Insulin hitches obesity to memory

U. TEXAS-AUSTIN (US) — People who are obese display different brain responses than their normal-weight peers while completing a challenging cognitive task.

The results—which are most probably because of insulin sensitivity impairments—provide further evidence that a healthy lifestyle at midlife could lead to a higher quality of life later on, especially as new drugs and treatments allow people to live longer.

“The good thing about insulin sensitivity is that it’s very modifiable through diet and exercise,” says Mitzi Gonzales, psychology graduate student at University of Texas at Austin, who co-authored the paper with assistant professor Andreana Haley.

The study is published in the journal Obesity.

To better understand why midlife obesity is linked to higher risk of cognitive decline and dementia in old age, the researchers had middle-aged adults between 40 and 60 years of age complete a challenging cognitive task while undergoing functional magnetic resonance imaging.

While obese, overweight, and normal-weight participants performed equally well on the task, obese individuals displayed lower functional brain response in one brain region, the inferior parietal lobe.

Obese participants also had lower insulin sensitivity than their normal weight and overweight peers, meaning that their bodies break down glucose less efficiently.

Poor insulin sensitivity may ultimately lead to diabetes mellitus if the pancreas is unable to secrete enough insulin to compensate for reduced glucose use.

Impaired insulin sensitivity, which generally accompanies obesity, may serve as a mediator between midlife obesity and cognitive decline later on.

The researchers chose to examine insulin sensitivity because it helps regulate people’s metabolism and also affects cognitive functions.

The study is part of a stream of research in Haley’s lab that uses neuroimaging in middle-aged people to provide early identification of risk for cognitive decline later in life.

“Generally, very few people study the middle-aged segment of the population, but that’s when many chronic diseases are first identified and neurodegenerative processes are triggered,” Haley says.

“We found that while behavioral performance of obese middle-aged individuals may be the same—they can complete the same cognitive tasks as normal weight individuals—their brain is already doing something different to produce that outcome.”

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