Cold Exposure: Is The Hype Real?

Nearly every morning for the past several years part of my morning routine has included taking a cold shower.

Yup, I voluntarily turn my shower as cold as it will go and spend several minutes in cold water year around. Remember, I live in New Hampshire and in the winter we can spend several days and weeks without the temperature getting above freezing. Once it snows here, that snow doesn’t melt until April…I ice fish for fun….that’s the environment we are talking about. In addition, my water comes from a well, a well which is surrounded by the cold outside my house. Fair to say, the water I take a shower in, particularly in the winter, is quite cold.

This past summer I even visited Dr. Mike T Nelson’s Extreme Human Performance Lab and took a dip in a deep freezer he has modified into a cold plunge.

Why would I voluntarily do this? Why do something so unpleasant voluntarily? Why make myself cold?

The idea of exposing yourself to cold environments has become quite popular lately. Cold challenges, where people take cold showers, or go into cold bodies of water, or go outside with minimal clothes on in the dead of winter (assuming it gets cold during winter where you live) have started popping up everywhere. A quick Google about the benefits of cold exposure and you can find all kinds of claims related to your health…

  • Boosts Human Growth Hormone
  • Boosts Immune system
  • Increases testosterone in men
  • Increases sperm count
  • Increases circulation
  • Reduces swelling in joints
  • Increases “brown fat” which leads to greater fat burn

Hell, there are even devices you can wear to cool you down and claim to burn massive amounts of calories!

There is also this underwear that cools a man’s testicles with claims of increasing testosterone and fertility.

Seems like getting cold is a huge win when it comes to health, but when something seems too good to be true, it is useful to take a step back and look at the science. Before we do that though, I want to tell you why I like to get cold. It can basically be summed up in a couple words…

I like the “mental win” taking a cold shower everyday gives me.

Probably the number one reason I like to take a cold shower every morning is because I like to do something hard each day. Some days getting in that shower and turning it as cold as it can possibly go is more of a mental battle than anything else. If I can conquer that mental battle and do it anyway and endure the cold, even for 30 seconds, I consider that a win. I did something hard, I did something I didn’t want to do, and that’s a great way to start my day.

Outside of the mental benefit of doing something hard each day could there be other benefits to getting cold?

One of the benefits to getting cold almost everyone knows of has to do with muscular recovery from strenuous exercise. A very common image we have seen time and time again is the elite athlete sitting in an ice bath after a hard game or competition.

In a review done on water immersion (both hot and cold) researchers came to the conclusion that immersion in 50-59 degree fahrenheit (10-15 degree celsius) water for 5-15 minutes did in fact increase recovery and allow athletes to perform better in subsequent performances [1]. The mechanisms that facilitate recovery appear to have to do with the pressure of the water and the temperature of the water (cooler being better). These mechanisms help remove harmful byproducts of intense exercise and decrease muscle soreness. As a side effect, athletes are able to perform better in subsequent exercise bouts. However, there are likely many additional mechanisms at play that facilitate greater recovery as the diagram below shows.

While these recovery mechanisms are good for athletes that need to perform optimally again after an initial competition, the same mechanisms are not so good for long term adaptations to exercise. For example, if you are trying to build lean mass or build strength, cold exposure post exercise may make you feel better and lead to less soreness, but it also blunts the strength building and muscle hypertrophy benefits you are looking for [2]. On the other hand cold exposure after endurance events does not to appear to have any negative (or positive) effects [3].

When it comes to exercise and training, your goal and adaptation you are looking for should dictate whether you should consider using cold exposure post exercise.

What about the claim that cold exposure increases fat burning and metabolism? Can exposing yourself to cold actually cause you to burn more calories and result in quicker fat loss?

In short, maybe, and if so, I am not sure it is going to be a meaningful increase in your metabolism and be something feasible for you to do in the long term.

Let’s take a step back to understand how cold exposure could possibly lead to increased fat loss. Most mammals have two types of fat in their bodies, white fat and brown fat. White fat is that fat we are most familiar with, it’s the fat we add when we over consume food and allows us to store excess calories. Brown fat is different in that it is more metabolically active, it burns more calories than white fat in order to generate heat.

The reason the fat cell is brown is because it is packed with mitochondria. Mitochondria are how cells produce energy. In the case of brown fat, that energy is used to generate heat to keep you warm.

Brown fat is particularly important in human infants as they have not developed the ability to shiver to keep themselves warm. As we age and develop the ability to shiver, we lose some of this brown fat [4].

Because brown fat has the ability to generate heat and is so much more metabolically active, if you can increase the amount of brown fat on your body, in theory this would speed up your metabolism causing you to burn more calories. If the additional caloric burn is great enough this could in theory aid in fat loss.

The question then becomes can you increase your brown fat and if so does that cause you to burn a meaningful amount of additional calories to induce a caloric deficit causing you to lose weight?

Like many physiological processes brown fat appears to be adaptive to the inputs from your external environment. In other words, if you exposed to cold long enough your body appears to increase the amount of brown fat in an effort to keep you warm [5].

So we know it is possible that cold exposure can increase the amount of brown fat on your body, but does that result in increased energy expenditure?

The other thing we need to consider is how active the metabolic processes are within the brown fat. In other words, the brown fat is only consuming calories to produce heat when it has to. Our bodies are built for survival, and since calories have been a hard thing to come by until very recently, we don’t just burn calories for the sake of burning calories. With that in mind, typically brown fat is only activated when exposed to cold, so just because we added brown fat to our bodies via cold exposure does not mean we are now burning more calories 24 hours a day.

Studies have been done to try and quantify the amount of extra calories burnt by brown fat activation and you see increases anywhere from 1-20%. Researchers have estimated that assuming brown fat could be activated maximally that it would result in burning an extra 100 calories per day [6]…that is not a lot and can easily be negated with a very small amount of food. Additionally it appears the best way to activate brown fat is via cold exposure, and who wants to be cold 24 hours a day?

I suppose this is where something like the cooling clothing I mentioned above could come in, but is that truly a viable long term solution? Again remember once the cooling stops, the additional caloric burn will go away, and eventually your amount of brown fat will decrease.

Researchers are therefore looking for other ways of stimulating brown fat. Imagine for example taking a pill that could not only tell your body to increase the amount of brown fat but also maximally stimulate it to burn the most calories possible [7]. Could this result in “weight loss in a pill”? I guess time will tell, but in my opinion unless science can somehow generate a ton more brown fat on the body, it seems unlikely.

Around this topic of caloric burn and weight loss there are some other potential benefits to cold exposure in terms of metabolic health. When brown fat is activated and generates heat it uses glucose to fuel that process [8].

This could have a meaningful impact for someone who is metabolically unhealthy and has excessively high amounts of blood sugar. Again, right now it requires activating the brown fat via cold exposure, but if an exogenous way of activating brown fat is developed that might be quite helpful for those individuals.

What about the other claims around cold exposure growth hormone, testosterone, and sperm?

Temperature can certainly affect sperm quality, volume, and motility. This study found that the optimal temperature for sperm generation was 88 degrees fahrenheit or 31 degrees celsius [9]. While that might be cooler than your body temperature, it’s not cold by any means, so getting yourself too cold could actually be less optimal if fertility is a concern.

When it comes to testosterone, this study found no effects of cold exposure on testosterone production [10]. In fact, decreased testosterone production when exposing yourself to cold after resistance training could be part of the reason why we see less strength and hypertrophy gains [11].

Finally for growth hormones, subjects exposed to 40 degree fahrenheit, 4 degree celsius, found no stimulation in growth hormone.

Ultimately I am not impressed by many of these other claims and it was quite difficult to find much evidence one way or the other for many of these claims.

So is cold exposure worth it? Should you be trying to get yourself cold on a regular basis?

In my opinion the biggest benefit to cold exposure is making you more resilient to stress and “harder to kill” by doing something difficult and doing something you probably don’t want to do. If you can teach yourself to overcome the mental battles of getting cold, think of what other mental battles you might be able to overcome! There is a lot of power to realizing you are capable of more than you think you are.

The other big benefit can be in the regulation of glucose, especially in those where their blood sugar is already dysregulated. While someone is addressing the lifestyle issues around sleep, stress, diet, movement and exercise to correct this dysregulation, activating brown fat can help regulate your blood sugar. The problem you need to overcome is the method of activating your brown fat….can you and are you willing to get cold daily?

All the other benefits appear to be minimal at best.

I should also mention at this point that like all stressors, the dose is important. Cold exposure is a stressor, adding it to a stress bucket that is already overflowing is going to have negative effects. It is not a surprise that the individual who is likely to adopt cold exposure is also the same person who is fasting a lot, exercising a ton, has a stressful work and personal life, so adding one more stressor in the form of cold, may not be the best thing for them. I have seen many people take cold exposure too far and it has shown up in their heart rate variability.

If you decide you do want to try cold exposure how should you get started?

Perhaps the easiest way to get started is to use your shower. You can start by turning it cold for 5-10 seconds for a few weeks. Over time you can slowly build up the amount of time you spend with the shower cold. Another easy option if you live in a cold climate is to go outside in minimal clothes. Maybe start your walk without a jacked and throw it on once you start to reach your limit. I would still wear hats, gloves, and shoes though as those parts of the body are quite sensitive. Once you get advanced you can consider filling up your bathtub with cold water and immersing yourself in that. Again start slow, do it for 30 seconds or so at first and extend it out from there.

In today’s world we live a relatively comfortable life from a temperature perspective. For the most part we move from one temperature controlled environment to the next never experiencing any deviations in temperature. Historically we did not have control over the temperature, if it was blistering hot, or teeth chattering cold we had to deal with it and unsurprisingly our bodies did. Reintroducing those temperature variations seems like something our bodies can not only handle, but probably expect. We may not know all the health benefits related to cold exposure at this point, but as long as you can handle the stressor, it’s probably unlikely to negatively affect you, and perhaps make you a stronger person.

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  1. (n.d.). Water immersion recovery for athletes: effect on exercise … – PubMed. Retrieved January 13, 2022, from
  2. (2015, July 14). Post‐exercise cold water immersion attenuates acute anabolic …. Retrieved January 13, 2022, from
  3. (n.d.). The Effects of Regular Cold-Water Immersion Use on Training …. Retrieved January 13, 2022, from
  4. (2018, April 20). Brown Adipose Tissue in Human Infants | SpringerLink. Retrieved January 14, 2022, from
  5. (n.d.). A randomized trial of cold-exposure on energy expenditure and …. Retrieved January 14, 2022, from
  6. (2018, December 1). Brown Adipose Tissue: An Update on Recent Findings – NCBI. Retrieved January 14, 2022, from
  7. (2020, February 4). Drug activates brown fat, improves glucose metabolism in healthy …. Retrieved January 14, 2022, from
  8. (2009, April 9). Functional Brown Adipose Tissue in Healthy Adults | NEJM. Retrieved January 14, 2022, from
  9. (n.d.). Optimal Temperature for Synthesis of DNA, RNA, and Protein by …. Retrieved January 14, 2022, from
  10. (n.d.). Effects of physical exercise and cold stimulation on serum … – PubMed. Retrieved January 14, 2022, from
  11. (n.d.). Cold-water immersion blunts and delays increases in circulating …. Retrieved January 14, 2022, from

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