For years we’ve known that severe caloric restriction with adequate nutrition (CRAN) extended animals’ lifespans. Some people even practice CRAN, eating a third less than normal, in an effort to extend their own lives — what we call the “live longer by not really living” plan. According to Leanness, Not Diet, May Be Key to Long Life though, the key may not be near-starvation dieting; it may just be staying lean:
Many studies have shown that animals live longer when they eat, on average, about 30 percent less than normal. The findings have led scientists to speculate that people, too, can extend their lives by dieting.
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Dr. C. Ronald Kahn of the Joslin Diabetes Center at Harvard Medical School and colleagues genetically engineered a mouse that lacked a gene called fat-specific insulin receptor. This change limited the action of insulin on fat cells.The mice, which they nicknamed FIRKO mice (for fat-specific insulin receptor knock-outs), fed freely without gaining much fat and also lived longer than normal mice.
They had 50 to 70 percent less fat, no matter what they ate, and also were less likely to develop diabetes than normal mice. They lived on average 134 days, or 18 percent longer than normal mice. By the age of 30 months half the normal mice had died but 80 percent of the FIRKO mice were still alive.