Obesity isn't just bad for the body. Researchers now warn being overweight can be bad for the brain as well.

A study published in the latest issue of Neurology revealed that those who are obese showed a faster mental decline than those with a normal weigh.

The study surveyed more than 6,000 participants ranging in age from ages 35 and 55. Researchers in Europe analyzed their performance on memory and cognitive skills tests over a 10-year period.

The team found that test scores fell 23 percent faster for "unhealthy obese" participants who had high levels of fat, high blood pressure, high "bad" cholesterol, and high blood sugar.

"We do not yet know why obesity and metabolic abnormality are linked to poorer brain performance, but with obesity levels on the rise, it will be important to delve a little deeper into this association," Shirley Cramer, with the Alzheimer's Research UK, said.

Normal and overweight individuals who had two or more of the above metabolic risk factors also showed poorer cognitive function.