Brown is the new white
Image credit: About.com
It is brown fat, actually, that we’re talking about here. Studies have shown that brown fat in your body burns fat like a furnace, though there isn’t much present in our bodies. A new study finds that one form of it, which is turned on when people get cold, sucks fat out of the rest of the body to fuel itself. Another new study finds that a second form of brown fat can be created from ordinary white fat by exercise.
Until about three years ago, researchers thought brown fat was something found in rodents, which cannot shiver and use heat-generating brown fat as an alternate way to keep warm. Human infants also have it, for the same reason. But researchers expected that adults, who shiver, had no need for it and did not have it. It was later reported that they had found brown fat in adults. They could see it in scans when subjects were kept in cold rooms, wearing light clothes like hospital gowns.
Researchers have found that brown fat in adults takes up glucose, but that does not necessarily mean it burns calories. However, a different group reports that brown fat can burn ordinary fat and that glucose is not a major source of fuel for these cells. When the cells run out of their own small repositories of fat, they suck fat out of the rest of the body.
But there is another type of brown fat, and researchers reported that, in mice at least, exercise can make it appear, by turning ordinary white fat brown. When mice exercise, their muscle cells release a newly discovered hormone that the researchers named irisin. Irisin, in turn, converts white fat cells into brown ones. Those brown fat cells burn extra calories.
It is suspected that humans, like mice, make brown fat from white fat when they exercise, because humans also have irisin in their blood. And human irisin is identical to mouse irisin.
In a study where men were chilled but not to the point of shivering (as that would have burned calories in itself), just a few ounces of these brown fat cells burned and average of about 250 calories over three hours.
Now, whether you would like to subject yourself to cold temperatures to help you lose fat, or tread on the tried-and-tested alternative of exercise, remember that this is not yet clinically proven to be an effective weight lose treatment.
Source: New York Times
