Much research is ongoing that is looking at interventions that might slow aging and increase life spans. Scientists are studying the use of antioxidants, hormones, gene therapy and caloric restriction. To date, only caloric restriction, undernutrition without malnutrition, has been documented to extend life spans--and thus far, only in experimental animals¹³.

Caloric restriction has been shown to increase both average and maximal life span in laboratory rats and mice. In one study, the mice were divided into several groups. One group was fed ad libitum, as much as they wanted, while the others were given defined amounts, in progressively smaller increments. The group with the lowest caloric intake, about 35% less than the freely fed mice¹⁴, lived an average of 53 months, longer than any previously described laboratory mice. In another study in rats, it was demonstrated that restriction could be initiated in adult animals with almost the same longevity benefits as if started in young animals. These same experiments showed that the longer the duration of restriction the greater the extension of life¹⁵.

Other mouse and rat studies have demonstrated that not only is the life span increased, but that physical processes are maintained in a more youthful state, and age-related diseases are either delayed or prevented¹⁶.

Early primate studies suggest that caloric restriction can retard some of the decline in metabolic processes associated with aging, most notably the phenomenon of insulin resistance¹⁷. Insulin resistance refers to the decreasing ability of circulating insulin to drive glucose into cells where it can be utilized as fuel.

Human primates bear many similarities to our non-human cousins. Increased body weight increases our insulin resistance, as does aging¹⁸. While studies have shown glucose-rich diets to decrease longevity in mice¹⁹, no conclusive studies have documented the same thing in humans. Still, several prominent scientists have proposed that insulin resistance is also a contributor to human aging.^20,21

Much recent research has documented that visceral body fat is a far more dynamic human tissue than has been realized. Fat is not an inert annoyance; it is effectively an active gland, producing hormones that are active throughout the body²². These hormones include tumor necrosis factor-alpha, which has been shown to worsen insulin resistance²³. Another hormone produced in fat is leptin, which reduces the amount of stress hormones the body can release²⁴, and increases thyroid activity (which increases energy expenditure²⁵). Caloric restriction up-activates stress hormones and down-regulates thyroid hormones, possibly by limiting leptin's activities²⁶.