I happened across this article:

http://siimland.com/ketosis-and-mitochondria

It makes the claim that brown adipose tissue (BAT) is more common in people eating a ketogenic diet. It doesn't go into how long you have to have been eating ketogenically, the rate of tissue conversion, etc.

It brought up a couple of thoughts:

1) Anecdotally, I've noticed less susceptibility to cold when in ketosis. I'd guessed that, if this was objectively true, it might be due to more efficient conversion of food to ATP or less energy going into digestion or fat storage vs generating heat (some vague and not very good theories).

2) Could this diet and its effect on BAT, rather than theories about "acclimating," have to do with better tolerance of cold in people living in the Arctic region?

Would like to see other research or thoughts on this subject, as that article up top isn't very scientific or resourced.