Can extreme diets, through which you severely restrict calorie intake, increase life span? The answer is no, according to research released Wednesday by the National Institute on Aging. Researchers looked at more than 120 rhesus monkeys, restricting the diets of roughly half of them. The study found that the monkeys with lower-calorie diets were less likely to suffer from heart disease, diabetes, cancer, and other diseases. But that didn’t mean they lived longer than the monkeys with regular diets.