Taking the Ice Tank Plunge: What is “Cold Thermogenesis”?
Basically you voluntarily plunge into ice tanks. Regularly.


Winter in Chicago: It feels like living in an ice tank. Metaphorically, of course. Unless you practice “cold thermogenesis”…in which case, you voluntarily plunge into ice tanks. Regularly.

Have you heard of this Tim-Ferris-approved fat-burning sensation? Or the fat-freezing fanny packs? Is it true this cold-exposure technique can transform metabolism? Here’s our roundup of the cold, hard facts.


Cold thermogenesis hinges on the idea that regular exposure to cold temperatures will increase metabolism. Proponents believe when your body senses potentially life-threatening cold, it increases the rate of cellular activity to raise the core temperature. This in turn burns more fat calories and increases metabolism.

The Two Schools:

Dr. Jack Kruse, neurosurgeon and CEO of Optimized Life, advocates for full body ice baths and extreme air temperatures (like walk-in freezers). His method begins by submerging your head in ice water to activate the mammalian diving reflex. He makes highly sensational and persuasive statements (“A 26.2 mile marathon burns 2600 calories. My three hour training session I did this AM burned 3800 calories.”), although his method has only been verified by self-experimentation and customer testimonials.

Ray Cronise, former NASA scientist and founder of Thermogenex, supports a less extreme approach. His chapter in The 4-Hour Body advocates cold showers, swimming in cool water, and lowering your house thermostat to increase cold tolerance. In this TEDMED Talk he says, “it doesn’t have to be extreme” (7:04). Cronise is currently working on more definitive clinical trials at his home laboratory.

What We Know About Cold Thermogenesis and Ice Tanks:

We’ve discovered “brown fat”

We have two types of fat cells: brown and white. Brown fat, known as “brown adipose tissue” (BAT) is a powerhouse of energy-producing mitochondria and oxygen-consuming capillaries. When brown fat breaks down it releases enormous amounts of heat.


Brown fat could speed up weight loss

Until now, scientists believed brown fat was found only in newborn babies but was lost as we age. But recent studies have found BAT in adults, and effectively linked fewer brown fat cells to obesity. This study in rats found that cold exposure increased brown fat oxygen consumption by 450%. And another study found cold exposure increases BAT energy production – leading to increased metabolism and fat loss.

Stuff we don’t know about ice tanks:

Which variables matter?

How long should you stay in the ice bath?

Does BMI matter?

How does age or gender affect outcome?

Steve Leckhart of WIRED magazine reported, “There’s not much rigorous science behind any of this. Studies have shown cold exposure can boost the metabolism anywhere from 8 to 80 percent.”

Leckhart met with Ray Cronise to undergo a cold thermogenesis trail at his home laboratory. Cronise’s measurements showed Leckhart continued to burn fat “for 30 to 40 minutes after he got out of the water.” Was it shivering muscles that burned those calories, or brown fat? “For now there’s no way to know.”


The Danger of Ice Tanks is Real, Yo

Yale Professor Dr. David Katz, told ABC, “Exposure to extreme cold could lead to a cardiac event in those at risk.” The cold shock of ice baths specifically, “can affect blood flow to vital organs, blood pressure, or induce cardiac arrhythmias.”

Which is exactly what happened to The Bulletproof Exec’s Dave Asprey. He recounts,

“My previous attempts at cold exposure were not fruitful…Cold showers tended to be so shocking that I felt awful after them for hours. One time it even induced a double heart beat, which is uncomfortable but not dangerous.”

And when he didn’t follow Dr. Kruse’s protocol – the ice gave him first degree burns all over his body. Hot damn. (Here’s the full blog on his first experience.)
And here, he provides the trick to get into Cold Thermogenesis. Listen to your body but also have an open mind going into your first ice bath or cold shower. Your mentality will help!
So, the jury is still out. But it’s encouraging to think Chicago’s miserable winter weather may be giving us a metabolism boost. What do you think? Is that enough incentive to lower your home thermostat?

Have you 75ers had luck with CT training? Let us know in the comments below.

And for you cold weather enthusiasts, here are some recommended winter workouts.