Findings from this 2-year Calorie Restriction CR trial in healthy, non-obese humans provide new evidence of persistent metabolic slowing accompanied by reduced oxidative stress, which supports the rate of living and oxidative damage theories of mammalian aging....according to the rate of living theory, those individuals who are the most efficient at utilizing energy should experience the greatest longevity....Notably, many biomarkers of aging...were also improved in these young, healthy individuals.