The latest I have heard is that CR diets essentially slow most/all metabolic processes, limiting cell divisions. Limit that and you limit aging and attrition to some extent.

Health and aging is such a multi-faceted issue. My personal approach now is to try and balance things and do what I can to keep from harming my body (as opposed to going CR or some other means of forcibly extending life).

It seems to me that past a basic level of physical activity, doing less over time could extend life simply by limiting oxidative and other physical stressors on the body. This type of thinking goes hand in hand with a certain level of CR imo. Environmental stressors, mental stress, along with many things not taken into account also play a big role.

Also, I think a pretty strong argument can be made to stay near your bodyfat setpoint longterm as a means of keeping good health. Someone on a severe CR type diet can definitely have problems keeping a strong immune system for example. I also think it is pretty clear that being overfat isn't going to be the best bet for most people either.

There are obviously things to work around such as genetic predispositions and limitations, individual differences (what works for one person, blah, blah), and other risk factors like accidents that are not so easy to predict and control.

Also, a large argument against CR in the bodybuilding community and elsewhere centers on maintaining a higher quality of life rather than pure quantity. A higher quality of life might lead to greater happiness for some/many and this can work synergistically with other factors to help make a more complete picture of heatlh imo.