For more than 30 years, scientists have been intrigued by brown fat, a cell that acts like a furnace, consuming calories and generating heat, writes Gina Kolata in the New York Times.
Rodents, unable to shiver to keep warm, use brown fat instead. So do human infants, who also are unable to shiver their muscles to stay warm. But it was generally believed that humans lose brown fat after infancy, no longer needing it once the shivering response kicks in.
That belief, three groups of researchers report, is wrong.
Their papers, appearing Thursday in The New England Journal of Medicine, indicate that nearly every adult has little blobs of brown fat that can burn huge numbers of calories when activated by the cold, like sitting in a chilly room that is between 61 and 66 degrees.
Thinner people appeared to have more brown fat than heavier people, younger people more than older people; people with lower glucose levels, presumably reflecting higher metabolic rates, had more than those whose metabolisms were more sluggish, and women had more than men. People taking beta blockers for high blood pressure or other medical indications had less active brown fat.