"The point is, nutrient density, not calories, in food, is key. "
A lifestyle that helps avoid chronic health problems isn’t the only thing that determines how long you live, of course. Genes, too, help decide whether one’s life span ends up being average (which is about 78 in the United States) or extraordinary (like that of Frenchwoman Jeanne Calment, the oldest person on record, who died in 1997 at age 122). If I manage to live into my nineties, the genes I inherited from my gristle-eating great-grandmother will be partly to thank for it. Thomas Perls, M.D., who directs the New England Centenarian Study, believes that good health habits may be enough to carry many of us into our mid-eighties. To live longer than that, though, we need lucky genes.
But is that the whole story? What about that most elusive fountain of youth—a way to actually slow the aging process and extend the limits of longevity? A growing number of experts think they’ve found it. For years, in fact, researchers have been aware of a sure-fire way to put the brakes on aging.
In 1935, a team of Cornell University nutritionists discovered that mice fed one-third fewer calories than normal lived about 40 percent longer than mice that ate as much as they wanted. Since then, scientists have tested a Noah’s ark of creatures—from yeast cells and fruit flies to monkeys. In most studies, calorie restriction appears to increase life expectancy and protect against a host of diseases. Well into old age, animals typically remain more active and younger-looking, as well.
Scientists don’t know exactly why cutting calories may lengthen life, but the leading theory goes like this: When calorie intake falls short, cells sound an alarm, switching their priorities from reproduction to repair and maintenance, fending off genetic damage and the wear and tear caused by the effects of unstable oxygen molecules. Controlling this switch, researchers have learned over the past few years, are a class of enzymes called sirtuins, which affect how energy is delivered to cells. In a 2006 experiment straight out of science fiction, University of California, San Francisco, biochemistry researcher Cynthia Kenyon, Ph.D., tinkered with the equivalent gene in roundworms. The result: a mutant species with a life span six times longer than normal.