Thanks for all the positive comments and I believe you'll get a lot from adding a form of mild cold stress to your routine activity. Over the last three years I've tried to zero in on very prescriptive methods. I'm astonished at just how deep this all goes, because I began my journey more on a crazy whim.
I don't believe you need to be miserable or extreme to have impact and there is a lot of peer reviewed literature to support this claim. In water (hight thermal conductivity/heat capacity) mild cold stress begins at about 27C/80F - hardly roughing it. At that rate if you want to consider pure heat transfer, you're at about 2.4x your RMR or for most about 250-ish watts.
That's not a huge load and animal studies that used this level had 4 hours/day - 5 days a week.
It is however a start and what happens systemically is that metabolic changes do begin to occur. If I were going to recommend one physical activity, I'd say begin swimming, but add that you should eat a nutrient dense, calorically restricted meal in the time frame of 2-4 hours after that exposure. This is a great time for cruciferous greens, fiber and colored vegetables, but leave the meats, starches, refined sugars and oils (all) out if your goal is to lose body fat. Cold exposure drives hunger and over eating will happen in this window. Without the added calorie, you'll dine on high fat love handles and thunder thighs.
As mild cold stress continues (at least as Wim Hof and I teach) you'll see greater peripheral circulation, greater sensation of well-being (CFS/depression relief), and better sleep.
As for tolerating cooler environments: gloves before sweater make you look better. Go for covering your symptoms (hands, nose, ears and toes) and leave larger areas to dump heat. Be mindful of hypothermia (especially water <60F/15C and air 32F/0C) as there is a such thing as walking hypothermia and hard cold shock can be dangerous for some. Ease in if you want to enjoy it and make it a permanent part of your life.
There's no denying that this plays a role in the hypothalamus-pituitary-thyroid axis, but no one conclusively knows yet to what degree. Every other living thing seems to respond to the seasonal cycles, we'd be a little naive to think we've evolved out of it. Wim Hof and I believe it's all quite simple: winter never comes. We still prepare, but it seems our big brain simply blew past seasonal caloric scarcity and cold stress. Both have shown great implications for health and longevity and we believe it provides some beneficial opportunities to activate these genes.
I wish I had more time to hang out here, but I don't. That being said, everyone is welcome to keep up with the latest on my site and please know that we're finishing up more academic studies in Europe now and will be offering more training coaching in the not so distant future.