noun - Brown fat or Brown adipose tissue (BAT) are brown-colored cells that consume calories and generate heat while activated by the cold. It is a specialized tissue whose function is to produce heat. Its thermogenic capacity is such that it allows humans to live below thermoneutral conditions without having to rely on shivering muscles. BAT is highly vascularized and richly innervated by terminal fibers of the postganglionic neurons of the sympathetic nervous system.
BAT is filled with mitochondria that contain iron, giving the tissue a reddish brown color. BAT in adults are located in the upper back, on the side of the neck, in the dip between the collarbone and shoulder, and along the spine. Infants have it mostly as a sheet of cells covering their backs.
It is thought that thinner people have more BAT than heavier people; younger people have more than older people; people with lower glucose levels have more than those whose metabolisms are more sluggish; and women have more than men.