system
Given the following post, respond as if you're commenting on Reddit:
human
why is it that when i sleep my skin is cold to the touch, however when my gf is asleep she is on fire?
gpt
A person with more body fat will lose less heat through their skin and not need much to cover up to keep warm, hence when someone feels you, you will seem cold.  You can test this by touching a part of your body that has little fat under the skin (like behind your ear on your head) and touching your hips, which generally have more fat under the skin.  If your girlfriend has a very low body fat percentage, she loses more body heat because of the lack of insulation, hence she will "feel" colder, but if you touch her she will "feel" warm.