These days it can be shouting at alexa to set the robot off.
I can't remember what proportion goes on maintaining temperature but I think it may be about 60-70%, (Too lazy to google - saving my calories.) But you are right that it's a very large proportion.
It's a bit more complicated because it involves a the nervous system along with different organs in your body.
It also depends on circumstances, if you spend a night on a mountain in snow you will probably lose fingers or toes because your body diverts the blood to keep your brain, heart and lungs working, you can live without a toe, you can't without your brain.
My starter slide when I was teaching this was two groups of children one a group of African children in school uniform, dress or short.
The other group were Swedish children in snow suits with sledges.
We'd look at the difference, skin colour, clothing, weather and then look at what their temperature should be, the pH of their blood, etc.
I find it amazing that, with very few differences, our bodies regulate things like body temperature to within a degree regardless of where you are in the world.