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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.
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 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 r 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
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.
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 those animals that were running
even if they were eating lots of fat
showed notable improvements in their ability to think and r 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 cise
in other words
had "reversed the high-fat diet-induced cognitive decline
" the study's authors 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，使之易于患上齧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 cise
on the other hand
seems to stimulate the production of specific biochemical substances in the brain that fight that process
he says.
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 l
he says
there's enough accumulating evidence about the potential cognitive risks of high-fat foods and the countervailing benefits from physical activity to remend that "people exercise moderately
" he says
particularly during periods of repeated exposure to alluring
fatty holiday buffets.