Controlling caloric consumption: protocols for rodents and rhesus monkeys.

One approach for investigating biological aging is to compare control-fed animals with others restricted in calorie intake by 20% or more. Caloric restriction (CR) is the only intervention shown to extend the maximum lifespan of several invertebrates and vertebrates including spiders, fish, rats and mice. The capacity of CR to retard aging in nonhuman primates is now being explored. The rodent studies show that CR opposes the development of many age-associated pathophysiological changes, including changes to the brain and changes in learning and behavior. One goal of studying CR in rodent is to determine the mechanisms by which it retards aging to design interventions that duplicate those effects. The methods that we use for conducting CR studies on mice and rhesus monkeys are described. We employ procedures designed to achieve a high degree of caloric control for all animals in the study. As used in our studies, this control includes the following features: 1) animals are individually housed, and 2) all individuals in the control group eat the same number of calories (i.e., they are not fed ad lib). Although this method results in strict caloric control for all animals, there seems to be considerable procedural flexibility for the successful conduct of CR studies.