Two kinds of fat (also called adipose) cells exist: white and brown. Their function is to store fat for use by the body as energy but also to keep the body temperature constant and to cushion the organs of the body. Each white fat cell contains a droplet of fat (lipid). Each cell also contains, on its surface, receptors for glucagon and insulin, two hormones that play a key role in the regulation of the release of fat into the bloodstream for use by muscle cells for energy.
Brown fat cells are found primarily in newborns and are somewhat different, structurally containing many droplets of fat as well as many mitochondria. Their main function is to produce heat. They exist in small amounts in adults, but their role is very limited. Thus, the body needs a certain number of fat cells; however, too many are damaging to one’s health.
Recently, findings were published in the New England Journal of Medicine on the link between brown fat and healthy body weight. Researchers in Boston, Finland, and the Netherlands studied brown fat in adults, which is found mainly in the neck and around the collarbone (unlike white fat, which is found around the waistline and hips). The researchers found that lean people have much more brown fat than obese and overweight people, that women are more likely to have brown fat than men are, and that brown fat burns many more calories and produces far more heat, especially in cooler environments. Perhaps now a medication could be developed to stimulate fat cells to burn fat and produce heat and energy rather than just store the fat. Another approach could be to induce the body to produce more brown fat. Finally, another interesting finding is that it seems to be easier to lose weight by staying in a cool environment rather than a warm one.