How does your weight affect your brain?  It turns out quite a bit.  According to a new study, the fat cells in your body could be damaging your brain.  And the best way to protect it?  Exercise.

The study, which was published recently The Journal of Neuroscience, looked at how obesity and exercise affect the brain.  Researchers from Georgia Regents University evaluated mice that were bred to be obese and found that as they accumulated more fat cells, their blood showed larger levels of a substance called interleukin 1 which is linked to inflammation.  Scientists knew this already, but most thought that the brain was protected from this inflammation as there are no fat cells in the brain and it is generally protected from harmful substances by the blood-brain barrier.

But the study revealed that obesity can weaken this barrier, allowing interleukin 1 to seep on in.  In fact, researchers found the substance in several areas of the brain of the obese mice, in amounts that could significantly affect a person's ability to learn and remember. When researchers took a closer look at the obese mice's brains, they also found that their synapses were not functioning correctly, meaning that the sections the brain weren't talking to each other as smoothly as they should have been.  True to form, when the obese mice were tested on learning and memory skills, they failed miserably.  

But how could the researchers be sure that it was the fat that was causing the memory problems?

To test their theory, researchers next surgically removed the excess fat from each mouse.  As they expected, not only did the newly trimmed down mice not have interleukin 1 in their bloodstream, they also performed much better on their memory tests. 

The results were interesting, if not impractical.  After all, when extrapolating this at the human level, researchers realized that it's not possible for most obese humans to undergo surgery to remove all of their excess fat.  This would be unhealthy for so many reasons.  But in order to get a better idea of how these results could be understood more easily at the human level, the researchers gathered another group of obese mice and this time turned to exercise to see how it would affect the brain.

After 12 weeks of exercising, researchers found that the once obese mice still weighed the same as their sedentary peers, but they had lost significant amounts of fat.  More importantly, the mice that exercised did much better on their memory and learning tests than the obese mice who did not exercise.  Under a microscope, researchers could also see that the exercising mice had healthy synapses and showed no signs of inflammation in their brains.

Of course, it's important to note that these experiments were all done on mice. So it's not clear whether or not human brains would respond in the same way to fat and to exercise.  But researchers argue that for many people, it's worth prompting a discussion with your health care provider about the potential benefits of exercise- particularly if extra weight might be an issue. 

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