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.

    科學(xué)家們相信他們發(fā)現(xiàn)了一種幫助燃燒卡路里的"有益"脂肪組織，可能會(huì)產(chǎn)生治療肥胖癥的新方法。

    據(jù)本周《新英格蘭醫(yī)學(xué)期刊》（New England Journal of Medicine）刊登的三項(xiàng)不同的研究顯示，來自歐洲和美國(guó)的研究人員表示，他們?cè)诔扇梭w內(nèi)發(fā)現(xiàn)了一種被稱為褐色脂肪組織的脂肪，對(duì)人體能量消耗有著重要作用。

    其中一份研究報(bào)告的作者、波士頓喬士林糖尿病中心（Joslin Diabetes Center）的內(nèi)分泌學(xué)家塞比斯（Aaron Cypess）說，我們至少發(fā)現(xiàn)了一種治療肥胖的全新方法。

    褐色組織此前被認(rèn)為主要存在于兒童體內(nèi)，通常會(huì)隨著年齡增長(zhǎng)而消失。即便在成人體內(nèi)發(fā)現(xiàn)褐色脂肪時(shí)，這種脂肪也被認(rèn)為和人體儲(chǔ)存與消耗能量沒有關(guān)系。

    不過，高科技醫(yī)療成像技術(shù)的出現(xiàn)讓研究人員對(duì)人體有了新的了解：他們不僅在成人體內(nèi)發(fā)現(xiàn)了褐色脂肪，而且還發(fā)現(xiàn)這種脂肪的新陳代謝很活躍。研究綜合使用了正電子發(fā)射斷層成象儀（PET）以及斷層掃描成象儀（CT）,以識(shí)別褐色脂肪。

    褐色組織通過生成熱量幫助調(diào)節(jié)體溫。相比之下，白色脂肪組織存儲(chǔ)能量。肥胖癥患者有過多的白色脂肪組織。

    美國(guó)糖尿病、消化及腎臟疾病研究所（National Institute of Diabetes and Digestive and Kidney Diseases）的內(nèi)分泌學(xué)家切利（Francesco Celi）說，這一發(fā)現(xiàn)可能有助于開發(fā)相關(guān)藥物，幫助人體生成更多褐色脂肪，或是激活現(xiàn)有的褐色組織。相關(guān)治療可能要耗時(shí)數(shù)年。

    事實(shí)已經(jīng)證明很難開發(fā)減肥藥，只有少量藥物進(jìn)入市場(chǎng)。大多數(shù)減肥藥都專注于控制食欲或是遏制人體對(duì)食物的吸收。去年秋天，默克公司（Merck）由于副作用的原因放棄了開發(fā)減肥藥taranabant.

    切利說，荷蘭研究人員在《新英格蘭醫(yī)學(xué)期刊》公布的這一發(fā)現(xiàn)帶來了從褐色脂肪著手進(jìn)行非藥物治療的可能性。

    荷蘭馬斯垂克大學(xué)（Maastricht University）的研究人員發(fā)現(xiàn)，人置身較低溫度下就可以迅速激活褐色脂肪。在實(shí)驗(yàn)中，自愿者在一個(gè)華氏61度（攝氏16度）的房間里躺了兩個(gè)小時(shí)后進(jìn)行測(cè)試。

    切利在研究報(bào)告的附加評(píng)論中寫道，綜合來看，這些研究都指向了一種可能的自然干預(yù)療法，即通過降低熱量和燃燒卡路里來刺激能量消耗。他在采訪中表示，目前仍有很多研究需要做，人體可能會(huì)通過提高食欲以增加能量攝入，來彌補(bǔ)能量消耗的增加。

    研究還發(fā)現(xiàn)，褐色脂肪在女性、年輕病人以及消瘦病人身上更為常見。

    喬士林糖尿病中心的塞比斯和同事正在研究一種人造蛋白質(zhì)的使用，這種蛋白質(zhì)常用于脊椎外科，用以刺激褐色組織。這種被稱為骨形成蛋白（BMP）的人造蛋白質(zhì)被用于刺激骨骼生長(zhǎng)。研究顯示，它也有助于生成褐色脂肪。