The protocol involved exposing people to 60 F (15-16 C) air for two hours on day 1, four hours on day 2, and six hours on days 3-10. Although I assume they were lightly clothed, this is a pretty mild cold exposure.Here in Wisconsin, where I'm only hoping for temperatures above zero and wind chills above the negative single digits, we set the thermostat at 60° so it's interesting to hear this called "pretty mild cold exposure."
The second study went further....Egad!
.... using a longer cold exposure protocol to investigate changes in fat mass among people with low brown fat activity at baseline.... Researchers exposed volunteers to 63 F (17 C) air for two hours a day over a six-week period63° for 2 hours! 63° is what I turn the temperature up to sometimes when I'm feeling fragile.
As in the previous study, they observed an increase in brown fat activity with cold training...Cold training! Who are these people?
... and they found that calorie expenditure was higher when subjects were in the 'cold' air. After six weeks of training, body fat mass had declined by about 5 percent.Aw, come on. And these subjects were already lean! What were they doing before the study that this experiment constituted a variation?
Think about it: two hours a day at 63 degrees F.Assuming that's a lowering of the temperature. (It would be in summer. Should we power up the A/C? Or just go swimming in unwarm water? (But I heard swimming causes the body to respond with a layer of fat.))
That would seem downright luxurious to a person 100 years ago in winter in almost any temperate climate.A person 100 years ago! Here I am, right here, your person from 1914.
Today, most people keep their central heat closer to 70 F in winter, apparently eliminating a major source of passive calorie burning.If we put the heat that high in winter, the air would be stifling and we'd be lethargic and (probably) plagued with sinus infections. Now, it turns out that Guyenet is himself an advocate of keeping the temperature low, and it's because he's an environmentalist:
I use less heat because I'm an environmentalist, and because I feel that humans are meant to experience cold stress sometimes just as we're meant to experience exercise stress. The winters aren't particularly cold in Seattle, and I leach heat from downstairs, but the temperature nevertheless fluctuates between 45 and 55 F for several months of winter, with occasional excursions below 40 F.So lowering the thermostat is something Guyenet wants you to do anyway, and it's something he (and I) are already doing whether it burns more calories or not.
I've long thought that to burn more calories you ought to drink more ice water (which would include tap water on a day like today). I don't know about the hypothalamus activating the mitochondria, but isn't it obvious that your body is going to have to expend calories to warm up anything cold you put in. Now, I'm distracted by the thought of a lucrative business manufacturing smooth metal devices that fit comfortably into various bodily orifices. You chill them to some perfectly comfortably cool, safe temperature, then insert them until they warm up. Calories burned. Or, possibly, brown fat activated. Maybe the effect is greater than the expenditure of energy heating them up, if those studies mean what they supposedly mean.
I'm concerned that there's a blubber-up reaction to cold in the long term. Fat protects you from the cold. Take a look at the walrus. Nature did not evolve us to freeze to death (or to starve from over-burning our fat reserves). Our ancestors survived cold and privation to give us bodies that make us drift toward resemblance to the walrus.
ADDED: Meade read this aloud — helping me proofread — and groaned at the expression "Nature did not evolve us to...."
I protested. "This is not formal writing. It's an invention, meant to humorously resemble 'God did not create us....' I'm personifying Nature."
Meade doesn't really answer, but I type out my quote and read that to Meade to extract a response and he says "I like it" and gives me permission to quote this colloquy.
Another morning in the north, pre-dawn, getting the blogging started at Meadhouse.