U.S. researchers found no significant changes in memory or cognitive function among those over age 65 who were overweight or obese.
The study, published in the online edition of Neurology, found underweight participants had more cognitive decline over time.
"We do not know yet why being overweight or obese does not increase the risk for cognitive decline in old age, however being underweight may be a correlate of the initial stages of Alzheimer’s disease," study author Dr. Maureen T. Sturman, of Rush University Medical Center in Chicago, said in a statement.
"While past studies have found obesity in middle age increases a person’s risk for dementia or Alzheimer’s disease, our findings show obesity in old age has no effect on a person’s memory. These findings are consistent with previous studies showing that weight loss or low body mass index in old age may be a precursor of cognitive decline or Alzheimer’s disease."
The six-year study involved 3,885 people over age 65 in Chicago. Of the participants, nearly 25 percent were obese with a body mass index over 30, and 37 percent were overweight with a BMI between 25 and 29.9. Four cognitive tests were given at the beginning of the study and every three years thereafter over the six-year period.