"The rapid rate at which an athlete burns calories is not associated with either an increase or decrease in life span. There is, in fact, a theory that animals have only a fixed number of calories to burn during their life, but it is pure speculation, intended to explain why calorie-restricted rodents live longer. There is no evidence that an enhanced turnover rate of calories hastens the aging process. Based on our current level of knowledge, we would expect athletes to have longer or at least healthier lives than they would if they were not athletic.
"Exercise, diet and genotype all interact in complicated ways. Despite all our attempts to take our destinies into our own hands, genes seem to play a significant role in determining life span, susceptibility to disease and probably the effects of caloric restriction.