Last nails from EurekAlert!: "One early theory, the rate of living theory, held that every organism has a set amount of energy to expend. Once the animal expended that number of calories, the grim reaper was on the doorstep. Over the years, the theory has become much more sophisticated, but metabolic rate and aging have remained linked ... Runner mice that had access to a wheel expended 25% more energy over the course of their lives compared to both the runner group that did not have a wheel and the regular mice ... The rate of living theory would have predicted that the running group that expended more energy would die earlier than the two groups that did not ... This was not the case. There was no difference in life span between the two runner groups, even though one expended more energy." Recall that exercise is demonstrably good for health and resistance to age-related disease.