Caloric restriction and aging as viewed from Biosphere 2.

The low-calorie nutrient-dense diet consumed for 2 yr by the eight persons sealed inside the closed ecological space known as Biosphere 2, near Tucson, AZ, constituted a unique "experiment of nature," amounting to the first well-monitored application of a nutritional regimen proven in animals to substantially inhibit and delay time of onset of most age-related diseases, induce physiological changes characteristic of a functionally "younger" age, and extend both average and maximum lifespans. Over the 2 yr the eight persons demonstrated a substantial weight loss, remarkable fall in blood cholesterol, blood pressure, fasting blood sugar, and low white blood cell counts--exactly as seen in rodents on such a regimen. Studies in progress involving levels of cortisol, insulin, and glycosylated hemoglobin support the rodent similarity. Further studies will seek to determine whether additional among the large battery of physiologic changes induced in animals by caloric restriction are also induced in humans on a similar nutrient-dense, calorie-limited diet. Such evidence will pertain to the question whether the increased disease resistance and aging retardation shown by calorie-restricted rodents might also be expected to occur in humans.