McCay used ‘mature’ rats that were given the opportunity to grow and develop. He then restricted calories without restricting nutrients. This resulted in a significant prolongation of life. Since, this finding was replicated by many. Nowadays the fact that caloric restriction prolongs life does not need extra proof. Researchers are merely trying to to explain this phenomenon. As usual there is a focus on the physiology to try and develop drugs that will prolong life. I think we should just take this caloric intake life extension relationship as a fact and focus our effort on finding ways of applying it. McCay did that by designing McCay’s loaf, a nutrient dense loaf.
I will leave with the link to the article. Yet, I would like to give you my own perspective: