One way in which calorie restriction resists age-related issues with mitochondrial function in your cells is likely to be by encouraging autophagy, the process of recycling damaged cellular components - such as mitochondria, the power plants of your cells. Here, researchers note that one component of mitochondrial function, the malate-aspartate shuttle, declines with age, but is restored by calorie restriction: "Dietary restriction (DR) influences several physiological processes, retards the incidences and severity of various age-related diseases and extends lifespan of various animal species. The effect of DR on the activities of malate-aspartate shuttle enzymes [was] investigated in the liver and kidney of adult (5-months) and old (21-months) male mice. The results show that the activity [of the enzymes] is decreased significantly in the liver and kidney of old mice compared to adult ones. However, DR in old mice reverses significantly the enzyme activities to a level closer to adult animals. ... our results suggest that the late onset of DR in older mice reverses decline in malate-aspartate shuttle enzymes and that it may allow a better metabolic regulation in older animals." More evidence that it's never to late to start on calorie restriction - there are benefits to be had even if you are already aged.

Link: http://www.ncbi.nlm.nih.gov/pubmed/17932783