The book reveals how environmental conditioning can improve your health by boosting your metabolic efficiency. A large portion of the book focuses on Dannish fitness guru Wim Hof's philosophies.1
Hof does not lead a healthy lifestyle and does not optimize his diet or other healthy lifestyle strategies, which makes these accomplishments even more impressive. Please understand this interview is not an endorsement of Hof's lifestyle.
Hof, perhaps better known as "The Iceman," has gained a fair amount of notoriety for his ability to withstand extreme cold — an ability he attributes to a specific set of techniques involving breath work and extreme temperature conditioning.
Conquering Mount Kilimanjaro
Carney was initially hired by Playboy Magazine to investigate Hof, but wound up embracing this program, and actually climbed Mount Kilimanjaro, the highest mountain in Africa, wearing nothing but shoes and shorts, going shirtless most of the way.
He also completed the climb in 28 hours, which is very fast. It usually takes five to 10 days to get to the top, as you need to acclimatize to the altitude. Altitude sickness occurs when your blood oxygen level gets so low that you start having headaches.
As it progresses it can turn into hypobaric hypoxia, which leads to swollen limbs, cardiac arrest and pulmonary embolism. Ninety percent of people who attempt the summit get some version of altitude sickness.
Carney's training allowed him to make the climb without acclimatization, which is nearly unheard of.
From Skeptic to Believer"The U.S. Army Research Institute of Environmental Medicine, which is the environmental unit for the U.S. army, has really advanced tables for high altitude ascents. They predicted about 70 percent [of the group] would come down with acute mountain sickness ...Instead, 93 percent of us made it up to the top. The first group, where I was, did it in 28 hours, which was incredibly fast. When we asked the Dutch Mountaineering Association what our success rate would be, they predicted a 100 percent fatality rate," Carney says.
That's a powerful testimony to the physiological benefits of the strategies Hof teaches. Ironically, Carney actually approached Hof as a skeptic, intent on debunking his methods. He thought Hof may be harming people with his advice. Carney explains:
Carney met Hof in Wroclaw, Poland, in the middle of the winter, and Hof confidently stated that, within a few days, Carney would be standing outside in the snow wearing nothing but his shorts, feeling comfortable and warm."I'm an investigative journalist. Over the course of my career, I have examined a lot of false gurus, people who make really advanced spiritual claims and occasionally end with people dying, getting hurt, losing all their money — that sort of thing ...When I heard about Wim Hof, I thought he was going to be another very sketchy guru ... because his claims were that he could control his body temperature at will, consciously control his autonomic nervous system and his immune system ...He has the record for an Arctic marathon, barefoot in his shorts. He's done marathons in the Sahara. He's hiked two-thirds of the way to Mount Everest, also in his shorts. I knew he had some of these abilities ...However, what I worried about was that he was capitalizing on innate biological abilities, and made false claims that they were teachable. I worried he could get someone killed."
"I thought that was sort of crazy," Carney says. "But as an anthropologist, as an investigative journalist ... I can't just go there and write him off full stop without giving him a chance." As it turned out, Carney became an enthusiastic convert.
Tapping the Human Potential
The first thing Hof teaches is a breathing method that involves intermittent deep breathing and breath-holding after the final out-breath. In short order, Carney, who could normally hold his breath for about 30 seconds, was able to hold his breath for two minutes without air in his lungs.
Another breathing method involves intermittent hyperventilating, followed by a breath-hold after the final out-breath while you do pushups.
Suddenly, Carney's ability to do pushups doubled — from 20 pushups to 40, all in a matter of 15 minutes' worth of breath training. Carney describes the rest of his remarkable journey:
By Avoiding Temperature Extremes, You Forgo Health Benefits"I thought, wow, Wim has figured out something about the body that is really, really interesting [so] ... I said, 'OK. I'm going to give his whole shirtless [in the] snow thing a chance.' I stripped off all my clothes. Basically, I'm in my underwear.I walk out and I put my feet in the snow for the first time. He's like, 'You're going to stay out here for five minutes.' I'll tell you what. It hurt. We're probably talking 25 [degrees] F ... I put my feet in the snow and it felt like walking over hot coals.What's happening there is you're triggering this response in your body called vasoconstriction where the arteries in your feet will [close] to push the blood to the core ... In five minutes, it was super painful. Then we jumped into a sauna right after that.The process of vasodilation, which is where your arteries open up, that hurt even more. I was like, 'Wim, this is a terrible method. Why are you teaching this?' He's like, 'Yeah. Of course, it's going to hurt. You've never done this before. But just wait until tomorrow' ...The next day, I was standing out in the snow and that feeling of panic and pain didn't set in for 10 minutes, which is like doubling my resistance in [one day]. We just kept on doing this for a week. We're jumping in cold water. We're rolling in snow ...By the end of the week, I'm standing in the snow in my shorts, sweating in this Polish winter. I'm there for an hour and there's no problem. At the end of that journey with him, I hike up a mountain in Poland, again, wearing just shorts in the middle of the blowing winter.We're talking about 2 [degrees] F. I'm on the mountain for eight hours and I just sweat the whole time. I knew that whatever Wim was doing, it worked ... I had to reevaluate what I thought about these sorts of gurus who have these ideas that seem so impossible.I realized Wim wasn't offering superpowers. He was offering human powers ... Humans have an innate ability to adapt to the environment around us. All he was doing was giving me a method to learn how to control some of these processes in my body."
One of the primary premises in Carney's book is that our technological sophistication, which allows us to live in a very climate-controlled situation within a narrow comfort range, impacts our health in surprising ways. For most people alive today, climate-controlled comfort has been the experience throughout our life, and we have no reason to believe that exposure to harsh conditions might be beneficial.
But, according to Carney, the evidence suggests the human body actually needs those extreme temperature variations. We evolved to develop resilience and health through those changes. For example, vasoconstriction and vasodilation help optimize the function of your circulatory system by strengthening all those smooth muscles that allow constriction and dilation to occur.
Why Cold Thermogenesis Improves Health"What this means is that we have all of these muscles in our circulatory system that just aren't getting exercise ... [T]hat guy with the gym body ... may look physically healthy, but actually [may] have a fairly degraded arterial system, just because he hasn't stimulated it. We need this external stimulation to live a full human life and really use all of our biology.There are serious autoimmune impacts with this — treatments for diabetes, obesity and all of these things that are important because we used to think that human health relied on diet and exercise ... But what this book uncovers ... [is] that there's actually a third pillar. The third pillar is the environment ... If you ignore it, you're not doing your biology any favors."
One of the mechanisms by which cold exposure or cold thermogenesis aids weight loss and reduces your risk of diabetes and other chronic disease is by inducing brown and beige adipose tissue (BAT), which is incredibly mitochondrial-dense and helps improve mitochondrial function. One of the physiological functions of body fat is to be used as fuel to heat your body if you have active BAT metabolism.
By regularly exposing yourself to cold, you build up a mitochondria-rich tissue very similar to brown fat called beige fat. Beige fat is recruited through your white fat, which can then be used to heat your body and maintain a more active-passive metabolism. Indeed, the conclusion I reached after many decades of studying health is that burning fat as your primary fuel is the goal.
There are a number of ways to reach this goal. You can do it through diet, and in my new book, "Fat for Fuel," I explain how to do that. But there's also a tremendous synergy with cold thermogenesis.
The good news is, we all have this latent capacity that we can tap into and relearn. It went underground, so to speak, but it didn't disappear. Carney developed remarkable endurance to cold in a single week. He also lost seven pounds of fat in that same time."Western civilization has given us this enticing option of being comfortable all the time. We just think, because we're so technologically advanced, that comfort should be available at the flip of a switch. But that's actually undermining who we are as people and leading to things like obesity, weak circulatory systems and ... autoimmune diseases," Carney says.
Getting Started at Home
A simple way to improve your BAT metabolism is taking cold showers. The initial tensing is part of your body's attempts to heat itself back up. Try to suppress this initial instinct and relax instead. As noted by Carney, "What you're doing is telling your body, 'OK. We're not going to do the easy method, which is use our muscles to heat ourselves. We're going to turn on our metabolism.'"
A more effective strategy would be to swim in cold water, which may be a relatively easy strategy for many to implement during winter months. You want to start slowly around 70 degrees or so and gradually work your way down to the 40s. It is not necessary to swim in ice water.
I tried this last year and was amazed that initially 62-degree water would cause me to shiver but after sticking with it for a few weeks to months I could comfortably swim in mid-40-degree water. My only problem is that my ears would get cold.
How long it takes to build up BAT is still unknown. But we do know that BAT is generally a seasonal tissue. In the winter, your body generates more of it. In the summer, you have less. A primary issue is, how often do you activate it? Without environmental stimuli, your body will not create this metabolically or energy-rich tissue, as there's no reason for it to do so.
In addition to ice baths, you could simply turn down the thermostat in your house in the winter to about 60 degrees F. Jumping into cool or cold water after heating up in the sauna is another strategy I've been using. Exercising in cold weather wearing few articles of clothing is yet another strategy. As noted by Carney, "What you're doing is you're giving all of these signals to the nerves on your skin to say, 'Hey, it's winter. Now, let's start generating BAT,' because that's what your body does.""Maintaining it by taking cold showers, ice baths or just giving variation in your routines is very important if you want to have these abilities. How long does it last if you don't do it? I don't know and I don't want to find out personally. I am pretty excited about having it and having these abilities, and it's not very difficult to maintain," Carney says.
Breathing Methods Speed Up the Process
Carney recommends incorporating Hof's breathing methods as well, although it's worth noting that this is not for everyone. Since it involves hyperventilation, people with anxiety or who are prone to panic attacks would be wise to make sure you're learning such breathing techniques from a competent teacher who can address any psychological reactions that may crop up.
Breath holds are also not good for everyone, and may be unhealthy if done recklessly. Breath retention practices taught in yoga, for example, are done in a very careful and calculated way, and for good reason. If you want to try it, be sure you understand the instructions, start off slow, and build your ability over time. It's important to understand that hyperventilation can cause adverse psychological effects, and could make you pass out. So, please, act responsibly and practice safely.
Also, never, under any circumstance, perform breath-hold exercises under water, as you may black out and drown. There are in fact reports of people dying from this kind of practice, so always be mindful of your safety, and make sure you have a spotter — someone who can help you should you get light-headed or dizzy.
With those warnings in place, the breathing method Carney recommends can be briefly described as follows: First, you take 30 to 40 deep controlled breaths. This will decrease the carbon dioxide (CO2) in your system and increase your oxygen (O2) saturation up to 100 percent. Next, after a complete out-breath where you've emptied your lungs as completely as possible, you then hold your breath until you get to that point where you need to gasp for air.
Unfortunately, Hof neglects to mention the many others that have adopted these techniques prior to his popularizing them. There's a similar type of breathing called holotropic breathing, developed by Dr. Stan Grof. Hof also teaches another method called DMT breathing, which is virtually indistinguishable from holotropic breathing. Yogic breathing or pranayama is another similar technique, as is the Tibetan breathing technique called Tummo, which allows you to consciously control your body temperature."By doing that, you're interacting with an autonomic system in your body, which is where the gasp reflex is. You're telling your body that you should have some control over this system," Carney explains. "It's the same thing that you do in a cold shower when you're telling yourself not to shiver. It's the same skill of becoming mentally strong over an autonomic reflex.These two methods work on different systems, parasympathetic and sympathetic systems, in the body. What that does is give you more resistance in the cold and has this autonomic trick, this autonomic ability to influence your immune system down the road, which is incredibly useful."
Brazilian Jiu Jitsu legend Rickson Gracie also uses yogic breathing for cold resistance and mental strength. Ice bathing, sauna and the combination of the two also have a long history and tradition in Russia and Scandinavian countries. So, what Hof is teaching is nothing new. Many of these techniques have been around for a long time. What makes Hof particularly interesting is his openness to investigation and testing, giving us a deeper insight into our human potential.
Implications for Autoimmune Diseases
This kind of extreme environmental conditioning and breath work also has an impact on your immune system. Hof claimed he could consciously control his immune function, which at that point was defined as impossible by science. A Dutch immunologist named Peter Pickkers, who's renowned for developing a clinical test to evaluate the effectiveness of immunosuppressive drugs, decided to investigate Hof's remarkable claim.
Hof claimed he could suppress his immune system, effectively making his own mind do the work of an immunosuppressive drug. The test Pickkers developed is called the "endotoxin test", which is essentially injecting E. coli bacteria that have been killed in a laboratory to see if the immune system responds. Normally, when you're injected with this bacterium, you will have an immediate primary immune response. If the immunosuppressive drug works well, then you won't have those symptoms.
Hof was injected with this endotoxin and using nothing but his breathing method, he had no response other than a minor headache. "This was a really big response because it had never been shown in a clinical setting that you could do this," Carney says. Tests confirmed his blood was indeed resistant to endotoxin. Even after blood had been removed from his body and placed in a container for six days, it continued to be resistant.
Notes on Safety"This was a very interesting study. The medical community said, 'Well maybe it's just because Wim is a freak,' which is a totally good point to make ... [So] the next year ... he took 12 volunteers from Holland and brought them to Poland to give them the exact same training that I got ... took them back to the Netherlands [and] injected all of them with the same endotoxin. All of them repeated the same results.This was published in a very prestigious journal called the Proceedings of the National Academy of Sciences. It's a huge study. Because if ... you can consciously suppress your immune system, this has potential impact for every autoimmune illness out there ... anything where your body is attacking itself.Think arthritis, lupus, Crohn's disease. To some degree, diabetes [and] Parkinson's. All of a sudden, all of these people are starting to use the Wim Hof method to treat themselves for a huge variety of autoimmune illnesses.In the book, I look at four case studies of four different people who are using cold showers and conscious breathing to combat and reverse, in some cases, Crohn's disease, arthritis and Parkinson's. There are amazing anecdotes. This is not a totally randomized, placebo controlled study that ha[s] gone on for 15 years, but they're great leading edge results and they are real people. I've seen them myself," Carney says.
I would be remiss were I not to mention the importance of training within your limits, ideally with a qualified trainer, should you embark on more extreme temperature and breathing challenges. The reason for this is because there are risks involved.
When exposing yourself to extreme cold, you have to be mindful not to stay cold too long, as hypothermia is a very real concern. Additionally, rapidly heating the body when hypothermic, or near hypothermic can be very dangerous. In fact, it can be lethal. Carney explains:
More Information"It's called the afterdrop. It's actually a potentially dangerous situation. Like if somebody's stuck under the ice in a lake and has hypothermia, you don't want to warm them up quickly by putting them in a warm shower. This is because vasoconstriction constricts all of the blood to your core to keep you alive and warm.Then when you warm up, there's the opposite, which is vasodilation, where it opens up and recirculates that warm blood through the limbs. But if your limbs are very, very cold already because you're hypothermic ... the warm blood in your core will circulate to your cold limbs and then return cold blood back to your core. Your core temperature will drop precipitously.If you find somebody who's actually in dangerous hypothermia, if you warm them up too quickly, their core temperature will drop and they'll die. They'll have a cardiac arrest. While doing these trainings, you do risk, to some degree, having a minor level of that afterdrop, especially when you're first starting out, before you're really teaching your metabolism to deal with this.One thing you can do to combat afterdrop, as long as you're not too [close to] hypothermia — which you should never [be] because you should always be practicing within your limits — but you can do an exercise, such as pushups, such as running ... Use your muscle movements to bring your core temperature up. That will do it safer."
If you're intrigued by the possibilities presented here, pick up a copy of "What Doesn't Kill Us." "Just give it a chance ... Even if you don't read the book, try a cold shower. That's the base. That's the total minimum. If you do want to examine the book, it's on Amazon. It's on Audible ... I've been so happy that I've affected so many people's lives so far. That's awesome," Carney says. You can also find out more about him at scottcarney.com
I believe it has the potential to help many. This kind of environmental conditioning — heat and cold stress — is a really powerful health principle that very few clinicians appreciate, but it has many important metabolic benefits. I heartily endorse and personally embrace and practice it.