Brown fat has a totally different purpose than white fat. It primarily serves to heat up a person’s body. In most mammals, including people, infants have larger stores of brown fat than adults. For humans, there is very little brown fat that remains after a person matures. Brown fatty tissue burns carbohydrates to create heat, and for this reason, it is fairly common for certain polar species to have a lot of it.
Animals in cold environments generally need more of this kind of fat because it helps keep them warm. Generally speaking, all baby mammals have a large layer of brown fat for the same reason. Baby mammals are smaller, so their bodies may have more trouble maintaining temperature and will generally lose heat faster. The brown fatty tissue helps compensate for this, and it can be triggered to produce more warmth as needed.
Some doctors are trying to harness brown fat as a weight-loss tool. People have small stores of brown fatty tissue in their necks that could potentially be activated. Many experts feel that this fat might be able to increase someone’s daily calorie (kilojoule) use and eventually cause weight loss. Scientists have been able to generate activity in brown fat to some extent by decreasing temperatures, but this may not necessarily prove to be a practical way of using it, partly because of discomfort.
When the body uses more calories after a workout or similar activity, people will often experience an increase in appetite. It is possible for a person to fight against his natural appetite, but this is often very difficult over the long term. Some experts worry that any successful attempt to activate the brown fat may be overcome by this natural balancing tendency, and this may negate the effectiveness of any future weight-loss therapy.
For a long time, it was generally thought that there was almost no brown fat remaining in a mature human’s body. This tissue shows up differently on x-ray tests than white fat, and this is how scientists discovered that people had some reserves that remained in their necks. The fat actually often looks like some kind of tumor in x-ray pictures. Scientists are still unsure of the actual purpose for the extra brown fat, although there is some evidence that it is still mainly used to generate warmth in emergency situations.
