A while back we got a comment from Robin:

“I would appreciate you guys weighing in with your opinions and/or evidence regarding cold thermogenesis. CT as it’s called seems to be all the rage on Sisson’s Primal site these days. There are people taking ice baths and putting ice packs on their tummies, etc.

Many there are citing Tim Ferris as the ultimate authority on CT along with Ray Chronise and Jack Kruse.

Is there any merit in this or all just the latest fad?


I got a little more info from Robin through email about people taking hour-long ice baths and possibly developing an unhealthy obsession with the pain and discomfort associated with the practice. This, people, is why I don’t hang out on internet forums or blog comments sections. In all but a few rare cases, for every tiny nugget of useful information you have to read through pages of idiocy, trolling and keyboard cowboying.


On to the point… cold thermogenesis: is it useful for fat loss?

I was gifted a copy of Ferriss’s Four Hour Body by my friend Greg (who has his own cool project going on) and in it he (Ferriss, not Greg) recommends either ice baths or ice packs on the upper back/neck area. I haven’t read through Kruse’s site, but I have read through most of Cronise’s site and I think he’s got the best over-all take on the whole thing, but because of his approach I don’t think there’s a whole lot for him to talk about – this is a good thing. More on that later.


A Very Basic Explanation

The idea behind CT is that by exposing your body to cold, you employ its ability to burn fuel in an attempt to warm itself. You can see how this raised metabolic state could aide in fat loss – because calories count, right?  And if you can raise the amount of calories on the ‘out’ side of the equation, it’s all good in the ‘hood.

In recent years researchers have discovered that something called brown adipose tissue (BAT) is present in adult humans (Really, this had been known for a while but sort of misplaced). Until then, it had been identified in other species and in human infants, but scientists thought that by adulthood we had lost our brown adipose tissue. As things often go, we developed more sensitive measurement techniques and presto, there is brown adipose tissue in adult humans in a few places in the upper body.

Why is this important? Well for our discussion it’s important because BAT burns calories to create heat, thanks to a little guy called uncoupling protein-1 (UCP-1) which allows the mitochondria to burn through fuel at alarming rates. Notice that BAT is located in a convenient place to keep our core warm during cold exposure. This is important as well. We’re going to think of BAT and our muscles combined as a furnace, with its thermostat somewhere in the brain. When our core temperature starts to drop, the thermostat kicks the furnace on and we heat up the core and to a lesser degree, the rest of our body.


The Dunk Tank

So, people are taking cold baths. Let’s do a quick run-down of what can be expected from a metabolism point of view. Skin temperature will drop to adjust to within about 1 degree C of the temperature of the water. Core body temperature will start to drop and at some point the thermostat will decide it’s dropped enough and it kicks the furnace on. The furnace starts burning fuel to create heat and will continue to do so as long as the core needs heating. Once the stimulus is removed, your body will heat up and the thermostat kicks the furnace off.

While the furnace is on, metabolic rate can double or more. In one study where subjects entered water 22 degrees Celsius and below, metabolic rate adjusted from 2 kcal/min to 5 or 6 kcal/min. (Cannon 1960) If you’re taking a 20 minute bath that equates to a burn of 120 kcal instead of 40 kcal, or a net boost of 80 kcal. This is for 20 minutes of exposure to water of about 71.6 degrees F, or in fatter men, 50 degree F. “In fatter men?” you say. Yes, fatter men require exposure to colder temperatures to get their furnace to kick on, because their body fat helps insulate their innards. Yup, innards. Keep in mind, these dudes were shivering lots at the coldest temperatures, some so much they asked to be removed from the water due to the discomfort.

There’s a nifty review of human cold exposure from 1994, put together by the US Army. (Young) The take-home message is that a variety of adaptations occur in those who are exposed to cold temperatures on a regular basis like fishermen, the Ama divers in Korea and aborigine tribes. These adaptations will likely give us more comfort and dexterity when exposed to cold by allowing warmer temperatures in extremities while at the same time conserving heat loss. Pretty cool stuff if you get a chance to read through it.


Cold Air – a refreshing change from all the hot air being blown around about CT

A recent study exposed men to cold air (19 degrees celcius/66 F) and put their legs on ice blocks intermittently. (Yoneshiro) After a two-hour exposure to these conditions, the BAT-positive group increased their metabolism by an average of 410 kcal/day. Sounds cool, right? Go ahead and write the headlines now: Hang out in the cold and burn 400 extra calories/day! The catch is this: the calories/day figures are extrapolated from 20 minutes of indirect calorimetry, so they didn’t actually burn 410 kcal/day. They may have if they had been exposed to the stimulus for 24 hours, but who wants to hang out in 66 degree weather in their underwear with their legs on ice blocks 4 out of every 5 minutes? Also, notice this is the “BAT-positive” group. The BAT-negative group experienced a metabolic rise of a whopping 42 kcal/day on average.

van Marken Lichtenbelt exposed fat and lean men to cold air (16 degrees Celsius) for 2 hours. Lean men’s metabolism raised from about 2020 kcal/day to 2300 kcal/day and fat men from 1950 to 2280 kcal/day from 22 degrees Celsius.

Wijers found variability between subject and a decreased physical activity when exposing lean and fat men to cold. Lean subjects total daily energy expenditure (TDEE) increased significantly by a mean 60 kcal by exposure to 60 degree temperatures. The cool thing about this study is that the subject lived in this environment for 48 hours in standardized clothing and sleeping conditions. Since subjects slept under a duvet, the daytime EE figures give us a better understanding of the response to the cold. The lean subjects EE increased by a mean 105 kcal/day. A reduction in activity seen in both the lean and obese groups complicates things, but gives us insight into a possible adaptive mechanism – decrease in activity making up for the increase in calorie burn for heat production = don’t starve and stay alive longer.

So you can see that exposure to cold air will raise the metabolism by varying degrees dependent upon your level of body fat, age, and temperature of the air.


Other neat stuff

Here is some neat stuff I came across which I find interesting but have no interest in investigating further at this time: melatonin regulates BAT activation in aminals (yup, aminals). Also, epinephrine is needed to activate BAT and to induce non-shivering thermogenesis in skeletal muscle. And then there’s cool stuff to read about type II deiodinase and cAMP and peripheral T4/T3 conversion in skeletal muscle.


So, do I take baths or what?

Above, I mentioned that I think Ray Cronise has the right approach for applying CT to aid in fat loss. The basics of his approach, if I’m not mistaken, are to just be cold. If you live in a place where it’s cold, don’t go to great lengths to warm yourself. Wear a t-shirt and shorts when you would normally wear jeans and a sweatshirt. Don’t use covers when you normally would to sleep. Occasionally expose yourself to freaky cold temperatures to give yourself a little metabolic boost. Does that not just make it all too simple?

It’s for this reason I think there just isn’t a whole lot to talk about. You don’t have to worry about water temperature, skin temperature, succumbing to hypothermic unconsciousness or optimizing the ratio of pre-bath ephedra to exposure time or whatever. Of course, this is half the fun for some – experimenting with all the variables gives them something to do and I dig it. If you’re entertained by self-experimentation and this puts some wind in your sails, have at it. If this is you, I urge two simple things: 1. Be safe 2. Design your experiment with some rigidity if you plan on reporting the results to others around the interwebz.

If you’re not into tons of self-experimentation and are just looking for a little extra fat loss benefit, just be cold. Cool? Cool. (pun intended)


AAAAAaaaaaaaan I’ve had about as much as I can handle

Jeff and I had lunch recently to discuss the state of SPEED and this website. We both expressed apathy toward many of the fat loss topics being discussed around the interwebz because of a huge lack of applicability to the end-user. This is one of them. While I don’t feel that CT is completely useless, I sense there is a very small percentage of the population willing to expose themselves to any amount that would actually garner a noticeable result. While I’m certainly not part of this percentage (1. I live in Phoenix – it’s never cold and 2. Putting my fork down works perfectly fine for me) I won’t discourage anyone from trying it or incorporating it, but this will most likely be the last I’ll investigate it.

Our approach to fat loss is based on the Bio-Psycho-Social model because we feel this is the best way to establish life-long habits, so I encourage you to employ the 80/20 rule to your fat loss efforts, recognizing that CT is most likely part of the 80 percent of activities that will only get you 20 percent of the result. Nail down some good dietary, sleep and exercise habits, take the time to foster a supportive social structure and positive mental environment, and then try stuff like cold baths or wearing stupid shoes or drinking unicorn piss to “speed up” your fat loss efforts.



Brite, R. (1986). Comparison of Weight Loss Effects of Starlite and Unicorn Urine: A Review. J Sphere Light, 2, 278-291.

Cannon, B. Y. P., & Keatinge, W. R. (1960). THE METABOLIC RATE AND HEAT LOSS OF FAT AND THIN MEN IN HEAT BALANCE IN COLD AND WARM WATER. Journal of Physiology, 154, 329–344.

Haman, F., Péronnet, F., Kenny, G. P., Massicotte, D., Lavoie, C., Scott, C., & Weber, J.-M. (2002). Effect of cold exposure on fuel utilization in humans: plasma glucose, muscle glycogen, and lipids. Journal of applied physiology (Bethesda, Md. : 1985), 93(1), 77–84. doi:10.1152/japplphysiol.00773.2001

van Marken Lichtenbelt, W. D., Vanhommerig, J. W., Smulders, N. M., Drossaerts, J. M. a F. L., Kemerink, G. J., Bouvy, N. D., Schrauwen, P., et al. (2009). Cold-activated brown adipose tissue in healthy men. The New England journal of medicine, 360(15), 1500–8. doi:10.1056/NEJMoa0808718

Wijers, S. L. J., Saris, W. H. M., & van Marken Lichtenbelt, W. D. (2010). Cold-induced adaptive thermogenesis in lean and obese. Obesity (Silver Spring, Md.), 18(6), 1092–9. doi:10.1038/oby.2010.74

Yoneshiro, T., Aita, S., Matsushita, M., Kameya, T., Nakada, K., Kawai, Y., & Saito, M. (2011). Brown adipose tissue, whole-body energy expenditure, and thermogenesis in healthy adult men. Obesity (Silver Spring, Md.), 19(1), 13–6. doi:10.1038/oby.2010.105

Young, A. J. (1994). Homeostatic Responses to Prolonged Cold Exposure: Human Cold Acclimatization. U.S. Army Research Institute of Environmental Medicine, 1.

Cold Thermogenesis: As much as I can handle
Tagged on: