Inside the Paleo movement there is a "cold therapy" trend. Its main contributor is Ray Cronise. You can watch a TED talk [1] and visit his web site [2]. His latest contribution is a scientific paper, co-authored with David Sinclair (yes, the resveratrol guy). It is titled "Metabolic Winter Hypothesis" [3] and it is quite interesting.
In simple terms, the rationale is the same as for the food leg of the paleo movement: Food availability is hurting us badly; warm "availability" is doing the same, so we better get some time in a colder environment.
[1] https://www.youtube.com/watch?v=UrQ_ldCwKUQ [2] http://hypothermics.com/home/ [3] http://www.ncbi.nlm.nih.gov/pubmed/24918620