26 August 2009

Obesity linked to stupidity, brain scans show

by Kate Melville

A person's risk of cardiovascular disease, type II diabetes and hypertension is known to be linked to obesity, and now researchers have established that being overweight can also affect a person's brain.

In the journal Human Brain Mapping, Paul Thompson, a UCLA professor of neurology, and colleagues compared the brains of people who were obese, overweight, and of normal weight, to see if they had differences in brain structure. They found that obese people had 8 percent less brain tissue than people with normal weight, while overweight people had 4 percent less tissue.

"That's a big loss of tissue and it depletes your cognitive reserves, putting you at much greater risk of Alzheimer's and other diseases that attack the brain," noted Thompson. "But you can greatly reduce your risk for Alzheimer's, if you can eat healthily and keep your weight under control."

The new study used brain images from an earlier study known as the Cardiovascular Health Study Cognition Study. The researchers converted the scans into detailed three-dimensional images using tensor-based morphometry, a neuroimaging method that offers high resolution mapping of anatomical differences in the brain.

In looking at both grey matter and white matter of the brain, the researchers found that the people defined as obese had lost brain tissue in the frontal and temporal lobes, areas of the brain critical for planning and memory, and in the anterior cingulate gyrus (attention and executive functions), hippocampus (long term memory) and basal ganglia (movement).

Overweight people showed brain loss in the basal ganglia, the corona radiata, white matter comprised of axons, and the parietal lobe (sensory lobe).

"The brains of obese people looked 16 years older than the brains of those who were lean, and in overweight people looked eight years older," said Thompson.

"Along with increased risk for health problems such as type 2 diabetes and heart disease, obesity is bad for your brain: we have linked it to shrinkage of brain areas that are also targeted by Alzheimer's," added co-researcher Cyrus A. Raji. "But that could mean exercising, eating right and keeping weight under control can maintain brain health with aging."

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Source: University of California - Los Angeles