Scott Carney knows all about immune system hacks. The anthropologist and investigative journalist set out in 2011 to prove that Wim Hof, affectionately known as “The Iceman,” was a charlatan. Instead, Carney discovered that Hof’s breathing techniques and cold-exposure therapy cured him of longtime ailments. The writer even hiked to the top of Mount Kilimanjaro alongside Hof wearing just a bathing suit. His adventures resulted in the 2017 best-selling book “What Doesn’t Kill Us” (Rodale Books, January 2017).

Carney’s new book “The Wedge: Evolution, Consciousness, Stress, and the Key to Human Resilience” (Foxtopus Ink) will be published in April. While he considers this a sequel to his book on Hof, Carney investigates more techniques for achieving optimal health and boosting your immune system. I recently chatted with Carney about his latest effort, which you can listen to here. Below are six hacks that Carney covers in his excellent new book.

Breath work

Since most processes that control your body’s homeostasis are autonomic, we tend not to pay close attention to them—until something goes awry. But there are great benefits to learning how to breathe better.

Breath control is necessary for cold exposure. Carney has spent years practicing variations of Hof’s techniques (including breath retention). It turns out that such techniques have wonderful effects on your nervous system. As Carney writes, down-regulation (parasympathetic tone; relaxation) correlates with higher CO2 levels in the blood, while up-regulation (sympathetic tone; excitability) means lower CO2.

Carney visited performance expert Brian Mackenzie, who uses CO2 retention as a means for giving the body an extra boost when needed (as in competition). According to Mackenzie, most people breathe about 20 to 25 times per minute while mindful breathers average about 10. Importantly, most people breathe through their mouths, which activates sympathetic tone; nose breathers (as in yoga) activate sympathetic tone. By learning how to master breathing, Carney writes, “you can control your physiology.” More sympathetic tone equals a less reactive nervous system, leading to increased immune response.

Cold exposure

“I spent 10 years trying to perfect control of my body temperature in cold environments,” Carney says. “There’s this big immune boost that goes with it. It’s a very stressful environment that really jacks up your adrenal response. What you’re trying to do when you’re in that ice water is not shiver; you’re trying to relax in this very stressful environment. You’re using your mind as a wedge between stimulus and response.”

While modern conveniences are wonderful, there’s always a trade-off. Indoor climate control has resulted in an inability to weather temperature variability, which our ancestors contended with for 350,000 years. While some research backs up the benefits of cold showers and immune response (with more underway), most reporting is anecdotal.

Cold-exposure advocates tout the mental fortitude of the experience. The anticipation of discomfort, Carney says, is always worse than the actual experience. Struggling (and even relaxing) in a stressful environment provides valuable mental training. As with any protocol, caution is warranted. Begin with a cold shower because that you can easily control.

Heat exposure

Carney also explores the other extreme by spending time in the sauna. Before the widespread distribution of pharmaceuticals, hot springs and saunas were commonly prescribed. In many European countries, they still are.

Carney visited psychiatry professor Charles Raison, M.D., whose research has shown that heat therapy matched ketamine in efficacy for treating depression. Raison points to inflammation, which researchers are realizing is a primary driver in both anxiety and depression. Saunas help reduce bodily inflammation, resulting in improved mental health while giving your body an immune boost.

The Potato Hack

Imagine eating nothing but potatoes for five days. You can cook them and even add a pinch of salt and pepper. No butter, no oil, however. Sound good?

“The potato hack was really about trying to understand how taste frames my world,” Carney says. “All of us are emotional eaters. Our Paleolithic ancestors had to eat to survive. There was always this calorie deficit that they were coming up against. In the modern world, we have the opposite of a calorie deficit—we have an overabundance of calories, but we still have that Paleolithic response to food that triggers your pleasure centers. Every food marketing company in the world knows this.”

More than half of Americans eat over the course of 14-plus hours a day. If you first put something in your mouth at 7 a.m., that likely means you’ll continue to consume after 9 p.m. Much of that eating is, as Carney says, emotional. You don’t need those calories. Not only are snacks stored as visceral fat (since you haven’t digested your last meal), but we also form emotional bonds to foods high in sugars and carbohydrates.

If you average 2,000 calories a day, potatoes will give you the same sense of satiety with around 800 to 1,000 calories. Heavy in “resistant starch,” potatoes pass through your digestive system without adding calories, putting you in a deficit. While there are weight-loss benefits, this hack is only designed to last three to five days. The real benefit comes from giving your system a break. Carney points to evidence that potatoes also re-balance the gut microbiome, which is an obvious bonus for your immune system.

Sensory deprivation

“You have all these sensations that you’ve experienced that trigger emotions,” Carney says, talking about his time in sensory deprivation tanks, “then that’s how you experience the present moment. Most of what I’m doing in “The Wedge” is putting myself in really intense stressful situations and then trying to control my reactions. But what happens when you take the body completely out of the environment and as close to just floating in nothingness as possible?”

What happens, he points out, is an emotional reset that’s proving helpful to trauma victims and post-traumatic stress disorder sufferers. Float tanks can interrupt the cognitive and emotional loop that happens in quiet times and allow people to form new associations with their thoughts. Interestingly, when we feel as little of our body as possible, we forge a new mind-body connection.

Chronic stress associated with traumatic events keeps victims on guard at all times, even if unconsciously. One of the worst scenarios for anyone’s immune system is chronic stress. Float tanks might offer hope where other interventions do not, allowing the possibility of resetting cognitive loops naturally through complete relaxation.

Kettlebell passing

When Carney heard about a man who tosses kettlebells as a means for focus (and fun), he had to check it out. He hopped on a plane from Denver to Northern California to meet up with Michael Castrogiovanni, a kettlebell trainer who helps people enter flow states through the intense focus needed to not drop a ball of iron on your foot.

“The really fascinating thing about kettlebell throwing is that the movements are not incredibly hard,” Carney says. “It’s actually fairly easy to learn in 15 minutes. Someone can teach you how to throw a kettlebell, but that sensation of fear of possible danger is always going to be there.”

This highlights one of Mihaly Csikszentmihalyi’s requirements for flow states: an attainable level of challenge. Too easy and you tune out; too challenging and you give up. As the kettlebell flies through the air, you have to be locked into the arc of the bell and the posture of your partner.

As Carney notes, it’s really not about a fitness workout as much as a trust exercise. Fitness always requires some level of tension. As it turns out, tossing kettlebells back and forth uses that anxiety for a positive benefit, coopting the physiological response of stress as a team-building experience.

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