A hormone found in body fat could increase the risk of dementia and Alzheimer's disease in women.

The hormone is called adiponectin. Produced by fat cells, it actually helps regulate the metabolism and fend off diabetes. Low levels can lead to weight gain and changes in brain function.

Researchers at Tufts University say the new findings provide more evidence linking dementia to excess weight.

The researchers also found the hormone in men with dementia. However, there weren't enough men in the study to reach a clear conclusion.

The researchers say maintaining a moderate body weight throughout your whole life is the best protection. They also say more research is needed to understand what the findings mean for preventing and treating dementia.

"This study just reinforces our need for much more research on the relationship of insulin signaling to brain function and then its relationship to dementing illnesses such as Alzheimer's disease," Dr. Roger Brumback, a neurologist at the Creighton University School of Medicine in Omaha, Neb., told ABC News.

The study was published Jan. 2 in the Archives of Neurology.