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Women who hope to preserve their memory as they grow older may want to consider shedding some excess pounds.

That's because researchers at Northwestern University in Chicago have found a link between memory loss and weight gain in older women. Simply put, the more an older woman weighs, the worse her memory, according to the study published this week in the Journal of the American Geriatric Society.

The findings are based on 8,745 post-menopausal women, aged 65 to 79, who took a 100-point memory test. The score for normal memory is in the 90- to 100-point range. After completing the test, the score for each woman was matched to her Body Mass Index, or BMI.

It's a standardize measure based on weight and height.

The study revealed that for every one point increase in a woman's BMI, her memory score dropped by one point. "Any excess fat appears to be detrimental," said Diana Kerwin, the lead author of the study.

Previous research has shown that other conditions, including high blood pressure, elevated cholesterol levels and diabetes, can affect blood flow to the brain and impair cognitive function. These medical conditions often go along with being overweight. However, even when those conditions are not present, excess weight was still tied to reduced memory among the study participants. That suggests weight, by itself, is an independent risk factor for memory loss.

Furthermore, the researchers found that some types of fat - and where it's located - seem to be worse than others. For instance, "pear-shaped" women, who tend to pack the pounds on their hips and thighs, suffered more memory impairment than their "apple-shaped" counterparts who accumulate fat around their bellies.

Dr. Kerwin said admits she was surprised by this particular discovery because other studies have indicated that it's normally better to have a pear-shape than an apple-shape. When fat builds up around the abdomen - the traditional apple shape - it usually increases the risk of heart disease, type 2 diabetes and some cancers. "We have quite a lot to figure out," she said, referring to the unexpected findings related to pear and apple physiques.

Even so, Dr, Kerwin said researchers already have a few clues worth following. She noted that different types of fat release different cytokines and hormones that regulate a wide range of bodily functions. Abdominal fat, for instance, produces low levels of estrogen - which may minimize the overall negative effect of fat on older women whose ovaries are no longer producing a steady stream of the female hormone.

By studying these various substances and their specific effects on the body, researchers should gain a better understanding of how fat affects memory, said Dr. Kerwin. She added that she is already making plans to do this type of study.