They say that necessity is the mother of invention.  In considering the health benefits of being cold, James Hamblin, M.D. describes the need of former NASA scientist Ray Cronise to lose weight:


During the swimmer Michael Phelps’s 2008 Olympic gold-medal streak, Cronise heard the widely circulated claim that Phelps was eating 12,000 calories a day. Having been fastidiously trying to lose weight, he was incredulous. Phelps’s intake was more than five times what the average American eats daily, and many thousands of calories more than what most elite athletes in training need. Running a marathon burns only about 2,500 calories. Phelps would have to be aggressively swimming during every waking hour to keep from gaining weight. But then Cronise—who knows enough about heat transfer to have been employed keeping astronauts alive in the sub-zero depths of space—figured it out: Phelps must be burning extra calories simply by being immersed in cool water.


Cronise decided that being cold was the ticket to weight loss:

Fascinated, Cronise began a regimen of cold showers and shirtless walks in winter, and he lost 26.7 pounds in six weeks. He began measuring his metabolism during and after cold exposure, and found that his body was burning a tremendous amount of energy. Rather than storing energy as fat, his body was using it to sustain his core temperature. Cronise’s preliminary experiments led him to put together what is now a pretty high-tech lab in his Huntsville, Alabama, home, where he conducts miniature scientific studies, mostly on himself.


Hamblin explains that being warm most of the time is a fairly recent phenomenon in the human condition.  And so is diabetes, and obesity, and other metabolic disorders:

Cronise, Bremer, and Sinclair propose what they call the “Metabolic Winter” hypothesis: that obesity is only in small part due to lack of exercise, and mostly due to a combination of chronic overnutrition and chronic warmth. Seven million years of human evolution were dominated by two challenges: food scarcity and cold. “In the last 0.9 inches of our evolutionary mile,” they write, pointing to the fundamental lifestyle changes brought about by refrigeration and modern transportation, “we solved them both.” Other species don’t exhibit nearly as much obesity and chronic disease as we warm, overfed humans and our pets do. “Maybe our problem,” they continue, “is that winter never comes.”


Read more of how this idea launched the invention of an ice vest, “The Cold Shoulder” — a “Han Solo-type of garment loaded with ice packs” that harnesses the forces of thermodynamics and helps lead to weight loss here.  (Or, just open a window and stay chilled — just like a caveman.)