Brown adipose tissue, or BAT, is most commonly referred to as brown fat. Unlike white fat, it creates heat to burn calories when activated. It is composed of various elements, including unmyelinated nerves, capillaries and mitochondria that contain especially high levels of iron. This is where the tissue gets its characteristic rusty, dark color. It generates body heat to create necessary warmth in temperatures that would otherwise cause shivering, which explains why it is so abundant in human infants and in hibernating animals like bears, lemurs and bats.
BAT reacts to cold conditions by burning calories and protects the body from the damage that can be caused by extreme cold. It keeps the body temperature of a newborn baby regulated because the immature central nervous system is not yet ready to do so. It allows hibernating animals to sleep for days, weeks and months on end without food for energy.
Though adult humans appear to lose the mitochondria that make up this fascinating tissue as they age, it still exists within the body, albeit in much smaller quantities. It still generates body heat and can actually be observed using specialized medical and laboratory equipment. Overweight individuals typically have the lowest amounts of this substance, instead carrying more of the white version in their abdomens and limbs. The precise reason as why this is the case is still unknown but research continues to pursue the answer. There could be a correlation between low brown fat levels and diabetes type 2.
There is research that has suggested that this type of tissue appears more in leaner individuals and can burn calories more effectively when stimulated with cold temperatures. Future studies intend to explore possible ways that this knowledge can be used as part of a treatment for obesity. Researchers believe that, if they can increase the amount of brown fat in an overweight individuals or alter their existing stores, they may be able to help people lose weight faster and more efficiently. There is still a significant amount of unknown information to discover in this field but the outlook is promising.