live to 100, but it might extend your life span from, say, 70 to 80.” That is about what you would expect from a severely restricted calorie regimen. And, we might add, it will be a much more healthy and enjoyable life given that studies have also shown that excessive leanness is about as unhealthy as excessive weight.