Caloric Restriction Nutrition

Does caloric restriction retard aging and extend life in humans? It is not yet possible to answer this often-asked question because a carefully designed and executed study has not been done with humans—nor is it likely that one will ever be done. In lieu of this, studies on the effects of caloric restriction on surrogates—nonhuman primates—were started in the 1980s and early 1990s.

The rhesus monkey is the primate species most studied. Since the maximum life span of this species is estimated to be forty years, information on the effect of caloric restriction on the length of life of the rhesus monkey will not be available until the year 2025 at the earliest. Thus far, however, many of the effects of caloric restriction found in rats and mice have also been observed in the rhesus monkey. For example, as in rodent species, caloric restriction in the rhesus monkey decreases body temperature, decreases blood glucose and insulin levels, and increases insulin sensitivity. This kind of information indicates that caloric restriction may have an antiaging action in the rhesus monkey similar to that in rats and mice. However, one must be cautious about jumping to any conclusions since the relationship between a particular physiological effect of caloric restriction and its antiaging action still remains to be established in rodents.

In rhesus monkeys, caloric restriction decreases the risk factors for age-associated cardiovascular diseases. It decreases both body fat and its age-associated increased distribution to the abdominal region, as well as decreasing the blood level LDL ("bad") cholesterol and increasing that HDL ("good") cholesterol. It also improves glucose tolerance and prevents the development of Type II diabetes. Nevertheless, a definitive answer regarding the antiaging action of caloric restriction in the rhesus monkey awaits the findings of the longevity studies.