Excerpts from: nytimes.com
Published: April 8, 2009
http://www.nytimes.com/2009/04/09/he...9fat.html?_r=1
"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, as when 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.
“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.
“Until very recently, we would have said that it is doubtful that differences in brown
fat really could contribute to obesity,” Dr. Nedergaard said. Now, he said he had changed his mind, at least for mice.
A second study, led by Wouter D. van Marken Lichtenbelt of Maastricht University in the Netherlands, involved 24 healthy young men. Ten were lean, the rest overweight or obese. The scans showed no brown
fat when the men had been in a room that was a comfortable temperature. But after they were in a chilly room for two hours,
scans showed brown fat in all but one, an obese man.
The studies, investigators say, should stimulate research on safe ways to activate brown
fat. It is known to be activated not only by cold but also by catecholamines, hormones that are part of the fight or flight response. That is why beta blockers, which block catecholamines, can suppress brown
fat activation.
Epinephrine, or adrenaline, and ephedra, an herbal supplement containing epinephrine, can stimulate brown
fat, said Dr. Rudolph Leibel, co-director of the Naomi Berrie Diabetes Center at the Columbia University Medical Center. But the
drugs have too many side effects to be used for
weight loss, he said, adding that while caffeine can bolster ephedra’s effects, it is easy to eat your way out of a brown
fat effect.
Brown
fat, Dr. Leibel said, “fits the fantasy — I eat what I want and burn it off.” That, however, is still a fantasy, he added."
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