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Obesity changes the brain, with ‘no sign of reversibility,’ expert says
肥胖或將永久損害大腦傳遞飽足感的能力
Obesity may damage the brain’s ability to recognize the sensation of fullness and be satisfied after eating fats and sugars, a new study found.
一項新研究發現，肥胖可能會損害大腦在人體攝入脂肪和糖分后傳遞飽足感的能力。
Further, those brain changes may last even after people considered medically obese lose a significant amount of weight — possibly explaining why many people often regain the pounds they lose.
而且，即使在肥胖患者減肥之后，大腦的這一改變可能仍會持續，這也許能解釋為什么許多人在減肥后又胖回來。
As defined medically, people with obesity have a body mass index, or BMI, of over 30, while normal weight is a BMI of between 18 and 25.
醫學上定義的肥胖者身體質量指數超過30，而體重正常者的身體質量指數在18和25之間。
The study, published Monday in Nature Metabolism, was a controlled clinical trial in which 30 people considered to be medically obese and 30 people of normal weight were fed sugar carbohydrates (glucose), fats (lipids) or water (as a control). Each group of nutrients were fed directly into the stomach via a feeding tube on separate days.
6月12日發表在《自然·代謝》期刊上的這項研究開展了臨床對照測試，讓30名肥胖患者和30名體重正常者攝入了糖類碳水化合物（葡萄糖）、脂肪（油脂）或水（作為對照）。每一組營養物在不同日期通過飼管直接輸送到他們的胃里。
The night before the testing, all 60 study participants had the same meal for dinner at home and did not eat again until the feeding tube was in place the next morning. As either sugars or fats entered the stomach via the tube, researchers used functional magnetic resonance imaging (fMRI) and single-photon emission computed tomography (SPECT) to capture the brain’s response over 30 minutes.
在測試前一晚，60名研究參與者都在家中吃了同樣的飯，直至次日早上使用飼管之前都不再進食。由于糖和脂肪都是通過飼管進入胃的，研究人員能夠用功能性磁共振成像和單光子發射計算機斷層掃描技術來捕捉大腦在30分鐘內的反應。
In people with normal weight, the study found brain signals in the striatum slowed when either sugars or fats were put into the digestive system — evidence that the brain recognized the body had been fed.
研究發現，體重正常者在糖或脂肪進入消化系統時大腦紋狀體發出的信號會減慢，這證明大腦意識到身體已被喂食。
At the same time, levels of dopamine rose in those at normal weight, signaling that the reward centers of the brain were also activated.
與此同時，體重正常者的多巴胺水平會上升，這意味著大腦的獎勵中心也被激活了。
However, when the same nutrients were given via feeding tube to people considered medically obese, brain activity did not slow, and dopamine levels did not rise.
然而，當同樣的營養物通過飼管進入肥胖患者的胃里時，大腦活動并沒有變慢，多巴胺水平也沒有上升。
Next, the study asked people with obesity to lose 10% of their body weight within three months — an amount of weight known to improve blood sugars, reset metabolism and boost overall health.
接下來，研究人員讓肥胖者在三個月內減掉10%的體重，減重10%據悉能夠改善血糖，重置新陳代謝，提升整體健康水平。
Tests were repeated as before — with surprising results. Losing weight did not reset the brain in people with obesity.
然后研究人員又重復了先前的測試，結果令人驚訝。減肥并沒有重置肥胖者的大腦。
Much more research is needed to fully understand what obesity does to the brain, and if that is triggered by the fat tissue itself, the types of food eaten, or other environmental and genetic factors.
要充分了解肥胖到底對大腦產生了什么影響，這一影響是由脂肪組織本身還是攝入的食物種類，亦或是其他環境或遺傳因素觸發的，還有待更多研究。
英文來源：美國有線電視新聞網
翻譯&編輯：丹妮
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