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United States Department of Agriculture

Agricultural Research Service

Eating Less -The New Fountain of Youth
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W. Thomas Johnson

Sometime in the past, most of us learned about Juan Ponce de Leon, the 15th century Spanish explorer who spent a lot of time searching for the Fountain of Youth in what is now Florida and the Bahamas. Of course, Juan never found The Fountain of Youth because such a thing does not exist. Or does it? Although health and youth will never be restored by drinking water from some mythical fountain, scientists have shown there is a dietary intervention that has potential for increasing one's life span. That intervention is caloric restriction. Caloric restriction delays or even prevents some-age-related illnesses in laboratory rats and mice and causes a 30-50% increase in their maximum life spans. Also, preliminary results from an ongoing study have shown that mortality is decreased by about 50% in rhesus monkeys whose caloric intake has been restricted by 30% for 3 to 5 years. 

In addition to reducing mortality, restricting calories by 30% in monkeys decreases their body temperature, reduces the amount of insulin in blood, and increases the amount of a steroid hormone called DHEAS in blood that may be important for maintaining health. Another important finding with monkeys is that caloric restriction greatly reduces the severity of muscle damage caused by aging. The question is - do the findings with monkeys have any relationship to possible health benefits for humans? In a study investigating aging in healthy men, it was found that those with the lowest body temperatures, lowest insulin levels, and highest DHEAS levels had the longest lives. Thus, some of the changes caused by caloric restriction in monkeys correspond to what is found naturally in long-lived humans. This strongly suggests that reducing calories can extend human life. Furthermore, the finding that caloric restriction can reduce muscle damage in monkeys caused by aging suggests that the improvement in life span afforded by reducing calories may also be accompanied by a decrease in some of the afflictions, such as loss of muscle, that result from aging.

Although cutting calories in the diet holds promise for a longer, better life, more questions need to be answered before actual recommendations can be made for what level of caloric intake is most beneficial. Should caloric restriction start when one is young or is it okay to start in middle age? How many calories are best to cut back, is 10% reduction as good as 30%? How exactly does caloric restriction work to improve life span? Even as these questions are answered by more research, the one question that scientists cannot answer is; who, except maybe those wanting to lose weight, would want to reduce the amount they eat? After all, eating is pleasurable for most people. But in practical terms, reducing calories to a level that may improve life span may not be very difficult. A 150 pound person having normal body composition and weight and an average activity level needs about 16 calories per pound of body weight or about 2400 calories per day. If restricting caloric intake by 20% proves to be beneficial for life extension, then the new requirement for our 150 pound person would be 1920 calories per day. Cutting these 480 calories from one's diet may not be too painful. For example, a cheeseburger loaded with sauce, a large order of french fries and a large non-diet soft drink provides about 1750 calories, but a cheeseburger with ketchup, a medium order of fries, and a large diet soft drink provides 730 calories. This is a reduction of 1010 calories in a single meal that should be about as satisfying as the meal with more calories. So, the next time you are tempted to supersize your lunch order remember that you can make choices that may allow you to live longer and healthier. Reducing calories is not the Fountain of Youth, but it may help you age at a slower rate. Even Ponce de Leone probably would have been satisfied with that.

Last Modified: 10/23/2006
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