Until recently, nutrition scientists and the general public regarded all dietary fats as bad, and they made no distinction between the different types of fat tissue in our bodies. Once they researched a bit deeper, they found out that our bodies are prone to burning certain types of fat as opposed to storing them, certain fatty acids take on the role of hormonal precursors and other types take on all kinds of roles and provide various benefits that are yet to be examined and understood.
What are the different types of fat?
Nutrition scientists have found out that different types of fat stored in certain body areas play different roles in our bodies’ function. Additionally, they all have a different impact on our metabolism and overall health. The fitness rookie focuses on getting rid of the subcutaneous fat, which is the type that’s just beneath your skin and can be held together with the so-called “K pinch”.
This type of fat is made up of two separate layers, superficial and deep layer. The first layer that is just beneath your skin was the type of fat considered by nutrition scientists to be the first type to be used as a fuel source if food was not available. Those who overeat will experience the biggest increase in the superficial layer, while the people who are on calorie restriction will lose this layer.
If you had a poor diet and neglected physical activity, chances are that your body will start storing fat into other depots, like the deep subcutaneous layer. It’s been found that the deep layer serves multiple purposes. The first one being that it offers a protective layer from sudden environmental changes, softening minor collision impact against various sharp and solid objects. It is also crucial in controlling your temperature, having the role of an insulator against loss of body heat and the flow of warm or cool blood from and to the skin surface which can be drastically hotter or colder in comparison to your internal body temperature.
The deep layer also acts as an organ, by producing molecules similar to hormones, known as lipokines which control body inflammation levels, insulin resistance, and many others. It’s been found that the relation between the deep subcutaneous fat and insulin resistance and other illnesses is more pronounced in men than in women.
Inside our midsection, there exists another type of fat depot, which is often ignored, called visceral fat. This type has become the target of recent studies, since it’s been proven to be an especially strong indicator of development of type 2 diabetes, cardiovascular diseases, insulin resistance, metabolic syndrome and many other health issues. As we already said about the deep subcutaneous fat layer, visceral fat produces lipokines which affect our liver, and impact our body’s inflammation levels.
This type of fat has a serious role in controlling the balance of energy and maintaining a healthy weight. Scientists are eager to find any possible type of meds which would target these different types of fat depots and have a positive impact on our weight and overall health status. Taking into consideration the obesity epidemic that has taken control over America and our culture’s obsession with body image, it’s no wonder subcutaneous and visceral fat have become an integral part of our vocabulary.
What is Brown Fat ?
However, still have one more type of fat, that still hasn’t been mentioned on the news or “advertised”. This type is in a class of its own and is very different from the types we’ve mentioned so far. This mysterious type is known as “brown fat”.
The term itself makes it different from the type we hear a lot more often, which is “white fat”, comprised of visceral and subcutaneous fat. This type has long been believed to pose no issues in the human body since the only time people have it in any substantial amounts is while they’re babies. Brown fat is a lot more important in animals since it’s proven to be an essential surviving tissue in mammals that hibernate. The temperature in a mammal’s body is mostly generated by muscle action, which is generally the most active body tissue.
When the outside temperature goes down, the mammal’s body reacts by increasing the contraction of muscles, which mammals do voluntarily or by shivering. Muscle contraction is pretty inefficient from a metabolic perspective, with around 50% of the energy produced lost in the form of heat, instead of being used for moving an object (mechanical energy).
Trying to maintain or increase the body temperature is not an easy task. For example, this is one of the main reasons why people tend to lose weight while having a fever. The shivering which raises body temperature puts a much greater demand on our metabolism, which in turn dramatically increases calorie burning.
Mother nature has provided us with numerous examples of the conditions where mammals need to produce heat while being inactive. The most glaring example is hibernation. Animals like bats and some rodent species, which do hibernate, enter into a “deep sleep mode” which could last sometimes for months. You’ve surely heard of bears hibernating, but they aren’t thought of as real hibernators since they only slightly lower their body temperature which is near to their normal waking temperature and can be aroused very quickly.
This has left many researchers that were trying to sneak up on seemingly sleeping bears petrified. In a true hibernation, the body enters into an immobile state, very similar to a coma, where there’s almost no muscle contraction and the body temperature sometimes lowers to almost freezing levels. Bears, however, experience a decrease of around 12 degrees Fahrenheit; maintain their body temperature over the cool environmental conditions with the action of the tissue known as “brown fat”.
They only thing brown fat has in common with other types of fat is that it’s full of globules of deposited fat when fed, and nothing else. It owes its name because of the high amount of blood vessels in it and that it’s filled with mitochondria, making it much darker. Mitochondria are the cells’ “energy factories” which produce the majority of energy in the form of ATP, so that the cells can function properly.
The thing is that in brown fat, mitochondria are directed to produce heat instead of producing ATP, a process known as uncoupling. An analogy to this process would be when we’re holding down the clutch in a car with manual transmission. When you press or disengage the clutch, you uncouple the transmission from the car engine, and no power is directed to the wheels. In this case, if the clutch is pressed, the engine starts turning but doesn’t create any movement in the wheels. All the energy produces by the engine is lost in the form of hear.
Even if you press the gas, the engine will start turning faster but the car won’t move if the clutch is still uncoupled/disengaged. The energy coming from gasoline will be increased and more heat will be lost.
The mitochondria which are found in brown fat are similar to engines when the clutch is disengaged. In a normal state, body temperature is controlled by normal physical activity, leaving brown fat “quiet”. But, in hibernation, it has a lot bigger role in controlling body temperature, making the mitochondria a lot more active, the same as an engine that’s running at high revolutions per minute while the clutch is uncoupled/disengaged. The hibernating animals start burning more calories (analogous to gasoline), losing the energy in the form of heat. The heat produced spreads throughout the entire body via the bloodstream.
This brief overview of the basic physiology of mammals seems to offer almost no value to adult humans, since adults have very small amounts of brown fat, which is the main demographic group having weight maintenance problems. This doesn’t mean that benefits are non-existent, it just means that they’re limited. The brown fat that exists in adult humans is concentrated in specific small parts like the supraclavicular, mediastinal, cervical, paravertebral, suprarenal and para-aortic areas.
These specific areas are in the vicinity of big blood vessels, which is fairly logical since the brown fat remnants are likely to exist to control the core temperature in case the person is unable to move for a longer period of time or if he/she is exposed to cold outside temperature. Since the adult body assumes that it’s capable to produce a substantial amount of physical activity, it also assumes that there’s no need to preserve a tissue that demands a lot of energy and whose main and perhaps only function is to produce heat. This goes double in our modern age of air conditioners.
What are brown fat’s origins?
Current research has provided answers to the origins of brown fat, many of them looking quite surprising to the nutrition science community. Brown fat was first described by the Swiss naturalist Conrad Gessner. He described it as “neither flesh, nor fat”. Apparently he meant that that it didn’t appear to be either muscle or fat. When you look at brown fat under a microscope, you can see it has globules filled with fat, but it also has a big amount of mitochondria. It doesn’t contract and seemingly doesn’t release any type of hormone. Therefore, it was classified as an odd type of fat that didn’t have any type of function and was quickly forgotten about.
With the current advances in molecular biology, gene mapping and differentiation markers of the cells’ maturing process from undifferentiated stem cells to differentiated tissue cells, it is now possible to trace down the origins of brown fat all the way back to its precursors. What scientists discovered was nothing short of shocking. It was concluded that brown fat derives from a precursor cell found in skeletal muscles. We could say that brown fat is a very close relative to muscle and a distant relative to visceral and subcutaneous fat.
The details of the discovery are really extraordinary. In order to better understand how the scientists have come to this conclusion, one needs to get familiar with cell differentiation markers. Since the science behind this is very complex, we’ll try to explain in simple terms. All human beings develop from a single cell, which is a female egg cell fertilized by a spermatozoid, thus combining the genes of both the mother and father. As time passes and the cells start dividing further and further, they start specializing into becoming a specific type of tissue which has a specific function, thus forming all the different parts that comprise a human. They turn into different forms of tissue like liver tissue, blood cells, brain tissue, muscle tissue, kidney tissue, heart and many others. Even adult humans there’s a small “reservoir” of unspecialized cells that remain to replace the cells that were lost either to the aging process or because of an injury.
You can call these unformed and undifferentiated cells the “Neanderthals” of cell evolution. Their earliest form is called a stem cell and are mostly found in the embryo phase which have the potential to become any type of tissue cell. As these stem cells continue to evolve, they slowly start turning and making part of a specific tissue type.
In these early phases, skeletal muscle cells and white fat cells have a shared precursor cell. Due to the influence of androgens and some other compounds and factor, these shared precursor cells turn into either muscle cells or white fat cells. You can look at this precursor cell as a “common ancestor”. Following the Neanderthal analogy, this “common ancestor” cell evolves into an early-form muscle cell, called myoblast which further develops into a mature and fully grown muscle cell.
Scientists also found protein expression in brown fat that was only found in the muscle cells, not inside the white fat cells. It’s as if a group of chimpanzees were to suddenly come up to our doorstep for dinner just because we realized they weren’t distant cousins to us humans, but first cousins. Following the differentiation markers method, scientists were able to find the common ancestor from which muscle cell and brown fat cells diverged. They were also able to define specific signals which determine if this common ancestor cell will evolve into brown fat or skeletal muscle cell.
In addition to the great interest that these discoveries inspired in the scientific community, there’s also been talk of the benefits which the increasing of brown fat levels in adult humans can provide. As we already mentioned, adults have small amounts of brown fat, since it is the skeletal muscle tissue that is in charge of meeting the heat-producing requirements, which we already deemed brown fat’s “first cousin”.
If you want to produce heat and burn calories, all you need to do is simply move around, train or start shivering, but that would be incredibly stupid! The sad truth is that the majority of Americans aren’t exercising enough and in the so far unsuccessful pursuit of finding a quick solution to the obesity epidemic, scientists have started targeting brown fat as a potential tool for weight loss.
This seems as a logical conclusion, since if a pill can send a message to the body that would cause a 10-20% increase in the daily expenditure of energy, it would become equal to the benefit that exercising provides packed up in a small pill. However, it’s not that simple. First of all, brown fat is found in small amounts in adult humans, which is the main demographic that suffers from illnesses related to obesity. That’s why stimulating the brown fat directly would be a futile process because of its limited impact.
The key to getting benefit from brown fat is in increasing its total content to a substantial percentage of the total body weight and then stimulate it to increase the daily expenditure of energy, or the total number of calories that are burned throughout the day. But, there seem to be three big drawbacks that haven’t been fully taken into account.
The Skinny On Brown Fat
As we’ve thoroughly discussed already, brown fat and skeletal muscle cells have the same precursor cells. If brown fat is to be increased, the signals/messages for cell differentiation need to be switched from turning into muscle to turning into brown fat. When this happens and brown fat creation is increased, the pool from which skeletal muscle is created will become depleted, making the body ineffective in response to mechanical stress(exercise) or muscle injuries.
In the modern world, where low physical activity has been one of the main contributing factors to the obesity epidemic, this is one drawback which requires serious consideration. There exist several potential ways to do this, triggering the precursors to turn into brown fat, which would include something known as PRDM16 (identified transcriptional regulator), plus PPAR-gamma activators, garlic and olive oil.
We already concluded that the brown fat’s “waste product” when burning calories is heat. Your body will tolerate only a certain body temperature interval before entering a state of catabolism and experiencing tissue damage and overall fatigue. In extreme conditions, the brain can figuratively cook itself from too much heat causing the person to die from too high body temperature, a condition known as hyperthermia. Small children especially can suffer greatly from very high fevers with temperatures over 105ºF. If the temperature doesn’t go down, damage to the brain can occur and even death within hours, sometimes days.
Even a very persistent lower temperature fever has the potential to create problems with organ function, cognition and dehydration caused from the increased sweating. Certain individuals are especially sensitive to specific anesthetics and can enter a state called malignant hyperthermia when injected with anesthetics whilst preparing for surgery. This is a particular type of emergency and must be treated aggressively if it occurs. The drug DNP which has become famous among bodybuilders to decrease body fat, is believed to be the main cause of at least several death cases.
And even if scientists somehow found a way to force brown fat to release a measured amount of heat, it’s stimulated by drugs such as adrenalin. This type of drugs was used for many decades, since skeletal muscle will respond to the exact same meds by increasing the production of heat and numerous processes within the cells, a type known as thermogenic weight-loss meds. Unless scientists develop beta-adrenergic stimulants which would be applied to brown fat only, there is a potential risk for the development of many negative cardiovascular side effects or drastic mood swings and disturbances which were experienced with clenbuterol and products containing ephedrine. It’s truly extraordinary that brown fat tissue acts a lot like muscle tissue, even though it’s a cell which temporarily stores fat.
From an evolutionary and survival standpoint it is quite logical that a tissue that releases heat would be essential in times of prolonged hibernation and immobility. Taking into consideration the functions that brown fat and skeletal muscle share in relation to maintaining steady temperature levels, the discovery of their close relatedness is indeed very logical. For such a long time, it was considered that brown fat was just as any type of fat, which proves once again that things shouldn’t be taken at face value.
One of the many possible applications for this therapy involving the stimulation of brown fat could be for the treatment of comatose people or people who have experienced a stroke which left a body part paralyzed. However, for lifters and any type of athlete, even average people, trying to manipulate the amount of brown fat and its shared precursors with skeletal muscle, in order to increase caloric burning as well as decrease body fat, can ultimately cause various side effects.
We should thus put this discovery in the “extremely interesting” category, without thinking we’d draw too much of a practical value. It could be said that you could experience the same benefits if you stepped into a cool water bath, carefully lowering the water temperature until you start to shiver. Many bodybuilders claimed to have used this method to quickly drop fat before a bodybuilding contest, however, this could prove extremely harmful for those suffering from various heart illnesses, so if you intend on trying it, make sure you do it after making a thorough consultation with your doctor.