Wendy Wolfson
Newswire21.org

Obesity will not only raise your risk of heart attack, hypertension, diabetes and stroke. It may also shrink your brain.

In a sobering study, a team of researchers studied the brain scans of 94 cognitively and physically healthy elderly people. They found that obese people had about 8 percent less brain tissue in key regions than people of normal weight. People who are merely "overweight" had about 4 percent less.

The researchers suggested that losing enough brain tissue could raise the risk for - or hasten the onset of - dementia and neurodegeneration. But that's not all.

The obese people in the study had reduced tissue in their frontal and temporal lobes, which are associated with planning and memory; the anterior cingulate gyrus, which handles attention and executive functioning; the hippocampus, linked to long-term memory; and basal ganglia, governing movement.

The overweight subjects showed tissue atrophy in their basal ganglia, corona radiata, white matter made up of axons, and the parietal, or sensory lobe. 

The study was led by Paul Thompson, a professor of Neurology at UCLA, and Cyrus Raji, a student at the University of Pittsburgh School of Medicine. They and their colleagues used brain scans taken from the Cardiovascular Health-Cognition Study.

They followed their subjects over five years to rule out other factors that might cause brain degeneration. The researchers used the standard Body Mass Index to measure obesity. Normal people had a BMI between 18.5-25, the overweight between 25-30 and the obese topped 30. The researchers measured their blood insulin levels and tested them for diabetes as well as well as controlled for age, gender and race.

3D Images
Thompson converted the brain scans into 3D images using a technique called tensor-based morphometry to determine the differences in brain anatomy.

To be sure, the study was relatively small compared to an epidemiological study, which can cover tens of thousands of people. But Thompson noted the scans are a "very powerful tool" in understanding the inner workings of brains.

 "We just focused on healthy people," he said. "These are people who are elderly, cognitively normal, but are very different in their risk for Alzheimer's disease because of the things they do differently."

In their paper published in the current online edition of the "Journal of Human Brain Mapping," the researchers suggested that the correlation between obesity and brain volume may not be direct in the sense of one causing the other, but may be a result of factors relating to obesity such as hypertension, higher levels of certain hormones, lack of exercise, inflammation and impaired ability to get oxygen into the blood.

Keeping Your Wits
Thompson observed that symptoms of brain deterioration won't generally be evident until one has lost up to 10 percent of brain tissue.

"It is a cumulative burden not entirely under our control," he said. "You can certainly take steps to combat it. Exercise and diet are the two biggest factors if your brain stays healthy. The good news is that we can control these. You cannot do anything about getting old. By exercising and eating well you are 'putting money in the bank'. You are boosting your protection against brain disease."

 The study was funded by the National Institute on Aging, the National Institute on Biomedical Imaging, National Institute for Research Resources, and the American Heart Association.