Science of Aging  

Clive McCay Discovers that Calorie Restriction Extends Life-Span in Rats

Who:Clive M. McCay, Mary F. Crowell
When:November 01, 1934
Methods: Feeding one group of rats a lower calorie diet than another group, and observing that the under-fed group lived longer
Institution: Cornell University
Where: Ithaca, New York, U.S.A

In the early 1930s Clive McCay started an experiment that would ignite the science of aging. His idea was to retard the rate of growth in rats to see if they lived longer. A nutritionist by training, McCay used a calorie restricted diet to retard growth of the rats.

McCay held concerns about when to implement the calorie restricted diet. If the diet started too soon after weaning, the rats might die prematurely. To resolve this problem, McCay divided his pool of 106 rats into 3 groups:

  1. 34 fed normally
  2. 36 fed normally till time of weaning, then put on a calorie restricted diet
  3. 36 fed normally till two weeks after weaning, then put on a calorie restricted diet

    Over a period of 4 years he followed 3 groups of rats, and found the low calorie group outlived those in the control group and had a higher median lifespan. The second group which started on the diet sooner than the third group lived even longer, confirming the diet's importance to lifespan.

    McCay summarizes his findings in four broad points:

    1. That the life span of rats can be extended with a diet that is low in calories but adequate in nutrients (vitamins/minerals)
    2. That the potential life span of animals is unknown, and greater than previously believed
    3. The differences in growth rates between genders in species may account for differences in lifespan
    4. There is a profitable potential to create and market low calorie but highly nutritious foods which can extend lifespan

      McCay's suggestion to the food industry to create low calorie but nutrient rich foods went unheeded at the time. Such products now exist in the form of diet foods or vitamin waters, but the best source is still fruits, and vegetables.

      McCay's other points where well headed and paved the way for research into the cause, and possible cure, for aging in humans.


      1. McCay, C. M.; Crowell, Mary F. Prolonging the Life Span. The Scientific Monthly, 1934, Volume 39, Issue 5, pp. 405-414