Obesity is on a rampage. The World Health Organization pegs the number of those affected at more than 300 million worldwide, with a billion more overweight. With obesity comes an increased risk of cardiovascular disease, type 2 diabetes and hypertension.
Now there is more discouraging news.
In a study published in the current online edition of the journal Human Brain Mapping, senior author Paul Thompson, a UCLA professor of neurology, lead author Cyrus A. Raji, a medical student at the University of Pittsburgh School of Medicine, and their colleagues compared the brains of elderly people who were obese, overweight and of normal weight to see if they had differences in brain structure — that is, if their brains looked equally healthy.
They found that obese individuals had, on average, 8 percent less brain tissue than people of normal weight, while overweight people had 4 percent less tissue. According to Thompson, who is also a member of UCLA's Laboratory of Neuro Imaging, this is the first time anyone has established a link between being overweight and having what he describes as "severe brain degeneration."
"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," he said. "But you can greatly reduce your risk for Alzheimer's if you can eat healthily and keep your weight under control."
For the study, researchers used brain images from an earlier study called the Cardiovascular Health Cognition Study. Scans were selected of 94 elderly people in their 70s who were healthy — not cognitively impaired — five years after the scan was taken. To define the weight categories, they used the body mass index (BMI), the most widely used measurement for obesity. Normal-weight people were defined as having a BMI between 18.5 and 25; overweight people between 25 and 30, and obese people more than 30. The researchers then 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 the gray matter and white matter of the brain, 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, as well as 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, the 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," Thompson said.
"It seems that 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," said the University of Pittsburgh's Raji. "But that could mean exercising, eating right and keeping weight under control can maintain brain health with aging and potentially lower the risk for Alzheimer's and other dementias."
The research was funded by the National Institute on Aging, the National Institute of Biomedical Imaging and Bioengineering, the National Center for Research Resources, and the American Heart Association.
Other authors included April J. Ho, Neelroop N. Parikshak, Xue Hua, Alex D. Leow and Arthur W. Toga, all of UCLA; and James T. Becker, Oscar L. Lopez and Lewis H. Kuller, all of the University of Pittsburgh.
The UCLA Laboratory of Neuro Imaging, which seeks to improve understanding of the brain in health and disease, is a leader in the development of advanced computational algorithms and scientific approaches for the comprehensive and quantitative mapping of brain structure and function. The lab is part of the UCLA Department of Neurology, which encompasses more than a dozen research, clinical and teaching programs. The department ranks first among its peers nationwide in National Institutes of Health funding.