"Cold exposure is to body composition, what passive income is to wealth -- let your body do the work whilst you reap the rewards." -- Dr Alexander Booth

The comforts of modern life have left us in a fragile state. We turn on the heater when it's cold, the air conditioner when it's hot. We pack on the layers to avoid the Winter chill. We keep our environment at a stable, comfortable temperature -- a false ideal. Such temporary comfort begets permanent discomfort -- the body is deprived of the beneficial stresses it needs to thrive, leaving us more fragile, and less comfortable as our bodies age.

Luckily, we can reverse this equation. We can manipulate our body's response to changing temperatures to improve our health and performance -- and to feel incredible. We do this through voluntary cold exposure.

What is voluntary cold exposure, and how does it work?

Voluntary cold exposure is the practice of exposing ourselves to temperatures below our comfort level to induce positive cellular responses. Physiologically, it is the manipulation of our body's mechanisms that keep us cool.

Our body needs to maintain a core temperature of roughly 37°C (98.6°F), as moving too far from this will impair our ability to function. This is achieved through the process of thermoregulation, whereby mechanisms including sweating, vasodilation (the blood vessels under our skin get wider), vasoconstriction (the blood vessels under our skin become narrower), and thermogenesis (e.g. shivering or increasing metabolism) are used to modulate our core temperature.

The body's response to cold exposure

Our bodies respond to cold exposure in two ways:

1. Insulative actions, which involve the redirection of blood flow away from your extremities. These are metabolically cheap, and are the body's first line of defence in response to cold exposure.
2. Metabolic reactions, which result in an increase in our metabolic rate to produce more heat. These reactions begin once the body has exhausted insulative actions, and needs more heat.

Stimulating insulative actions are not the goal of cold exposure, as they are too metabolically efficient to trigger the level of physiological response required to produce an effective performance improvement. We instead focus on the manipulation of* metabolic reactions*.

Our goal, as biohackers, is to use cold exposure to recruit non-shivering adaptive thermogenesis (NST). Best results are achieved when our bodies are exposed to temperatures at least 6°C below our comfort level. In response to cold exposure:

1. Our muscles increase tension (up-regulating Myosin ATPase activity) to produce heat. This response greatly increases our metabolic rate (it's why we feel stiff when cold).
2. Our mitochondria burns stored body fat, specifically brown adipose tissue (BAT), to produce heat. The amount of BAT in our body increases with cold exposure, which makes us more resistant to the cold with repeated exposure.

BAT (Brown adipose tissue)

BAT is a specialised form of body fat with a high amount of mitochondria and high concentration of thermogenin (a protein allowing heat to be produced efficiently). As noted by Dr George Bray: "... BAT activity is inversely related to BMI and percent body fat. Thus, activation of BAT may be an important component of cold-stimulated energy expenditure in adults".

What are the benefits of cold exposure?

BAT activation has a number of positive effects on the body, which we can take advantage of through repeated cold exposure. These include:

• Improving glucose homeostasis insulin sensitivity.
• Increasing bone quality.
• Improving longevity through the increased levels of (a) adiponectin (a protein hormone that modulates a number of metabolic processes) and (b) SIRT1 (an enzyme that contributes to cellular regulation).

In addition, cold exposure has been shown to have advantageous effects on our biological functions, including the ability to:

• Increase energy and alertness.
• Induce a feeling of wellbeing.
• Increase fat loss and lean muscle gain (mediated directly through the stimulation of BAT and Glut-4).
• Decrease the sensation of post injury pain.
• Accelerate healing time on acute inflammation of musculoskeletal sporting injuries.
• Improve levels of cholesterol, triglyceride and the HDL/LDL ratio.
• Improve the immune system.
• Reduce inflammation.
• Reduce muscle recovery time.
• Assist with weight loss.
• Assist with alleviating depression.
• Improve our response to stress.

Getting started with cold exposure

You've discovered the benefits of cold exposure, are psyched up, and ready to take action -- what now? Below, we'll explain some effective methods for getting started.

The goal of cold exposure is to place enough stress on the body to trigger thermogenesis. Our body's initial reaction to cold is to shiver. However, to reap the benefits of cold exposure, we must suppress this urge. This suppression triggers non-shivering thermogenesis, forcing the body to produce core heat by burning BAT -- a process that becomes more efficient with repeated use (i.e. repeated cold exposure).

"Challenges bring about the true nature within me. It alerts my body and mind, altering my state of being. It makes me feel so alive!" -- Wim Hof

Take cold showers

Cold showers feel amazing. You'll feel alive and full of energy after every session. Though the key, is to take it slowly.

I get it, you want results now: committing to a daily, 10 minute, all-cold shower sounds like a great idea --- but it isn't. All it takes is one frosty morning when you can't find the willpower to get in, for the habit to break. The strategy below is designed to remove willpower from the equation so you can maintain momentum:

1. Begin a warm shower, and slowly raise the temperature to as high as you can tolerate.
2. Mentally prepare for the cold shock by visualising the moment when you turn the shower to the coldest setting. Imagine a torrent of water flowing down an icy mountain before bursting out of the shower head. Feel the icy water hitting your skin, then see yourself taking controlled breaths as you maintain composure. The more intensity you bring to this visualisation, the easier the next step becomes -- we want to over-prepare ourselves by exaggerating what's about to happen.
3. Now we're ready. For the final 20 seconds, set the shower to the coldest setting.
4. Position yourself so the cold water hits the area around the top of the spine, as this contains the highest concentration of BAT in our body.
5. Relax into the urge to shallow your breath, and maintain a controlled cadence until you're ready to finish. Suppress the urge to shiver -- this will force your body to rely on it's non-shivering adaptive thermogenic response to maintain core temperature.

The cold will feel like needles in your skin at first, so start small. Slowly increase the duration of cold as your body adapts to the sensation, and improves its thermogenic efficiency. Beginning each shower with warm water is important to ensure compliance, as the risk of skipping the shower when willpower is low is mitigated: you are already in the shower, you are already wet -- just turn the tap. Eventually, the practice will become habitual, forming an important part of your morning routine.

Wear less clothing

This one is simple: wear less clothing than you think you need. Leave your jacket at home. Replace long pants with shorts. The goal is not comfort, it's triggering thermogenesis.

Dunk your face in icy water

This is a quick and easy method of cold exposure. It can also be used as a pathway to more advanced practices, like ice baths.

1. Fill a pan or dish with water and put it in the freezer.
2. Once the top has frozen, and the water below the surface is chilled, remove from the freezer and stir in the top layer of ice.
3. Hold your breath and put your face in the chilled water for as long as you can.

Gradually increase the time spent with your face in the chilled water over time. You can also try dipping your hands or feet into the water for further training.

Swim in cold water

Take every opportunity to immerse yourself in cold water -- visit a pool, lake or the ocean in Winter, and take a quick dip.

More resources

Podcasts

Ben Greenfield Fitness, episode #130: Tim Ferriss and Ray Cronise Explain How To Manipulate Your Body's Temperature To Burn More Fat.

Ben Greenfield Fitness, episode #187: Does Cold Thermogenesis Work For Fat Loss?

Articles

https://selfhacked.com/2016/10/19/12-reasons-embrace-cold/

http://www.marksdailyapple.com/cold-water-therapy/#axzz1s7vWHYg1

https://www.jackkruse.com/cold-thermogenesis-easy-start-guide

https://blog.bulletproof.com/cold-thermogenesis-in-tibet-and-the-dangers-of-biohacking-made-real

http://biohackersummit.com/2016/10/15/dr-rhonda-patrick-health-benefits-of-sauna/

Studies

1. Dana-Farber Cancer Institute. (2009, July 30). Scientists Create Energy-burning Brown Fat In Mice. ScienceDaily. Retrieved April 19, 2017 from www.sciencedaily.com/releases/2009/07/090729132109.htm
2. Dana-Farber Cancer Institute. (2009, July 30). Scientists Create Energy-burning Brown Fat In Mice. ScienceDaily. Retrieved April 19, 2017 from www.sciencedaily.com/releases/2009/07/090729132109.htm
3. Paddock, C. (2011, September 8). "Rich, Stimulating Environments Convert White Fat To Brown And Help Resist Obesity." Medical News Today. Retrieved from http://www.medicalnewstoday.com/articles/234094.php.
4. Berbée, J. F. P., Boon, M. R., Khedoe, P. P. S. J., Bartelt, A., Schlein, C., Worthmann, A., ... Rensen, P. C. N. (2015). Brown fat activation reduces hypercholesterolaemia and protects from atherosclerosis development. Nature Communications, 6, 6356. http://doi.org/10.1038/ncomms7356
5. Stanford, K. I., Middelbeek, R. J. W., Townsend, K. L., An, D., Nygaard, E. B., Hitchcox, K. M., ... Goodyear, L. J. (2013). Brown adipose tissue regulates glucose homeostasis and insulin sensitivity. The Journal of Clinical Investigation, 123(1), 215--223. http://doi.org/10.1172/JCI62308
6. Devlin, M. J. (2015), The "Skinny" on brown fat, obesity, and bone. Am. J. Phys. Anthropol., 156: 98--115. doi:10.1002/ajpa.22661
7. Lee, P., Brychta, R.J., Collins, M.T. et al. Osteoporos Int (2013) 24: 1513. doi:10.1007/s00198-012-2110-y
8. Kilic, U., Gok, O., Erenberk, U., Dundaroz, M. R., Torun, E., Kucukardali, Y., ... Dundar, T. (2015). A Remarkable Age-Related Increase in SIRT1 Protein Expression against Oxidative Stress in Elderly: SIRT1 Gene Variants and Longevity in Human. PLoS ONE, 10(3), e0117954. http://doi.org/10.1371/journal.pone.0117954
9. Keil, G., Cummings, E., & de Magalhães, J. P. (2015). Being cool: how body temperature influences ageing and longevity. Biogerontology, 16(4), 383--397. http://doi.org/10.1007/s10522-015-9571-2