A New Way to Lose Weight?

In the quest to fight obesity, scientists are looking at an intriguing question: Is it possible for adults to lose weight by having more baby fat?

Babies have lots of brown adipose tissue, or brown fat, so called because of its color. It is critical to the body's heat production. Unlike white fat cells, which store energy from the food we eat, brown fat consumes calories to generate heat. Revving up this process, research has shown, may help us grow leaner by burning more of the white fat.

Until recently, experts believed that only babies and children had brown fat, to help keep them warm before their young bodies develop techniques like shivering to help them cope with cold temperatures. A discovery last year that adults still have at least some brown fat has spawned hope among scientists and drug developers that the calorie-burning tissue may provide one solution to curbing obesity.

Researchers at Harvard Medical School have identified a protein in the body that appears to spur production of brown fat, including by converting some white fat cells into brown ones, and are now working to develop a drug that would encourage that process. They expect their work could lead to a new approach to treating obesity within a few years.

Other researchers are seeking ways to prompt the brown fat we already have to become more active, thereby prompting our bodies to generate more heat and consume more calories. One technique being investigated: exposing people to colder temperatures, which appears to trigger brown fat to turn up the body's heat.

"The obesity problem continues to be a real time bomb in the United States and in many other countries in the world," says Bruce Spiegelman, a professor of cell biology and medicine at Harvard's Dana-Farber Cancer Center in Boston. "We're not trying to replace diet and exercise, but frequently they're not enough or not effective."

Dr. Spiegelman and his team in 2007 discovered a protein called PRDM16 that appears to regulate the production of brown fat. Mice without PRDM16 don't form good, working brown fat cells, while those with PRDM16 do, studies showed. The researchers then genetically altered some mice so that they would produce greater amounts of PRDM16. The mice's heat generation and calorie-burning rate went up, too, according to research they published in the journal Nature in 2008...