Much remains unknown about brown fat. Scientists are just starting to understand what brown fat does. If they can find out how white fat converts to brown fat, it could lead to a treatment for obesity .

Human newborns and hibernating mammals have high levels of brown fat. The other type of fat is white or yellow fat.

Brown adipose tissue, or brown fat, is one of two types of fat that humans and other mammals have. Its main function is to turn food into body heat. It is sometimes called “good” fat.

Share on Pinterest Fat cells can be white or brown.

White adipocytes, or white fat cells, have a single lipid droplet, but brown adipocytes contain many small lipid droplets, and a high number of iron-containing mitochondria. It is this high iron content that gives brown fat its dark red to tan color.

Brown fat has more capillaries than white fat, because of its higher oxygen consumption. Brown fat also has many unmyelinated nerves, providing sympathetic stimulation to the fat cells.

A lipid is another name for fat. Lipids are substances that dissolve in alcohol but not in water, such as fat. Oil and wax are also lipids. Lipids contain oxygen, hydrogen, and carbon. They have a lower oxygen content than carbohydrates.

The fat that builds up around a person’s waist and thighs is the white type. Brown fat mainly accumulates around the neck.

The functions of brown fat have only recently started to become clear. The main differences between the two appear to be as follows:

White adipose tissue (WAT), or white fat is the result of storing excess calories. When we consume too many calories, the body converts them into an energy reserve in the form of white fat.

WAT distribution affects metabolic risk. Large amounts of white fat around the abdominal area is associated with a higher risk of metabolic disease, while fat in the hips and thighs does not.

Brown adipose tissue (BAT) or brown fat generates heat by burning calories. When it is cold, brown fat’s lipid reserves are depleted, and its color gets darker.

Humans and mammals with higher levels of brown fat take longer to start shivering from the cold, than those with lower levels. Newborns do not shiver in the cold, because their brown adipose tissue levels are higher than in older humans.

Experiments have shown that adding more brown fat to mice has been found to increase the rate at which they burn energy, reduce the amount of fat on their bodies, and protect them from diet-induced obesity.

Newborns have a higher proportion of brown fat than adults, and this gradually drops with age.

Brown fat can be detected in adults using a positron-emission tomography (PET) scan. This is easier to detect when a person has been exposed to cold temperatures. Most brown fat can be found in the lower neck of an adult, and the area above the collarbone.

A person who is overweight has proportionally less brown fat than a person who is not overweight. Brown fat may play a key role in keeping people lean.