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The Truth About Brown Fat

Jan 31, 2012

You may have heard of the term "brown fat" before, so what does that mean exactly? It's not a type of fat you cook with, but rather a type of fat in your body. Brown fat, which is actually brown in color, is a term used to describe certain types of heat-generating, metabolically-active fat cells. Until recently, it was commonly thought that brown fat was only found in rodents and human infants. But more recent scientific research has discovered that brown fat is found in adults, too. The amount of brown fat people have varies greatly among individuals. Certain populations have more brown fat than others, with infants, slender people and younger women having the most brown fat. Brown fat is hardly ever found in obese individuals.

Brown Burns Fat

Brown fat has been called a calorie-incinerator, and for good reason. A new study found that a specific type of brown fat actually causes your body to burn other fat when you get cold. Your body becoming cold actually triggers this reaction and "turns on" the brown fat. Another recent study revealed that exercising causes brown fat to be created from regular white fat. Of course, this doesn't mean that you should make yourself cold on purpose in order to lose a few pounds.

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A new article published in the The Journal of Clinical Investigation confirms that brown fat does burn calories. Dr. Carpentier and his fellow researchers performed a specific type of scan that shows fat metabolism. This type of scan showed that brown fat can burn regular white fat and that glucose itself was not the major source of energy for brown fat cells. When these brown cells' own supply of fat ran out, they burned up the white fat cells for fuel. The lead researchers determined that the subjects' brown fat burned approximately 250 calories in a three-hour time period.

Another type of brown fat is found weaved in small amounts throughout your white fat, which makes it harder to identify on scans. A recent study on mice found that this type of brown fat actually originates from ordinary white fat. The mice in the study released a hormone called irisin when they exercise, and apparently irisin converts ordinary fat cells into brown fat cells, which then scorch calories. The study's researchers think that the same reaction takes place in humans when we exercise because the hormone irisin is found in our blood and it's exactly the same as the irisin discovered in mice.

The research on brown fat is still in its infancy, and it should be noted that although mice and humans have very similar DNA, we cannot always use results from mice studies to predict what may happen in humans. Further research is needed, but these results could be promising in the ever-evolving world of weight-loss.


Kari Hartel, RD, LD is a Registered Dietitian and freelance writer based out of St. Louis, MO. Kari is passionate about nutrition education and the prevention of chronic disease through a healthy diet and active lifestyle. Kari holds a Bachelor of Science in Dietetics from Southeast Missouri State University and is committed to helping people lead healthy lives. She completed a yearlong dietetic internship at OSF St. Francis Medical Center in Peoria, IL, where she worked with a multitude of clients and patients with complicated diagnoses. She planned, marketed, and implemented nutrition education programs and cooking demonstrations for the general public as well as for special populations, including patients with cancer, heart disease, diabetes, Alzheimer's disease, obesity, and school-aged children. Contact Kari at KariHartelRD@gmail.com.



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