You lose 90% of your body heat through your head.

Nope, not really. The only reason it appears so is because you lose body heat through anything that’s not covered… and your head is the most likely part of your body to be exposed. “Most of the time when we’re outside in the cold, we’re clothed,” Dr. Richard Ingebretsen told WebMD Magazine. “If you don’t have a hat on, you lose heat through your head, just as you would lose heat through your legs if you were wearing shorts.”