How does environmental conditioning work? This, like all good questions, is simple on the surface and becomes more and more complicated each time you remove a layer and look more deeply into the heart of it. The simple answer is this: with chronic exposure to cold your body sets up mechanisms to create heat more effectively.
If that’s all you want to know then skip to the comments and thank me for saving the next five minutes of your life. Otherwise carry on …
Let’s peel back one more layer, that was just the papery brown bit of the onion anyway, it’s of no use to anyone.
When we think of generating body heat we generally think of using kinetic energy. This is the energy our body produces as a byproduct of movement. Both conscious movements, such as running and autonomous movements, such as shivering, generate this kind of heat. Our body can also create heat without movement. This second kind of heat is predominantly generated in Brown Adipose Tissue (BAT), commonly called brown fat. This tissue is found in all mammals in varying amounts.
In modern humans scientists used to think that BAT was limited to babies, but it has now been found in adults as well. Interestingly, adults who live in colder climates tend to have more brown fat than those living in more tropical climates. There is evidence that amounts of brown fat also shift seasonally.
In his book, What Doesn’t Kill Us, Scott Carney details a revelation he has during his cold training when he realized that there was a spot at the base of his neck that he could mentally push into when he was cold to release heat.
Personally I did not find this revolutionary at all. As a child of the north I have deployed this tactic for as long as I can remember to keep myself warm: on cold benches at football games, while waiting for the bus, when my brother locked me out of the house on a -40 day. I starting asking around and found that I was far from alone in this experience, many of my northern friends stumbled upon and implemented this technique as children without guidance. (Except my husband, he just looked at me as though he was concerned for my sanity … again).
Double interestingly this is precisely the spot that large deposits of BAT have been found in humans.
When we chronically expose ourselves to heat, i.e. carry out environmental conditioning, our bodies respond by creating stores of brown fat. Once you have accumulated sufficient brown fat stores you are able to withstand colder temperatures for longer periods without shivering.
Let’s take off another layer, that one had a bunch of dents in it and just looked kinda weird.
We’re going microscopic. (Don’t worry you can skip to the end at anytime. I won’t judge, but you will miss my delightful graphics).
Within each one of our cells, the very building blocks of life, there is an organelle called mitochondria. You may recall from your grade 12 biology class that mitochondria are the power plants of the cell. Inside the mitochondria chemical energy that we obtain from food (ex. Glucose) is converted into a form of energy which can be used by our cells. This new cell-friendly energy is stored as ATP (adenosine triphosphate). Heat energy is always produced as a byproduct of this reaction. (In fact heat is generated as a byproduct throughout the metabolic process. This is why you feel a quick, fleeting burst of heat when you eat a sugary chocolate bar on a cold day). This whole process is called cellular respiration.
Normal cellular respiration looks something like this (continuing to use glucose as an example):
*Not really magic, a series of chemical reactions called the electron transfer chain.
Only 40% of the energy contained in Glucose makes its way into ATP; the remainder is released as heat. When you expend kinetic energy (ex. Running or shivering) your body uses up ATP more quickly, the rate of cellular respiration is increased and heat is generated.
The ability to create heat without utilizing kinetic energy is made possible through disruption of the cellular respiration process. An uncoupling protein (called UCP-1, super original) comes in and shakes everything up. It upsets the sequence of events taking place within the mitochondria and instead of going into ATP all of the energy that is produced is released as heat. BAT contains significant amounts of this uncoupling protein. It is found within skeletal muscle in smaller amounts and is not present at all in white fat.
When the body is subject to acute cold exposure additional uncoupling proteins are recruited to the cause. When this cold exposure becomes chronic it leads to an increase in the synthesis of BAT.
The entire precise mechanism by which this process is initiated has not yet been identified, however it is known to be controlled by the sympathetic nervous system and the pathway does appear to become more heavily innervated with use.
Let’s peel back one more layer. Seriously? Now you’re just wasting perfectly good onion. Ain’t nobody got time for that. Jk, if you have time for that check out the references I’ve listed below.
If you’re as lucky as I am and live in the thriving winter oasis of Winnipeg you can tap into the expansive, underutilized resource that is Winnipeg Public Library (annual budget of $31,007,152… just saying). From their homepage go to databases – select EBSco – and you’ll have access to peer reviewed journals for free.
Still have questions about environmental conditioning? Is there something else you want to read about? Would you like more information about the resources available at the WPL? (Seriously there is so much) Comment below or connect with me on instagram @blonde.girl.hikes and don’t forget to sign up for email notifications so you won’t miss my next post.
- Carney, Scott. What Doesn’t Kill Us: How Freezing Water, Extreme Altitude and Environmental Conditioning will Renew our Lost Evolutionary Strength. Rodale Books 2017
- Cronise, Raymond J et al. “The “metabolic winter” hypothesis: a cause of the current epidemics of obesity and cardiometabolic disease” Metabolic syndrome and related disorders 2014vol. 12,7: 355-61.
- Hamblin, The Benefits of Being Cold. The Atlantic 2015: Jan/Feb Issue
- Lowell BB, Spiegelman BM.Towards a molecular understanding of adaptive thermogenesis. Nature 2000;404:652–660
- Rosenbaum M, Leibel RL. Adaptive thermogenesis in humans. International Journal of Obesity. 2010;34:S47-S55. doi:10.1038/ijo.2010.184.