A decade ago, researchers investigating the antiaging effects of caloric restriction in humans set an ambitious goal for their study participants: decrease daily calories by 25%. On average, the group of nonobese adults were only able to cut down by 12% over the 2-year investigation, despite receiving intensive dietary and behavioral counseling. Significant changes in the study’s primary end points—resting metabolic rate and core body temperature—didn’t materialize either. These 2 factors are believed to slow aging in animal models of caloric restriction. Does that mean the study failed? Not necessarily.