calorie consumption from the normal diet
with a balanced amount of protein, fat, vita-
mins, and minerals. In the 1930s, investigators
found that laboratory rats and mice lived
up to 40 percent longer when fed a calorie-
restricted diet, compared to mice fed a normal
diet. Since that time, scientists observed that
calorie restriction increased the lifespan of
many other animal models, including yeast,
worms, flies, some (but not all) strains of
mice, and maybe even nonhuman primates.
In addition, when started at an early age or as
a young adult, calorie restriction was found
to increase the health span of many animal
models by delaying onset of age-related dis-
ease and delaying normal age-related decline.
Two studies of calorie restriction in non-
human primates (the animals most closely