Why do we have to get old and die? There are 2 main theories. One is, we just wear out from use like a car or The Wonderful “One-Hoss Shay” (poem by Oliver Wendell Holmes, published in his “Breakfast-Table” column in The Atlantic Monthly September 1858). The other theory is we are genetically programmed to age and die. If we are programmed to die maybe we could change the program.
Numerous studies have shown that calorie restriction – eating less but not too little – can extend life expectancy by a big number. This has been demonstrated in worms and all kinds of bigger animals but not yet definitively in humans. We don’t understand how this works but the theory is that calorie restriction decreases metabolic rate and slows aging by decreasing wear and tear on the organism along the lines of theory one.
We will probably never be able to study in a randomized clinical trial whether calorie restriction can extend the life span of humans like we can with experimental animals but we can watch obese people who diet forever or people who try calorie restriction on their own and see what happens. Calorie restriction and weight loss does a lot of good things in these observational situations. We can also study calorie restriction short term. The CALERIE (Comprehensive Assessment of Long term Effects of Reducing Intake of Energy) trial was a study designed to determine the biological effects of two years of caloric restriction in humans. They reported on this a decade ago. (1) In this study they tried to get half of 218 non obese middle aged adults to decrease calorie intake by 25% but they only managed to accomplish a little less than half that for the study period. They lost 10% of their pre-study weight and some cardiovascular risk factors and thyroid hormone levels decreased and total daily energy expenditure decreased. But they didn’t change resting energy expenditure or body temperature like we see in the experimental animals. The modest decrease in calorie intake didn’t decrease their quality of life but the aimed for 25% decrease probably would have made them too tired and hungry – that’s probably why they did’t do it.
In the experimental animals they used 20 to 50% reduction and that dramatically extended life span and health span – staying healthy to the end. But that’s going to be impossible to expect non-crazy humans to do. But what about trying periodic short term fasting for 1 or 2 days? Turns out that could be almost as good. (2) It might also be less painful. While you are fasting all you organs shrink. When you start eating ageing they come back rejuvenated. Don’t do this if you are on insulin or diabetes drugs though.
John DiTraglia M.D. is a Pediatrician in Portsmouth. He can be reached by e-mail- email@example.com or phone-354-6605.