Keys’s data showed that the bodies of the men he starved saved calories in a manner similar to the way most people economize when they confront a severely reduced income: they prioritized “essential” organs like the brain but abandoned “expendable” costs like reproduction and drastically cut back on “reducible” functions like staying warm, active, and strong. By shrinking their muscles by 40 percent, they saved about 150 calories a day, leaving the starving men feeble and easily fatigued. Their hearts also got smaller by an estimated 17 percent, and their livers and kidneys shrank similarly.16
