How much energy does your body give off on a normal basis? Which part of your body gives off the most heat? What is this amount
Basal metabolic rate is about 75 watts. That is, this is the price of keeping a normal body temperature. Can drop some during sleep.
Light exercise -- you can talk, but not sing without excessive pauses -- raises this to 200-300 watts. A trained athlete can generate 500-1000 watts for extended periods of time.
A person has about 2 square meters of skin. Under comfortable conditions, the skin is at a fairly constant temperature. As you bundle up for colder weather, more heat is lost on the exposed bits, and less on the covered bits.
A: When under cold stress, the body shuts down surface circulation to the extremities. (Cold fingers, toes) then arms and legs.
B: Blood circulation to the head is not restricted during cold stress.
The combination of these two factors and given environments is the source of such sayings as "You lose X% of your heat through your head"
However, "if you hands are cold, put on your hat" remains good advice.