The brown fat has generated much interest among scientists for years. Little is known about it and there is less research on the brown fat than there is on the more common white fat. One thing is sure though – more brown fat in a body stands for a lower chance of developing diabetes and obesity. BAT might actually be an explanation for the mythical “faster metabolism rate” and the higher calorie burn rate that is characteristic of some people. Brown fat is desirable and unlike the yellow/white fat (white adipose fat, or WAT), it does not predispose people to metabolic diseases. Sounds like a dream come true? Keep on reading!
What is brown adipose fat?
BAT is metabolically active and it constantly releases a lot of energy to heat the nearby tissues. It is packed with mitochondria, which is how it gets its brown colour. The brown fat is located inside the body and surrounds the main organs (not to be mistaken for the bad visceral fat).It is very characteristic of newborns as it helps them maintain steady core temperature.
The brown fat is mainly located:
- in the intercoastal area,
- in the supraclavicular region,
- around the shoulder blades,
- along the entire spine,
- in the neck area,
- near the kidneys,
- near the adrenal glands.
Smaller (even one cell!) brown adipose tissue clusters are probably also located in various places where the white fat is located. A mix of brown fat and white fat is called “beige fat”.
Role of brown fat
The main role of brown fat is to maintain core temperature. BAT is metabolically active and it “heats” the areas where it is located by constant burning of fat in the mitochondria. Mitochondria can be compared to “furnaces” that burn fat and create heat. It is of key importance for the newborns which is why babies have the highest amount of brown fat. As we are ageing, the amount of brown fat in our bodies tends to get lower; however, it does not disappear altogether in every person.
An interesting fact: Brown fat is also present in all hibernating mammals. It is thanks to the brown fat that bears, for example, can “sleep” for a few months in the winter without having to eat!
Brown fat vs white fat – what’s the difference?
Brown adipose fat (BAT) and white adipose fat (WAT) are very different. And it is not only because of the colour.
- The main function of WAT is to store energy, whereas the main function of BAT is to generate heat.
- Brown fat is more venous.
- Brown fat is packed with larger and stronger mitochondria (organs for generating energy) than the white fat. This is how it gets its characteristic colour.
- Fat as triglycerides is stored in BAT in multiple bubbles; in case of the white fat (WAT), there is one larger bubble which gets larger as the amount of fat to be accumulated gets higher.
- Brown fat has an important protein: thermogenin (UCP-1) which stimulates the mitochondria to work.
- Brown fat is highly vascularised so it can absorb high amounts of oxygen and transport the energy to organs outside the fatty tissue. The subcutaneous white fat is not very vascularised.
Brown fat in adults
Not so long ago it was claimed that brown fat was characteristic of and specific only to newborns. It was thought that this fat completely disappeared by the time people reached adulthood. While scientific research on brown fat is still limited, more and more information on brown fat emerges.
Nowadays, having brown fat is highly desirable in adults. It is probably brown fat that strongly contributes to what we call “fast metabolism” in some people. Brown fat is also likely to prevent insulin resistance and obesity.
Measurement of brown fat
There is still little known about brown fat, mainly because the methods of brown fat measurement are limited. In the past, an autopsy of corpses was the only method to find out whether or not a given person had brown fat and to measure it. The tests of thermogenin expression marked some progress. Currently, modified PET tests are used to identify it; however, these still are not methods that can be used universally.
Unfortunately, “mortals” do not have access to reliable research on brown fat. You will not find out whether or not you have it if you get a body composition analysis.
Exposure to cold and brown fat
Scientists are already sure that many adults continue to have brown fat in their bodies. Research has proven that the amount of brown fat increases when you are exposed to cold. While examining the deceased, it was found that:
- People who are exposed to cold at work (Finnish construction workers working outside) have a developed brown fat, unlike office employees.
- The greatest amount of brown fat is found around the neck, or where the body tissue gets in touch with cold air.
- The BAT is more active in the winter. People who died in winter have more brown fat than those who died in August.
Brown fat might actually be responsible for the so-called body hardening when exposing it to cold. It is very likely that one of the major health benefits of ice swimming and cryotherapy is actually linked to the stimulation of brown fat.
How to increase the brown fat amount in your body?
If an effective, simple and long-term method for increasing the amount of brown fat were found, it could be a breakthrough in the treatment of insulin resistance, diabetes and obesity. There are real methods for increasing the amount of brown fat in body; however, many people are not satisfied with them. These methods include primarily: regular physical activity and low temperature that leads to shivering.
The brown fat creation is stimulated by a hormone discovered by Harvard scientists in 2012 and called irisin, also known as a “sport-hormone”. An attack of shivering due to cold which lasts between 10 to 15 minutes allows for the secretion of the same amount of irisin as the amount secreted by one hour of biking.
Researchers also found that in adequate conditions even white fat can turn into brown fat. It happens when the body is exposed to cold.
Does brown fat protect you from obesity?
One thing is clear – there is a correlation between the presence of brown fat in a body and obesity. Obese persons have less brown fat than people with the correct BMI. The question is whether the lesser amount of brown fat is the reason behind or rather the consequence of obesity?
It is also known that people who suffer from diabetes, insulin resistance and other glycemic issues have less BAT.
Scientists believe that simulation of brown fat creation, and in the future, maybe even brown fat transplants, may be a breakthrough in the fight with the obesity epidemic. They are taking intense efforts to learn the mechanisms behind BAT creation. Pharmacological means stimulating the BAT growth are currently undergoing clinical trials with humans. The results of the research with animals are very promising!
Ice swimming and brown fat
Even though ice swimming is universally believed to be healthy and beneficial to health, there is actually little hard evidence to prove it. Simulation of the creation of fat may be the answer to that issue and may help connect the dots between the health benefits of ice baths noticed by ice swimmers and the scientific approach to that topic. Following the rules of logic alone, ice swimming should stimulate the creation of brow fat. However, since it is difficult to measure the BAT content in the body, such research is very difficult.
Wrap-up:
Brown fat is one of the lesser researched and mysterious tissues. Unlike white fat, it does not contribute to the accumulation of fat around the body. Quite the opposite. Brown adipose fat (BAT) burns the fat and creates heat, thus maintaining the desired body temperature. If you have more brown fat, you can be less likely to develop insulin resistance, diabetes or obesity. You can stimulate the creation of brown fat in your body by physical activity and exposing your body to cool or cold temperatures.