Belly Fat and Dementia: Is There a Connection?

Need one more bit of motivation to maintain a healthy weight? Research now suggests a connection between extra pounds around the middle and the risk of Alzheimer's disease.

A number of studies have suggested that excess body fat, particularly around the abdomen, may increase the risk of developing dementia, including Alzheimer's disease. Just how body fat and its many chemical components may affect the brain is a complex problem that researchers are now investigating, with support from the National Institute on Aging (NIA).

"We have two very serious public health burdens—Alzheimer's disease and obesity—and if they interact so that one accentuates the other, then this is obviously a significant crisis," says Dr. Suzana Petanceska, a program director in the NIA's Division of Neuroscience. "This is very important to know, because if metabolic abnormalities associated with obesity do indeed harm the brain, and we are able to understand how that happens, there is great potential for intervention."

At first, researchers did not consider obesity to be an independent risk factor for dementia, separate from the conditions obesity worsens, including diabetes and cardiovascular disease, which are both linked to dementia by numerous studies. But then, in the early 2000s, researchers turned their attention to obesity itself as an independent threat to the brain. Since then, imaging studies have demonstrated brain changes in association with obesity.

Location, Location, Location

There are several types of body fat (adipose tissue). Belly fat, also known as visceral fat, is the most damaging type. It wraps itself around organs, makes the abdomen protrude, and produces molecules that can pass into and interact with the brain. Excess visceral fat is risk factor for type 2 diabetes, insulin resistance, heart disease, stroke, and premature death, studies show. The fat that coats the hips and thighs, called subcutaneous fat, lies just below the skin and is benign in comparison.

In 2008, an NIA-funded study found that middle-aged people with large abdomens are more likely than are their flat-bellied contemporaries to develop Alzheimer's later in life. Study participants in the top third for belly size had a threefold greater risk of dementia than participants in the bottom third, even after researchers controlled for other factors, like diabetes, that increase a person's risk for developing Alzheimer's.

Belly fat churns out a host of hormones, including cortisol and glucocorticoids, known as stress hormones, which normally increase with age as well as during stress and are believed to affect cognition. "The more we understand about adipose tissue, the clearer it becomes that belly fat is its own disease-generating organism," says NIA's Dr. Lenore Launer.

As with other conditions that are affected by body fat, such as diabetes and heart disease, weight loss greatly lowers the risk. Researcher Dr. Rachel Whitmer points out that it also makes sense that maintaining a healthy weight would also reduce the risk of dementia. And another bit of good news: visceral fat comes off first when people lose weight.

Source: The Alzheimer's Disease Education and Referral Center (ADEAR). Visit the ADEAR website for coverage of the latest research on Alzheimer’s disease and other dementia.

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