想背单词？少吃肉！

In recent years, some research has suggested that a high-fat diet may be bad for the brain, at least in lab animals. Can exercise protect against such damage? That question may have particular relevance now, with the butter-and cream-laden holidays fast approaching. And it has prompted several new and important studies.

近年来，一些研究表明高脂饮食可能对大脑有害，至少动物实验的情况如此。那么，运动能否帮助我们抵抗这种损害呢？随着节日到来，一大波充斥着黄油和奶酪的食品正在袭来，这个问题有了特殊的重要性，由此也带来了一些新的重要实验。

The most captivating of these, presented last month at the annual meeting of the Society for Neuroscience in New Orleans, began with scientists at the University of Minnesota teaching a group of rats to scamper from one chamber to another when they heard a musical tone, an accepted measure of the animals' ability to learn and remember.For the next four months, half of the rats ate normal chow. The others happily consumed a much greasier diet, consisting of at least 40 percent fat. Total calories were the same in both diets.After four months, the animals repeated the memory test. Those on a normal diet performed about the same as they had before; their cognitive ability was the same. The high-fat eaters, though, did much worse.Then, half of the animals in each group were given access to running wheels. Their diets didn't change. So, some of the rats on the high-fat diet were now exercising. Some were not. Ditto for the animals eating the normal diet.

上个月，在新奥尔良神经科学学会(Society for Neuroscience in New Orleans)年会上，明尼苏达州大学(University of Minnesota)的科学家们提交了一个最为吸引人的发现：他们令一组大鼠听到音乐后从一个小室疾走到另一个小室，这是一个被普遍认可的测量动物学习和记忆能力的实验。接下来四个月，一半的老鼠正常饮食，另一半则愉快地享用更为油腻的饮食，其中包含至少40%的脂肪。两种饮食的总卡路里量是一样的。四个月后，动物们再次接受记忆测试。正常饮食的大鼠表现与之前一样；认知能力也一样。而高脂饮食组的表现就差得多了。接下来，两组各有一半大鼠被提供了滚轮装置。它们的饮食没有变化。这样，高脂饮食组的一半大鼠开始运动，另一半则没有运动。正常饮食组的大鼠也是同样的情况。

For the next seven weeks, the memory test was repeated weekly in all of the groups. During that time, the performance of the rats eating a high-fat diet continued to decline so long as they didn't exercise.But those animals that were running, even if they were eating lots of fat, showed notable improvements in their ability to think and remember.After seven weeks, the animals on the high-fat diet that exercised were scoring as well on the memory test as they had at the start of the experiment.Exercise, in other words, had "reversed the high-fat diet-induced cognitive decline," the study's authors concluded.That finding echoes those of another study presented last month at the Society for Neuroscience meeting. In it, researchers at Kyoto University in Japan gathered a group of mice bred to have a predisposition to developing a rodent version of Alzheimer's disease and its profound memory loss.

接下来的七周中，所有组别每周进行一次记忆测试。在这一阶段中，高脂饮食组的大鼠如果没有运动，表现继续下降。但是，那些在滚轮上跑步的大鼠虽然也摄入了大量脂肪，但思考和记忆能力有了明显的提升。七周后，高脂饮食的运动大鼠在记忆测试方面的评分已经恢复到了试验开始时的水平。研究作者得出了结论：运动“逆转高脂饮食带来的认知下降”。这一发现与另一项神经科学学会会议发表的研究互相呼应。在那项研究中，日本京都大学(Kyoto University)的研究人员喂食一组小鼠，使之易于患上啮齿动物的阿尔茨海默症和严重的记忆丧失。

Just why high-fat diets might affect the brain and how exercise undoes the damage is not yet clear. "Our research suggests that free fatty acids" from high-fat foods may actually infiltrate the brain, says Vijayakumar Mavanji, a research scientist at the Minnesota VA Medical Center at the University of Minnesota, who, with his colleagues Catherine M. Kotz, Dr. Charles J. Billington, and Dr. Chuan Feng Wang, conducted the rat study. The fatty acids may then jump-start a process that leads to cellular damage in portions of the brain that control memory and learning, he says.Exercise, on the other hand, seems to stimulate the production of specific biochemical substances in the brain that fight that process, he says.

为什么高脂饮食损伤大脑而运动又能防御这种损伤，原因还不清楚。美国明尼苏达大学附属明尼苏达VA医疗中心的研究员维查那格·马凡纳(Vijayakumar Mavanji)说，“我们的研究表明游离脂肪酸”是高脂饮食中实际渗透到大脑中的物质，脂肪酸可能启动反应，造成大脑记忆和学习区域的细胞损伤。他与同事凯瑟琳·M·科茨(Catherine M. Kotz)博士、查尔斯·J·比林顿(Charles J. Billington)博士和王传峰（Chuan Feng Wang，音译）博士进行了这项大鼠试验。马凡纳说，从另一方面来说，运动似乎能刺激大脑中特定生化物质的产生，对抗这一过程。

Of course, lab animals are not people, Dr. Mavanji cautions, and it's not known if exercise might protect our brains in the same manner as it does in mice and rats.Still, he says, there's enough accumulating evidence about the potential cognitive risks of high-fat foods and the countervailing benefits from physical activity to recommend that "people exercise moderately," he says, particularly during periods of repeated exposure to alluring, fatty holiday buffets.

当然，试验动物与人类不同。马凡纳博士提醒说，现在尚不清楚运动是否能像保护小鼠和大鼠一样保护我们的大脑。但他说，目前已经积累了足够证据，说明高脂饮食能带来潜在的认知风险，而锻炼运动能产生与之相抗衡的益处，因此他建议“人们适度运动”，在假期面对诱人的肥腻的自助餐时尤其需要如此。