In this issue’s cover story, science writer Sharon Begley tackles a weighty topic: Why are extra pounds so easy to gain and so difficult to lose for good? She addresses the frustration many feel after attempting “sure-fire” methods of shedding weight only to fail time and time again. “You may see the unending quest for weight loss differently,” Begley writes,” as evidence that shedding pounds and keeping them off seems to be harder than growing a third arm.”