Obesity can shrink your brain...but so can too much exercise

How you take care of your body can have serious effects on the state of your mind...and either extreme might be bad for you. Two new studies reveal both obesity and strenuous exercise can be bad news for your brain.

The first study is the work of Antonio Convit at New York University. He performed MRI scans on the brains of 44 obese people and then 19 fit people of the same basic age and background. The obese subjects had more water in their amygdala, which among other things governs people's eating behavior. The orbitofrontal cortex was also consistently smaller in the obese people. This cortex is crucial for proper impulse control and for managing eating behavior.

These findings speak to the cognitive aspect of obesity and overeating, but it also could speak more broadly about how impulse control and other mental functions become diminished in obese persons. And, most worryingly, it appears that obese people's brains are literally shrinking, as Convit explains:


It could mean that there are less neurons, or that those neurons are shrunken.

So that's one extreme. But what about strenuous exercise? Women are known to experience specific health problems from too much exercise, because overly strenuous activity can reduce estrogen levels. Low levels of the chemical in premenopausal women has previously been linked with impaired mental function later on in life.

University of Toronto researcher Mary Tierney recently set out to connect these dots and see whether strenuous exercise itself is indeed linked with later cognitive impairment. She surveyed 90 healthy post-menopausal women to determine their lifelong exercise habits, and then she tested their current cognitive ability. There was a significant drop-off between the performance of those who had only exercised moderately versus those who had exercised strenuously. This suggests strenuous exercise really can have a negative cognitive effect, at least for women.

Now, both of these studies should be approached with some caution - obviously, 63 people in one study and 90 people in another doesn't necessarily confirm anything, and further study will be need to bear out or rule out the conclusions drawn from these studies. But both studies suggest there's some truth to the old truism that it's best to do things in moderation. If nothing else, your brain will thank you.

[Brain Research Press and Journal of Alzheimer's Disease, via New Scientist]