Fat is good - as long as it is the calorie-burning brown fat variety. So understand your fat components before you rush off to shed you "good fat".
Brown fat burns off calories and generates heat in babies and small mammals.
Most of the body fat is white fat, which also provides insulation but stores calories. It becomes "bad" fat when an individual has too much. The "good" fat-brown fat-was considered essentially nonexistent in human adults.
The new study has found that adults have much more of this type of fat than previously believed.
"We now know that it is present and functional in adults," said the study's lead author, Dr Aaron Cypess, MMSc, of the Joslin Diabetes Centre in Boston.
"Three ounces of brown fat can burn several hundred calories a day," he added.
In the new study involving 1,970 study participants, researchers measured the patches of brown adipose tissue-brown fat-in people with the help of high-tech imaging method that combines positron emission tomography and computed tomography, called PET/CT.
By evaluating biopsy tissue of what appeared to be brown fat, the authors confirmed that they were, indeed, looking at stores of brown fat.
The researchers found that brown fat was located in an area extending from the front of the neck to the chest.
Of the subjects who had detectable brown fat, about 6 percent had 3 ounces or more of the fat.
"We believe that this percentage greatly underestimates the number of adults in the population who have a large amount of brown fat," said Cypess.
They also discovered that brown fat is most abundant in young women and least frequent in older, overweight men. In fact, women were more than twice as likely as men to have substantial amounts of brown fat.
"One theory for this is that women may have less muscle mass overall, so they need more brown fat to generate heat and keep warm," Cypess said.
The study appears in New England Journal of Medicine.