called non-shivering thermogenesis, which is when your
body warms itself up to protect against heat loss. Your body
does this by ramping up calorie burning in the power-
generating mitochondria of brown fat. This is a type of fat
that we actually want more of because it promotes better
metabolic health. Brown fat is so keen on burning off
calories that non-shivering thermogenesis can account for
up to 40 percent of your metabolic rate, making it a
powerful form of exercise you can do without even moving!
In one shining example of the hormonal benefits of cold
exposure, people with type 2 diabetes were told to endure
six-hour-per-day exposure to mild cold (60°F). After a mere
ten days, they improved their insulin sensitivity by a
whopping 40 percent.^16 You may recall from chapter 4 that
insulin sensitivity is highly correlated to better brain health
and brainpower. Other studies have suggested that
thermogenesis (calorie burning in exchange for warmth) and
metabolic benefits can occur at an even milder temperature
—66°F.
If the thought of being even remotely chilly makes you
reach for the nearest blanket, take comfort: the more we
expose ourselves to cooler temperatures, the more health
benefits we stand to gain. And these benefits increase even
as we mentally adapt to the cooler temperatures. So, next
time you’re standing by your thermostat wondering what to
program, keep in mind that chronic climate comfort may be
in the same league as sugar when it comes to metabolic
mayhem.