Could also be(en),undiagnosed thyroid issues.

I went just the opposite for a while. I never used to get cold. Now I'm carrying around a sweatshirt a lot.

On the other hand, without the layer of insulation, I get help warming the bed.

Yeah, even as a child I would get super cold during our mild southern winters. Especially my feet. They would be so cold they would burn. Not anymore! Now I sometimes don't even wear long sleeves. Not unusual for me to wear flip flops either.

For me, this was one of the effects of normalising my thyroid hormones. I first noticed it whilst sitting, indoors, at a workshop with about twenty people all of whom were wearing sweaters or polartec. I was quite comfortable in a short sleeved t-shirt. I also notice that when I am in a cold environment, I warm up quickly. It is so nice not to be miserably cold all winter.

I'm quite self-heating nowadays... My wife loves to use me as a bed-warmer.

Did you start excercising more? Muscle tissue keeps you warmer than fat tissue

Increased brown adipose tissue?

Art De Vany on BAT

Another summary, drawing a lot from Art, on how BAT keeps you warmer

I began low carb beginning December of last year, was braving all the worst of the Minnesota winter while in ketosis, hard to say if I tolerated it better than other years, but it certainly wasn't any worse. I had thought that fat was a good insulator, my mind has been changed in that regard at least. But is it better now? I don't know. Winters are so variable, maybe that was just a warmer winter than usual. Another winter winter will soon be upon us, another trial run. Ask me again next spring.

I do think it's no worse, at least. You always have your good days when you feel like you could brave the Antarctic, and your bad days when you just ache for springtime. I do like the youthful look of my face when I come in from a bone-cracking chill. We call it "Minnesota botox".

I used to feel really cold all the time on Paleo, when I was eating fruit once or twice a day. I replaced the fruit with fat and now I am totally fine. I boil at night (which is odd), but for the most part I am no longer wearing two pairs of pants!

I'm less prone to feeling cold at night.

Last year, I rode my motorcycle through to the first week or so of December, at which time the temperatures were simply too cold to bear. I'm curious to see if I can tolerate the temperatures for longer this year.