The Claim: You Lose Most of Your Body Heat Through Your Head

As reported in the Sunday PARADE magazine, this old saw comes from experiments done in the 1950s in which soldiers were sent into subzero temps wearing survival suits—and no hats. Shockingly, they lost a lot of heat through their heads!

Dr. Daniel I. Sessler, an anesthesiologist and expert on hypothermia at the University of Louisville medical school, said the popular myth stemmed from military experiments conducted five decades ago. In those studies, researchers dressed subjects in Arctic survival suits and exposed them to frigid conditions. But the suits only covered the subjects from the neck down  so naturally most of their body heat escaped through their heads.

As hypothermia expert Daniel Sessler, M.D., explained to the New York Times, you’d get the same results if any body part were exposed. Our faces and necks are five times more sensitive to temperature, so those areas may feel particularly vulnerable.  That isn’t a fair comparison, Dr. Sessler said. If you did the same experiment with someone wearing a swimsuit, only about 10 percent of the heat loss would come from the head.

The body responds to cold temperatures in at least two ways. One is the constriction of blood vessels in the arms and legs, reducing blood flow to the extremities. This protects the brain and vital organs in the trunk but leaves the fingers and toes susceptible to frostbite, in effect sacrificing them. Another response to cold is shivering, which generates heat. The face, head and upper chest are up to five times as sensitive to changes in temperature as other areas, Dr. Sessler said. This creates the illusion that covering up those areas traps in more heat, but clothing another part of the body does just as much to reduce overall heat loss -you’d lose just as much heat or more if you put on a hat and left, say, your left leg bare.


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