First there was research into kilojoule-burning "brown" fat, and now scientists say they've spotted a new type of "beige" fat in adults that might also prove useful in the fight against obesity. The study is published in the issue of the journal Cell.
"We've identified a third type of fat cell," Bruce Spiegelman, of Harvard Medical School, said. "There's white [and] brown, and now there is this third type that is present in most or all human beings."
It was once believed that only babies have brown fat, which helps keep them warm. Previous research suggested, however, that adults also have some brown fat. This study found that the brown fat found in adults isn't the same as brown fat in babies.
Brown fat in babies arises from muscle, but brown fat in adults is actually "beige" fat that occurs from the "browning" of white fat, the Harvard researchers explained.
How the study was done
In the study, Spiegelman's team cloned beige fat cells from mice and found that they lie genetically somewhere between white and brown fat. Normally, these beige fat cells are like white fat cells in that they have low levels of uncoupling protein 1 (UCP1), an important ingredient for burning energy and generating heat.
The beige fat cells, however, also have a "remarkable" ability to boost their UCP1 expression to the point that they can burn energy to the same degree as brown fat, the researchers said.
Spiegelman and his team also found that the energy-burning ability of beige fat cells is turned on by a hormone called irisin, which is released from muscle while exercising. It might be possible to treat overweight and obese people with irisin in order to boost the calorie-burning ability of their beige fat cells, Spiegelman speculated.
The skinny on brown fat
The U.S. Centers for Disease Control and Prevention offers advice about weight control.
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