THE CLAIM: You lose most of your body heat through your head.

THE FACTS: "Put on a hat," parents tell their children before sending them outside on bitter winter days. While that might be sound advice, the popular belief behind it -- that most of the body's heat escapes through the head -- is misguided. The amount of heat released by any part of the body depends largely on its surface area, and on a cold day you would lose more heat through an exposed leg or arm than a bare head.

Dr. Daniel I. Sessler, an anesthesiologist and expert on hypothermia at the University of Louisville medical school, said the popular myth stems from military experiments conducted five decades ago.

Here's an interesting link: http://jap.physiology.org/cgi/content/abstract/101/2/669

and another: http://cat.inist.fr/?aModele=afficheN&cpsidt=1690440

And this quote: "both groups showed dips in temperature during surgery and recovery, but there was no significant effect of the hats alone. Conclusions: Our results indicate that the combined use of preoperative reflective hats and jackets, but not hats alone, significantly reduced temperature drop during outpatient surgery. Intraoperative reflective blankets had a small, but not significant, effect on temperature. We conclude that the prevention of intraoperative heat loss is provided by preoperative reflective hats and jackets, is not improved with intraoperative reflective blankets, and is more closely related to the total body surface area covered than which area is covered. "

Can be found here: http://www.ispub.com/ostia/index.php?xmlFilePath=journals/ija/vol6n2/temp.xml