Adults with brown fat don't burn calories as believed

Adults with brown fat don't burn calories as believed
www.chinaview.cn 2009-04-09 11:10:05

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BEIJING, April 9 (Xinhuanet) -- It was generally believed, but could be worng, that humans lose brown fat after infancy, no longer needing it once the shivering response kicks in, said Thursday's issue of the New England Journal of Medicine.
Papers made by three groups of researchers indicate that nearly every adult has little blobs of brown fat that can burn huge numbers of calories when activated by the cold, as when sitting in a chilly room that is between 16 and 19 degrees centigrade.
Thinner people appear to have more brown fat than heavier people; younger people more than older people; people with lower glucose levels, presumably reflecting higher metabolic rates, have more than those whose metabolisms are more sluggish; and women have more than men. People taking beta blockers for high blood pressure or other medical indications have less active brown fat.
"The thing about brown fat is that it takes a very small amount to burn a lot of energy," said Dr. C. Ronald Kahn, head of the section on obesity and hormone action at the Joslin Diabetes Center in Boston.
The fat really is brown, researchers said, because it is filled with mitochondria, the tiny energy factories of cells. Mitochondria contain iron, giving the tissue a reddish brown color.
The hope is that scientists may find safe ways to turn on people's brown fat, allowing them to lose weight by burning more calories. But researchers caution that while mice lose weight if they activate brown fat, it is not clear that people would shed pounds -- they might unwittingly eat more, for example.
The data on global patterns of obesity are not good enough to say whether living in a cold climate makes people thinner.
(Agencies)
Editor: Wang Hongjiang