Apparently adaptation, I read an article about a cold weather research project, people were adapted to cold in about three weeks, one of the participants said that it was the most miserable time of his life. It also is "use it or lose it".So, again, is it adaptation, not evolution ?
Cold weather is also one of the easiest way to lose weight, dress lightly and do some aerobic exercise like walking (without sweating!) 5h a day, eat as usual and lose 1kg a day. It also helps if one sleeps outside. (Tested that in Norway on a fishing trip, something of a surprise, I really did not have the need to lose weight at the time.