Journalist Scott Carney tried out Wim Hof’s extreme cold-weather workout regimen.

Remember the line from Titanic, where Leo tells Kate that the freezing Atlantic water “hits you like a thousand knives stabbing all over your body”? Well, that’s Wim Hof’s idea of a pleasant afternoon. Often called “The Iceman,” Hof has crafted a health regimen involving cold weather exposure, intense breathing exercises, and meditation. This, Hof claims, allows him to control his body temperature, adrenaline levels, and even immune system at will, shielding him from physical danger when performing stunts like being submerged in ice for nearly two hours, hiking Mount Everest, or running a marathon in the arctic—all while wearing nothing but shorts and shoes.

He now instructs classes on the Wim Hof Method at various retreats around the world, attended by athletes looking to increase their endurance, spiritual seekers yearning for transcendence, and the chronically ill in need of healing.

When American journalist Scott Carney met Hof, his intention was to expose him as a con man. After all, this Dutch weirdo was claiming his breathing exercises and submersion in violently cold water could heal all sorts of serious illnesses. Though after only a couple of days participating in Hof’s retreat in Poland, a process that involved laying in the snow wearing nothing but shorts while hyperventilating, Carney was sold, and became one of Hof’s biggest advocates.

This conversion was no small feat. After all, Carney is the author A Death on Diamond Mountain, a cautionary tale about spiritual journeys taken to the extreme, leading to fatal injury or suicide. Charlatan gurus prescribing dangerous feats to gullible followers were Carney’s white whale, but Hof inspired the author so profoundly that he made him the subject of his latest book, What Doesn’t Kill Us: How Freezing Water, Extreme Altitude, and Environmental Conditioning Will Renew Our Lost Evolutionary Strength.

Carney has chronicled the long history of cultures around the world that embraced (or just dealt with) their skin being exposed to freezing air or water, often as a method of improving one’s health and mood. On a blizzardy Martin Luther King Day in Denver, Colorado, I spoke with Carney about his latest book, and why he continues to jog around town sans clothing in winter.

You originally traveled to meet Hof as a skeptic; what criteria were you looking for to show Hof was bullshit?
Well, I’d just written this book about gurus who claim to have superhuman powers, and how people fall into these intense spiritual paths thoughtlessly—often to their own demise. I’ve seen people die when pursuing spiritual aims over material ones.

So when I went there I expected Wim would have all these followers who infinitely trusted him, with no questioning of what he’d say; and that he’d be demanding that they give more and more control of their lives over to him. But that’s not really who Wim is. He’s actually a terrible guru. If you think about someone who might be a role model, Wim is not that. He’s a crazy guy that you would never want to be, and that’s the beauty of him. With all of his flaws—he’s disorganized, he’s a smoker, he had a drinking problem, not the epitome of human health—and yet, he has this thing, this method, and when you try it, it works.

So what are the components of the Wim Hof method?
Environmental exposure and the breathing method, which is hyperventilating and holding your breath. You learn to hold your breath for about three minutes at a time. And then you get into a cold environment and try to suppress your autonomic response systems, like your shiver response. And it’s not that shivering is bad; it’s that you want to tell your body to heat itself in a different way. Which is basically ramping up your metabolism.

Is it a case of your body getting tougher and developing mechanisms to fight off the cold, or your brain accepting the discomfort of the cold? Like the Lawrence of Arabia line: “The trick is not minding that it hurts.”
Initially, because I was unconditioned and hadn’t stood in the cold, I felt really cold, but I was showing my body the power it already had. At first your body is going to scream when you’re in the snow, because it’s not used to that stimulus, and it wants to keep you safe. So it has no gauge to understand what safe is. So you’re giving your body a little motivational push, telling it this is not going to kill us.

So do you never feel cold anymore?
There are different ways of feeling the cold. In my house I keep the thermostat around 61, and that’s enough to make me want to shiver. One of the goals of the training is to repress your shiver response. But sometimes if I’m not paying attention I’ll shiver when I’m in the house. And then I’m cold.

But if I’m doing something like running outside [half naked, in cold weather], I’m focused on not getting cold, of resisting the environment. And it’s a different set of sensations. Then I can tell that I’m cold, I can feel the sensation on my skin, but it’s almost like I’m wearing a wetsuit. It’s a very powerful feeling. So it’s all about focus.

What did you notice in your own body when going through this process?
Well, when I first started the process with Wim I lost seven pounds of fat in seven days. Which was pretty cool. I got tested at the Boulder Center for Sports Medicine during a six-month training session, and I went from primarily burning carbs in my workouts to primarily burning fat, and was able to advance a stage of endurance on their endurance test. And the only thing I changed in my workout was adding 15 minutes of breathing a day and the cold showers. And they said that was the equivalent of me adding seven hours of cardio exercise a week.

Did you ever fear for your safety or your life in this process?
Yes, I did. The method lets you expand your ability and your endurance, but it doesn’t make you impervious to the environment. It doesn’t make you invincible. And it’s entirely possible to push past your limits, and it’s important for people to be mindful of that during this process.

Has anyone died from doing this?
Yes. There have been, I think, three deaths. But they’ve all been because people are trying to mix with Wim Hof method with free diving, and that’s dangerous. Free-diving is the idea that you go really deep underwater and hold your breath for a super-long time. The Wim Hof method also allows you to hold your breath for a long time, so people think they should combine them. Unfortunately, it increases the risk of something called “shallow water blackout.”

If you faint when you do the hyperventilation, your autonomic system forces you to gasp, and when that happens under water, you drown. And that’s killed three people. And I think most of them were swimming under a frozen lake. So don’t do this under water.

I imagine it’s a tricky thing for you as a journalist, wanting to report on these treatments while being careful to not tell people they should stop seeing their doctor. 
Sure. This is a complementary treatment. I’m not saying medicine is dumb and we should all just take cold showers. Though I think Western medicine can be very myopic and drug-centric. What I’m saying is the environment you inhabit is important.

I met guys who had plum-sized joints from rheumatoid arthritis, who were basically bed-ridden, and through environmental stimulus, it was reversed. And that was inspiring. As a journalist I have to look at the evidence, and sometimes the evidence is pretty remarkable. There’s always the possibility of false hope. If people look at this and say, “Okay, I’m not going to take my chemotherapy and trust in this.” That’s just as misguided.

Do you still run in nothing but shorts in the winter around Denver? What’s the reaction?
I do. When I was doing the training regularly, I’d have all these people high-fiving me, and that’s part of the fun: Look at this half-naked guy. You feel like somewhat of a celebrity for doing something that’s totally natural.