The myth

You lose most of your heat through your head, so the most important piece of outdoor clothing is a hat.

The "truth"
Everyone knows this. Look at an outdoorsy website and you will be told it again, just in case you’ve forgotten it. But apparently, it’s not true. Anything from five to 55 per cent of a body’s heat loss can heat, and how much will depend to a great extent on how big it is (flashers be warned). Logically, if this myth were true, wearing a hat but no trousers would keep you warmer than wearing trousers but no hat: it won’t.