WAT vs. BAT - The Physiology of Body Fat

As odd as it sounds, many aren’t familiar with what body fat actually is. If you were to put someone on the spot, most just know it as the ‘jiggly’ layer of tissue under the skin that makes you look smooth and if you were to remove, resemble butter as if the fat you ingest in your diet magically floats and is deposited under the skin. First and foremost, fat is also referred to by the scientific name of adipose tissue. For a long time, adipose tissue was considered simply a storage organ, however, over the last decades there has been considerable accumulation of experimental data about the biology and biochemistry of adipose tissue1.

No longer considered to be an inert tissue that just stores fat, adipose tissue is a metabolically dynamic organ that is the primary site of storage for excess energy but it serves as an endocrine organ capable of synthesizing a number of biologically active compounds that regulate metabolic homeostasis. Adipose tissue serves a crucial function in the body as it a lipid storing and mobilizing tissue that consists of functionally specialized tissues able to produce heat and to produce or release a vast number of so called adipokines or adipocytokines2.

One thing to consider as well that doesn’t even cross the minds of many is that there is more than one type of adipose tissue. Technically speaking when it comes to mammals, there are two types of adipose tissue observed: White Adipose Tissue (WAT) and Brown Adipose Tissue (BAT). In a topical explanation, WAT is stored excess energy stored as triglycerides while BAT is metabolically active and dissipates stored energy as heat…meaning WAT stores energy and BAT releases energy. White is the commonly known, unsightly fat that we are aiming to get rid of when it comes to fat loss and is deposited under the skin, around the organs, etc. When the body goes into an energy deficit, the white adipose tissue can be used for energy and release fatty acids to be burned as energy for the liver and muscles3. Brown adipose tissue is responsible for thermogenesis, aka the production of heat. It contains more stable fatty acids that help keep the fatty acids inside the cells and is metabolically active4.

WAT (White Adipose Tissue)

Diving in a little deeper, WAT is composed of triglycerides primarily and these are stored as single, large droplets and surrounded by a thin ring comprising the cytoplasm and nucleus. It has traditionally been touted as strictly energy storage in which fatty acids are released for energy when required, however the research has shown that it is much more complex. WAT is located under the skin as subcutaneous fat and this is the majority of WAT in the body while there is also visceral WAT that surrounds inner organs. It is important to note that between the two WAT types, visceral WAT is correlated with poorer insulin sensitivity, Type II diabetes and other lifestyle related diseases5.

It has been shown that it is also needed for normal glucose homeostasis and inflammatory processes6. It has also been found that it has an endocrine function, primarily responsible for the secretion of leptin which is required for the maintenance of energy homeostasis and bodyweight7. Leptin deficiency or defects in the components of signaling pathways can lead to obesity as it controls energy balance and body weight primarily by signaling with the brain to alter food intake and control energy expenditure long term8.

BAT (Brown Adipose Tissue)

Regarding BAT, in mammals it is considered to have evolved as a specialized thermogenic organ that is responsible for non-shivering thermogenesis (NST)9. NST is originally defined as cold-induced increases in heat production not associated with muscle activity of shivering. Another stimulus to thermogenesis in brown adipose tissue is diet induced, activated by the ingestion of food. Brown adipose tissue has been shown in research to grow and regress in accordance to the extent to which it is stimulated, through both cold temperatures and diet and the capacity for both cold and diet induced non-shivering thermogenesis increases and decreases accordingly10.

Structurally, BAT is generally found inter-scapular, subscapular, axillary, paravertebral, mediastinal, periaortic areas and other regions including neck, intercostal vessels, mammary vessels, suprarenal and greater omentum11. Unlike white adipocytes, BAT adipocytes are smaller and contain multitudes of smaller lipid droplets and have far greater mitochondria and vasculature density. There is a large amount of mitochondria in their cytoplasm which express UCP1, a protein that stimulates in large part, non-shivering thermogenesis (NST)12.

Conversion of WAT to BAT

While we now understand that adipose tissue, both WAT and BAT have important roles in the human body, we can now shift our attention in the last part of this article to the conversion of WAT into BAT. It has been established in research that in response to appropriate stimuli and with certain dietary supplements in play, WAT can undergo a process known as browning where it takes on characteristics of BAT, mainly the noted induction of UCP expression and the presence of multilocular lipid droplets and multiple mitochondria found in BAT, making it more metabolically active.

It should also be noted though that it isn’t a direct conversion into ‘classic’ BAT but have their own classification. These ‘inducible’ or ‘recruitable’ brown adipocytes, also known as ‘BRITE’ (brown in white) or beige adipocytes, have low thermogenesis activity and a small number of mitochondria at basal state; however, once activated, they possess many biochemical and morphological features of BAT, such as the presence of multilocular lipid droplets and multiple mitochondria13. This conversion is beneficial as it can lead to better fat loss overall and furthermore aid in improving health markers such as improving glucose metabolism and lipid levels14,15.

WAT Conversion Via Supplementation

Now while there are several physiological adaptations that can spark the conversion of WAT into BAT or more specifically BRITE adipose tissue, there have recently been a few supplements that directly assist in this conversion as well. Two ingredients in particular have been shown to have prominent roles in this conversion process, being Aframomum melegueta (such as CaloriBurn GP?) and L-BAIBA (such as MitoBurn?), both from NNB Nutrition

MitoBurn? is a branded version of the ingredient L-BAIBA and is considered relatively new, emerging onto the scene as of late, but first gaining attention as early as 2014 in with a study showed that it has a direct effect on the upregulated PPARa so much that it caused WAT to be “beiged” giving it characteristics of brown fat, yet within the white fat cells16. It has also been shown to have a host of other very interesting and beneficial aspects including increase fatty acid oxidation overall17, improved insulin sensitivity18 and prevention of disuse-based bone and muscle loss19. There is also preliminary data suggesting L-BAIBA can also protect against fat gain in subjects with low leptin levels, an especially interesting benefit that goes long with the aforementioned role of leptin in body composition regulation20.

CaloriBurn GP? is a branded, high potency version of Aframomum melegueta, also known by Grains of Paradise or alligator pepper. This particular version is processed using ethanol and water through a natural extraction technology with HPLC & HPTLC standards. It preserves ALL the metabolism-enhancing bioactive compounds from human studies: 6-Paradol, 6-Gingerdione, 6-Shogaol, and 6-Gingerol. It has been used in traditional medicine for years and also as a spice in cooking and shares many similar bioactives as ginger, with two of the most intriguing for sports nutrition being 6-paradol and 6-gingerol21.

It has been shown in research that Aframomum melegueta significantly increases energy expenditure due to increase BAT activity when dosed at 40mg/day22. Another study found that in addition to increased energy expenditure, Aframomum melegueta also aided in decreasing visceral fat in lower abdomen specifically. Going beyond fat loss, a versatile potential benefit is that in both vivo and vitro studies, there is indication that the bioactive component 6-paradol can have a neuroprotective effect23. Lastly in animal studies and undergoing further studies in human subjects, there is also very promising data that it can help improve lipid profiles, attenuate hepatotoxicity and lower blood pressure for improved cardiovascular health24,25.

Conclusion: It’s a Matter of Black Brown & White

With the information provided in this article, the goal was to make your more familiar with what body fat actually is, the types found in the body and the physiology behind both WAT and BAT. There is so much emerging research coming out on the subject both in the physiology of the fat itself as well as ingredients in the sports nutrition space that can aid in converting WAT into BAT and the horizon of what is to come is indeed exciting. Here’s to a more intelligent future in the quest for lean physiques!

References

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