I suspect it's a combination of the percentage of body fat and circulation slowing. I lost weight very quickly due to a medication and really feel the cold more now too. I wear layers inside! The good thing is when I go out and do any activity, I like to work hard, and that generates enough heat to warm me up thoroughly. Although we don't regularly get down to 0f . . today was 25f 30-40 mph wind gusts . . the blizzard dumped nearly 2' of snow here . . I was shoveling like a maniac, and got so hot I took my jacket off.