Nearly 30 million Americans suffer from diabetes, which makes them resistant to the effects of insulin, the hormone that transports glucose from the blood to inside body’s cells.

Glucose is the brain’s main energy source, and the disease is associated with an increased risk of strokes and dementia.

An MRI brain scan study of patients with Type 2 diabetes — in which patients produce insulin but their cells don’t use it efficiently enough — showed evidence of smaller brain size, particularly in regions that control memory and other cognitive skills.

Also, brain areas controlling planning skills were significantly thinner and showed more abnormalities when compared with those of nondiabetic controls.

The study volunteers with diabetes who were overweight displayed more brain abnormalities than those who had normal body weight.

All of the participants also underwent cognitive testing, and the scientists found that volunteers who suffered from diabetes scored lower on tests of memory and reaction time.