White adipose tissue, or white fat, is used by the body to store energy in the form of triglycerides. This kind of fat has little mitochondria, hence its white color. Brown adipose tissue, or brown fat, is used to burn energy. Unlike white fat, it contains an abundance of mitochondria, which explains its brown color. Brown fat expends energy via non-shivering thermogenesis, and it is highly activated during cold conditions. Most people only have a small amount of brown fat in their bodies. Also, as they age, the levels of brown fat decrease. There are, however, individuals with higher amounts of brown fat than the normal population, which gives them an advantage in terms of burning calories, due to the increased thermogenesis and thus increase in metabolism.