COSTA MESA, Calif. – Health experts say around half of American adults are overweight or obese. While excessive body weight is linked to a number of serious health conditions, including diabetes and heart disease, a new study reveals it can also reduce blood flow to the brain. Researchers warn this can put overweight individuals at great risk for Alzheimer’s disease.

The study examines brain blood flow in 17,721 adults between 18 and 94. To do this, researchers use a brain imaging technique known as single photon emission computed tomography (SPECT).

SPECT is a technique in which doctors inject a radioactive tracer into a patient’s blood and then use a special camera to look at the flow of blood. Participants were then split into five categories: underweight, normal weight, overweight, obese, and morbidly obese — to examine blood flow in each of their brains. The brain scan data reveals lower blood flow across virtually all brain regions as body weight increases.