In the early 1930s Clive McCay tested an idea to retard the rate of growth in rats and 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:
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:
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.