Any variations in biochemical activity between an animal species and ourselves would be taken into account when the results of research were evaluated.

Many of the experiments described produce an increase in average (or mean) life span of whole groups of animals (about 75 years in humans) as well as individual extension of maximum life spans (around 120 years in humans) along with a host of health benefits. Since these benefits are accompanied by a host of objective signs in systems (cell energy production function, for example) which are the same in humans and animals, and all involving biochemical pathways which are similar, or identical, it seems that we can indeed take seriously the evidence which these studies have produced.

This then is some of the evidence of what happens to animals and humans when dietary restriction is applied, voluntarily or experimentally, and why we can apply much of this knowledge to our own use. But, what is actually happening to the ageing process itself as these changes occur? How does dietary restriction work?