Obesity May Increase Alzheimer’s Risk

by Sandra A. Swanson

September, 2009

Many obesity-related health risks, such as diabetes and heart disease, are well-documented. Research published online Aug. 6 in Human Brain Mapping could add Alzheimer’s disease to that list.

Investigators from UCLA and the University of Pittsburgh analyzed the magnetic resonance imaging scans of 94 adults in their 70s, all of whom are participants in the Cardiovascular Health Study, which tracks the health of adults over several years. Based on their body mass index (BMI), participants were classified in one of three groups: normal weight, overweight and obese.

The researchers specifically selected adults who retained good cognitive function for five years after the scans were taken. Paul Thompson, a UCLA neurology professor, says he and his colleagues wanted to show that the brain tissue loss wasn’t caused by a pre-existing neurological disease.

Researchers found that the overweight adults had experienced a 4 percent loss of brain tissue compared with normal-weight adults. Obese adults had experienced an 8 percent loss.

“The loss was particularly in the frontal lobe, the part of your brain that helps guide your behavior and planning,” says Thompson. “It was fairly drastic.”

Although the adults in the study were healthy, “the [cognitive health] risk is building up,” Thompson explains. “The guideline is, once you’ve lost about 10 percent of your brain tissue, you’ll notice it.”

Scans of early Alzheimer’s patients usually reveal brain tissue loss around 10 percent, he adds.

The next step is to pinpoint what causes the tissue loss. Says Thompson, “If you’re obese, the simplest explanation is just calories in versus calories out. But it may be the level of fat in the diet [that’s responsible]—you may be able to eat fantastic numbers of calories so long as they’re fruits and vegetables.”