A. Research dating back to the 1930s has shown that calorie restriction increases lifespan in animals. Results from preliminary human trials suggest that cutting daily intake of calories by 25 to 30 percent can help humans to live longer too. (That’s dropping down to 1,400-1,500 calories per day if you’re currently eating 2,000.) One explanation is that when you cut calories, you lower metabolic rate. This leads to fewer free radicals, which are formed during normal food metabolism but which damage DNA. And, in fact, one study of 48 overweight adults published in the Journal of the American Medical Association showed that after six months of calorie restriction (via diet or diet plus exercise), people registered lower levels of DNA damage. Still, some experts say that even if calorie restriction does work, the gains will be relatively modest. It’s likely to extend your lifespan but only by 3 to 5 percent, says UCLA evolutionary biologist John Phelan, who has conducted research on calorie restriction. “So after a decade of depriving yourself, you might get a couple of extra years.” We recommend meeting—just not exceeding—your calorie needs by eating a variety of nutrient-packed foods like fruits and vegetables, whole grains and lean proteins.