There’s been a lot of buzz around brown fat over the past decade or so. But what is brown fat, and what makes it different from regular old body fat? Here’s a concise rundown.
White fat, or white adipose tissue, is the stuff comes to mind when most people think of body fat. Although it serves important functions, it builds up in undesirable areas like the stomach and thighs, and it can be tough to get rid of.
White fat’s primary purpose is to store energy. Put simply, when you consume more calories than your body needs, it typically stores those excess calories as white fat.
However, white fat isn’t the only type of fat in your body.
Brown fat is the body’s other primary type of fat—white fat’s arch nemesis. Their functions are actually quite opposite. Whereas white fat’s purpose is to store energy, brown fat’s is to release it.
More specifically, brown fat’s primary function is to heat the body when exposed to cold. And the mechanism by which it does this can actually be helpful for those trying to get rid of excess white fat.
Brown fat heats the body by burning white fat. These darker fat cells metabolize white cells, and instead of expending that energy for movement, such as when exercising, it’s released as heat.
It’s important to note that this heat generation is not the body’s first line of defense against cold. Shivering, the mechanism by which muscles in the body begin to move rapidly in an attempt to generate heat, will occur much earlier. Brown fat only kicks in when shivering isn’t effective enough, or when a person simply refuses to shiver through willpower.
Knowing all this, it makes sense that brown fat has been such a hot topic over the past few decades. Its existence brings up many interesting questions.
Can we lose weight by simply being cold? Can we manually activate brown fat to heat up at will?
First, a little more background on brown fat.
Where Brown Fat Builds Up
Although white fat is something we typically associate with poor diet, even infants are born with fat—both white and brown fat.
For infants, both white and brown fat play vitals roles in keeping the body warm. White fat acts as insulation, trapping heat all over the body as best it can. Brown fat, on the other hand, doesn’t cover the whole body.
In fact, in newborn babies, brown fat is usually only found in the shoulder blades and neck. Small pockets may be found elsewhere throughout the body, but these small regions are enough to generate heat for the whole body.
In adults, brown adipose tissue is still primarily found in the neck and shoulder blades. If an individual has brown fat anywhere else, it’s usually in sporadic patches throughout the back.
Building Brown Fat
If brown fat actually burns white fat for energy, that begs the question: can you build up brown fat for further fat-burning potential?
The Dutch extreme athlete-guru Wim Hof, often referred to as the “Iceman,” brought brown fat into the spotlight in the mid 2010s.
Wim Hof has demonstrated an incredible propensity for resisting cold temperatures. He has set world records for extreme feats of cold resistance, such as swimming under ice-blanketed lakes and standing completely submerged in ice cubes.
Even more impressive, Wim Hof has hiked Mount Kilimanjaro in only shorts and shoes—no shirt, jacket, or anything else. Most people would consider that kind of cold exposure lethal. So how does he do it?
Researchers have had this very same question, and Wim Hof has been happy to subject himself to their tests.
In a laboratory setting, the Iceman has demonstrated the ability to raise his core body temperature while submerged in ice. This was initially surprising because for any average Joe, sitting in a bucket of ice is a sure-fire way to lower internal body temperatures.
Although it isn’t the whole picture, some experts believe brown fat plays a vital role in this kind of cold resistance and heat generation. As we’ve discussed above, brown fat is able to metabolize white fat, turning that stored energy into heat.
When researchers were first delving into Wim Hof’s cold resistance abilities, there was a theory that he may have had more brown fat than most people, and was therefore able to generate more heat.
As luck would have it, Wim Hof has a twin brother who was also willing to subject himself to this kind of research. And the researchers found that although Wim Hof can withstand far greater extremes of cold exposure, he and his brother have virtually identical levels of brown fat. What gives?
Well, first of all, brown fat is clearly not the only factor when it comes to cold resistance. Anyone with enough mental fortitude can jump into a cold lake, regardless of how efficiently their brown fat can heat the body.
But brown fat and white fat aren’t alone. There’s another type that plays a role here.
Beige Fat: Something in Between
Beige fat is another type of fat that can be found throughout the body, although it a smaller scale. In fact, scientist typically don’t refer to beige fat as a collective mass, but rather refer to beige fat cells individually
Their secondary name gives you a hint as to what beige fat cells are: brown-to-white fat, or “brite” fat.
Beige fat cells are white fat cells that have transformed and have adopted some brown-like properties. There are some differences between beige cells and brown cells, but beige cells have the same ability to burn white fat to generate heat.
While brown fat is more “permanent,” in that it stays in place and doesn’t really change, beige fat cells can come and go throughout the body. Depending on different triggers, white fat cells can turn into beige fat cells, which eventually turn back into white fat cells. This leads to a variable dispersal of beige fat cells sprinkled throughout white fat.
Cold exposure is one such trigger. When subjected to cold temperatures frequently enough, the body will start to turn white fat cells into beige fat cells. These newly-formed beige fat cells can then cannibalize their nearby white cell neighbors in an attempt to generate heat.
Supplements with curcumin, a compound naturally found in turmeric root, have also been shown to increase beige fat cell production. And scientists are looking for even more ways to trigger this transformation.
Can Cold Exposure Burn Fat?
Due to the white-fat-burning capabilities of brown and beige fat cells, being adequately exposed to cold temperatures can indeed burn fat. However, there are a few caveats.
As noted above, the body will try to generate heat through shivering before brown and beige fat are activated. However, if someone resists the urge to shiver through willpower (which may be difficult, but is by no means impossible), they can increase the likelihood of brown and beige fat activation.
Of course, this means you have to be exposed to temperatures cold enough to initiate shivering in the first place. If you’re not cold enough for your body to start shivering, you’re probably not cold enough to activate these fat-burning fats.
Although this isn’t as telling as rigorous research, many people who have committed to some form of Him Hof’s cold exposure training have reported weight loss and visible fat loss. They aren’t immediate results, but many people have noted progress over several weeks or months.
And sure enough, scientific research backs up many of these claims.
Decades ago, early research seemed to indicate that cold exposure could boost fat loss. For example, a study in 1979 examined the effects of exercising in cold environments compared to room temperature environments.1Fat loss in the cold—a controlled study Fifteen obese men exercised for 2.5 hours each day for 1 week while wearing arctic gear in a room kept at -40 degrees Celsius (which also happens to be -40 degree Fahrenheit). After a week off, they did the same thing in a room at ambient temperature.
After exercising at room temperature, researchers found no significant change in fat or muscle mass. However, after the week of cold exercise, researchers noted a significant loss of body fat and increase in muscle mass. At the time, the fat loss was attributed primarily to the building of new muscle tissue, but we understand now that brown fat activation likely played a significant role.
Even more telling, another study from the 1970s similarly found that fat loss in cold environments exceeded expectations.2Loss of body weight and fat during exercise in a cold chamber In this study, ten men performed military exercise simulations in an arctic climate facility for one week.
At the end of the trial, the subjects’ fat loss far exceeded what would be expected from their 525 daily dietary calorie deficit. There was also a 3.25% average decrease in body weight, meaning that the fat loss did not directly correlate to new muscle mass. It is likely that some of this excess energy expenditure was due to brown fat activation for generating heat.
Following findings such as these, research in the past decade or two has focused more on the relationship between cold exposure and fat loss. Notably, some of this research has investigated the potential of brown fat activation as a means of fighting obesity.3Brown fat as a therapy for obesity and diabetes
Can Brown Fat Be Manually Activated?
As discussed in the previous section, brown and beige fat can be activated when someone is cold enough to shiver but resists the urge to do so. But is there a way to activate brown fat manually?
It would be very convenient to be able to generate body heat on command. And if you could manually active brown fats, you would also theoretically be able to burn fat on command.
Unfortunately, this is where things get a little less clear.
While research has shown that you can increase your potential for brown and beige fat activation by increasing cold exposure and taking curcumin supplements, there is little to no data about activating it on command.
Wim Hof claims he is able to activate his brown fat on command, and has indeed demonstrated something of the sort by raising his body temperature while submerged in ice. However, his particular methods aren’t well studied.
Per the Iceman himself, people can indeed learn how to activate their brown fat. He describes a process of focusing one’s energy at the base of the skull and feeling warmth generated in the shoulders and upper back, but his language is vague.
This doesn’t mean that it’s all a load of hogwash. Wim Hof actually has a record of not being able to quite accurately describe his methods, despite the methods themselves being very effective.
For example, part of Wim Hof’s cold training involves a meditative and energizing breathing technique. The technique consists of 20 to 30 deep breaths while lying down, then expelling all the air from your lungs and holding it without inhaling. When you feel the urge to breath, usually after 60 to 90 seconds, you take a deep breath and hold it for 10 seconds.
Here’s the discrepancy: While Him Hof describes the initial breathing as “charging the body’s cells with oxygen,” this isn’t biologically what’s happening. At rest, most people’s blood oxygen content is 98% or 99%. You may hit 100% with a few deep breaths, but you can’t “charge the cells with oxygen” beyond 100%.
In reality, the deep breathing technique expels carbon dioxide from the blood. Though you wouldn’t expect it, the urge to breathe is triggered by high levels of blood carbon dioxide, not low levels of blood oxygen. In fact, the body doesn’t directly sense blood oxygen content at all. High levels of carbon dioxide are a flag that tells the body to breathe.
So, when performing this breathing technique, a person can hold their breath for a long time not because of higher blood oxygen content, as Wim Hof describes, but because of decreased blood carbon dioxide content.
Despite inaccuracies like this, Wim Hof’s methods have still been thoroughly shown to be effective. And the Iceman isn’t alone in this purported ability to manually activate brown fat. Many adherents to his cold exposure training have similarly reported being able to manually activate brown fat. They usually use similarly vague language as well, with no concrete description of exactly how to perform it.
It may simply be that the best way to describe the process with our current knowledge is to “focus your energy at the base of the skull.” Hopefully, with future research, this particular facet of brown fat activation will be more thoroughly understood.
Brown fat and beige fat cells are incredibly fascinating and powerful components of our bodies. The ability to generate heat by burning unwanted white fat deposits almost seems like a superpower.
Research has identified a few triggers to building brown and beige fat, such as frequent cold exposure and taking curcumin supplements. Further research is ongoing, but this is a very promising tool in the field of weight loss.
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