Scientists believe they have identified a 'good' fat tissue that helps burn calories and may lead to new treatments for obesity.

　　Reporting in three different studies in this week's edition of the New England Journal of Medicine, researchers from Europe and the U.S. say they have identified a fat known as brown adipose tissue in adults and discovered that it plays a role in how the body expends energy.

　　'At the very least, we have identified that there is an entirely new way of approaching the obesity problem,' said Aaron Cypess, an author of one of the studies and an endocrinologist at Joslin Diabetes Center in Boston.

　　The brown tissue was thought to be present primarily in young children and generally disappeared with age. Even when the brown fat was found in adults, it was believed to play no role in how the body stores and expends energy.

　　The advent of high-tech medical imaging, however, has given researchers a new glimpse into the human body that reveals that not only is brown fat present in adults, but that it also is metabolically active. The studies combined images taken with positron-emission tomography, or PET machines, with those from computed tomography, or CT machines, to identify the brown fat.

　　Brown tissue helps to regulate body temperature by generating heat. In contrast, white adipose tissue stores energy. Obese people have too much of the white tissue.

　　Francesco Celi, an endocrinologist at the National Institute of Diabetes and Digestive and Kidney Diseases, said the findings may lead to the development of drugs that either help the body produce more of the brown fat or activate existing brown tissue. Treatments likely would take years.

　　Obesity drugs have proved difficult to develop, and only a few have entered the marketplace. Most focus on curbing appetite or how food is absorbed in the body. Last fall, Merck & Co. scrapped development of its anti-obesity drug taranabant because of side effects.

　　The findings of Dutch researchers published in the NEJM raise the possibility of nondrug treatments related to brown fat, Dr. Celi said.

　　The researchers from Maastricht University found that brown tissue can be activated quickly by exposing people to colder temperatures. In their experiment, volunteers were tested after resting on their back for two hours in a room with a temperature of 61 degrees.

　　'Taken together, these studies point to a potential 'natural' intervention to stimulate energy expenditure: turn down the heat and burn calories,' Dr. Celi wrote in an editorial accompanying the studies. In an interview, he said there is still much research to be done and that the body may compensate for the increase in energy expenditure by triggering a desire to eat more to boost energy intake.

　　The studies also found that brown fat was more common in women, younger patients and patients who were thin.

　　Dr. Cypess and colleagues at Joslin are investigating the use of an artificial protein commonly used in spine surgery to stimulate brown tissue. The protein, known as bone morphogenetic protein, or BMP, is used to spur bone growth. Research suggests it also helps create brown fat.

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