Hatless and pantsless in Seattle

When it comes to wrapping up on a cold winter's day, a cozy hat is obligatory. After all, most of our body heat is lost through our heads – or so we are led to believe.

Closer inspection of heat loss in the hatless, however, reveals the claim to be nonsense, say scientists. They traced the origins of the hat-wearing advice back to a US army survival manual from 1970 which strongly recommended covering the head when it is cold, since "40 to 45 percent of body heat" is lost from the head.

Rachel Vreeman and Aaron Carroll, at the center for health policy at Indiana University in Indianapolis, rubbish the claim in the British Medical Journal. If this were true, they say, humans would be just as cold if they went without a hat as if they went without trousers. "Patently, this is just not the case," they write.

The myth is thought to have arisen through a flawed interpretation of a vaguely scientific experiment by the US military in the 1950s. In those studies, volunteers were dressed in Arctic survival suits and exposed to bitterly cold conditions. Because it was the only part of their bodies left uncovered, most of their heat was lost through their heads.

The face, head and chest are more sensitive to changes in temperature than the rest of the body, making it feel as if covering them up does more to prevent heat loss. In fact, covering one part of the body has as much effect as covering any other. If the experiment had been performed with people wearing only swimming trunks, they would have lost no more than 10% of their body heat through their heads, the scientists add.
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Damien's note: If the above-pictured model wishes to demonstrate the findings by removing the hat and other items of clothing, I am willing, in the interests of science, to study the results.