为什么很多肥胖者减肥总是一而再、再而三地失败，即使减肥成功了一段时间，也往往会快速反弹？新发布的一项研究可能有助于解释这一现象。研究发现，肥胖可能会永久损害大脑在人体摄入脂肪和糖分后传递饱足感的能力。
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.
一项新研究发现，肥胖可能会损害大脑在人体摄入脂肪和糖分后传递饱足感的能力。
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，即使在肥胖患者减肥之后，大脑的这一改变可能仍会持续，这也许能解释为什么许多人在减肥后又胖回来。
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.
医学上定义的肥胖者身体质量指数超过30，而体重正常者的身体质量指数在18和25之间。
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日发表在《自然·代谢》期刊上的这项研究开展了临床对照测试，让30名肥胖患者和30名体重正常者摄入了糖类碳水化合物（葡萄糖）、脂肪（油脂）或水（作为对照）。每一组营养物在不同日期通过饲管直接输送到他们的胃里。
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.
在测试前一晚，60名研究参与者都在家中吃了同样的饭，直至次日早上使用饲管之前都不再进食。由于糖和脂肪都是通过饲管进入胃的，研究人员能够用功能性磁共振成像和单光子发射计算机断层扫描技术来捕捉大脑在30分钟内的反应。
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.
研究发现，体重正常者在糖或脂肪进入消化系统时大脑纹状体发出的信号会减慢，这证明大脑意识到身体已被喂食。
At the same time, levels of dopamine rose in those at normal weight, signaling that the reward centers of the brain were also activated.
与此同时，体重正常者的多巴胺水平会上升，这意味着大脑的奖励中心也被激活了。
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，当同样的营养物通过饲管进入肥胖患者的胃里时，大脑活动并没有变慢，多巴胺水平也没有上升。
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.
接下来，研究人员让肥胖者在三个月内减掉10%的体重，减重10%据悉能够改善血糖，重置新陈代谢，提升整体健康水平。
Tests were repeated as before — with surprising results. Losing weight did not reset the brain in people with obesity.
然后研究人员又重复了先前的测试，结果令人惊讶。减肥并没有重置肥胖者的大脑。
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对大脑产生了什么影响，这一影响是由脂肪组织本身还是摄入的食物种类，亦或是其他环境或遗传因素触发的，还有待更多研究。
