Although fat often has a bad reputation it’s actually an essential substance in our bodies. However, excess body fat may cause weight gain and health problems. There are two kinds of body fat. The more common kind is the familiar white fat, which is an energy storage material. It contains fat molecules, which break down and release their energy if we don’t ingest enough calories for the body’s needs. The second, less common type of fat is brown fat. In brown fat, the fat molecules break down to generate heat. Researchers have noticed that mice and humans with more brown fat are leaner than those with less brown fat. Some scientists have suggested that brown fat could play an important role in controlling human weight.
Fat is also known as adipose tissue and contains cells called adipocytes. White fat, or white adipose tissue, is sometimes referred to as WAT. Brown fat, or brown adipose tissue, is also known as BAT. Each white fat adipocyte contains one large fat droplet, while a brown fat adipocyte contains several smaller fat droplets of different sizes. Brown fat also contains many more blood vessels than white fat.
For a long time it was thought that BAT existed only in rodents, animals that hibernate and newborn human babies, and that a baby soon loses its brown fat. Now investigators know that adult humans do have some brown fat, and recently it’s been discovered that some individuals have more extensive brown fat deposits than others. Brown fat has been found in the lower neck between the shoulder blades, on the sides of the neck, around the collar bones, and in the upper back and chest. Researchers say that obese people have less brown fat than people of normal weight.
Brown fat is light brown to red-brown in appearance. The cells of brown fat contains a much higher concentration of mitochondria than white fat cells do. The mitochondria contain iron and are responsible for the brown color of BAT. Mitochondria are cell organelles that usually make ATP (adenosine triphosphate) molecules, which are able to quickly break down to provide energy to the body when it needs it. Brown fat mitochondria, however, produce heat instead of ATP molecules. This process is known as “non-shivering thermogenesis”. It’s thought that babies lose brown fat as their muscles develop the ability to shiver, generating heat.
Scientists are investigating whether the brown fat content in adults can be safely increased and whether the brown fat can be safely activated once it’s present. Brown fat is naturally activated by hormones when an animal’s or a person’s body is cold. Researchers have been able to grow brown fat cells from precursor cells in the laboratory. They do warn us that if they find a way to increase the brown fat content in our bodies, and to trigger its activity, the brown fat will be a weight loss or weight maintenance aid rather than a miracle cure for obesity. A sensible diet and lifestyle will still be important for maintaining a healthy weight. If we eat more calories than our brown fat burns up, we’ll gain weight! However, having more brown fat might be a great help in a weight loss or weight maintenance struggle.