I would think that there would so many chemical reactions going inside our body,friction produced by blood in veins, subcutaneous and visceral fat acting as heat insulators.
I was wondering to what extent different factors play a role in protecting our body against cold.for example say blood circulation might be responsible for creating 70% of the body heat and also a person with high blood pressure may produce more heat in his body.
also, perhaps fever or any other disease would be an exception to the normal heat creating process in our body.just like the gonads or testes which are cooler than the rest of the body.