Quercus:
CR has been studied for a long time. I believe the first finding was almost a hundred years ago. But little human research has been done. There is only anecdotal evidence, but very positive. Anyone who goes on a CR diet has had an improved blood lipid profile, an improved glucose tolerance, and other positive factors. Unfortunately only the most extreme of people actually go on one of these diets.
Research has found an increase in lifespan in every species studied with this diet. They have yet to finish a study with monkeys, but it is looking very positive. I am of the belief that if it has worked for every other species tested, I don't see why it would not work for humans.
They have found that as little as 10% reduction in food produces a 10% increase in lifespan. And the correlation seems to keep up. For example a 20% reduction in food results in a 20% increase in lifespan, and 30% reduction equated to 30% increase. I believe it maxes out at 40%, so there is no benefit to greater then a 40% reduction in food consumed.
I should mention that CR is often called "undernutrition without malnutrition". All these diets were designed so there were no lack in vitamins and minerals. Often they would choose nutrient dense foods.
I have a theory about CR that I am putting together that might make it workable for most people, based on fairly recent research. I am putting an article together and will see if Testosterone magazine will accept it for publication.
I am convinced that I will live to 120 – 140 once I fully adopt my plan, and without sacrificing the ability to still gain muscle. And this is assumes current medical technology.