Here, Chemical & Engineering News looks at the practice of calorie restriction: "lthough Paul McGlothin and Meredith Averill are in their early 60s, the married couple from New York State says that they feel at least 20 years younger. This is no idle claim: Their blood pressures, resting heart rates, and body fat percentages rival those of Olympic athletes. ... So what's their antiaging secret? For the past 16 years, McGlothin and Averill have been eating a carefully controlled, calorie-restricted diet. ... Scientists have known for decades that caloric restriction - reducing calorie intake without malnutrition - slows aging and extends life span in model organisms ranging from yeast to mice. Exactly why and how it confers these benefits in animals, and whether similar effects could be attained in humans, have been a mystery. ... Caloric restriction is about more than just being thin and fit. Something about eating a diet that is low in calories but nutritionally complete causes a dramatic reprogramming of cellular metabolism that can't be replicated by exercise or by eating smaller amounts of high-calorie foods. In laboratory animals such as fruit flies, roundworms, and mice, caloric restriction switches biochemical pathways on or off, resulting in higher insulin sensitivity, decreased inflammation, enhanced cardiovascular functioning, reduced muscle wasting with age, and improved resistance to cellular stress. Not only is normal aging slowed, but calorie-restricted animals are also less likely to develop age-associated diseases such as diabetes and cancer."