Evidence has been accumulating since the 1930s that calorie restriction - reducing energy intake below energy expenditure - extends lifespan and delays the onset of age-related diseases. CALERIE(Comprehensive Assignment of Long-term Effects of Reducing Intake of Energy), a study sponsored by America's National Institutes of Health took 48 men and women aged between 25 and 50 and assigned them randomly to either a control group or a calorie-restriction regime. Those in the second group were required to cut their calorie intake for six months to 75% of that needed to maintain their weight. The study is a landmark in the history of the field, because its subjects were either normal weight or only slightly overweight. At a molecular level, CALERIE suggests that these advantages are real. They showed drops in body temperature and blood-insulin levels - both phenomena that have been seen in long-lived, calorie-restricted animals. They also suffered less oxidative damage to their DNA.
The search for a drug that will stave off old age is itself very old. Scientists are trying to find a drug that will mimic the effect of calorie restriction. There is a family of enzymes called sirtuins, which act both as sensors of nutrient availability and as regulators of metabolic rate. These might provide the necessary biochemical link between starving and living longer. Some plant-derived molecules are known to activate sirtuins in yeast. One of these molecules, resveratrol, has increased the maximum lifespan of a small fish by 60%. However, some of these molecules are already in clinical trials for safety.
(Excerpted from "Manorama Yearbook 2007)
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