Video: Does belly fat cause dementia?

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msnbc.com contributor
updated 3/26/2008 4:05:30 PM ET 2008-03-26T20:05:30

People with a bulging waistline in mid-life could face a higher risk of dementia and Alzheimer’s in the senior years, a new study shows.

Previous research has shown that having an apple-shaped body increases the risk of diabetes, stroke and heart disease, but this is the first time it has been linked to dementia and Alzheimer’s.

In the study, which was published Wednesday by the journal Neurology, people who were both obese and had a large belly were three times more likely to be diagnosed with dementia in later years than those of normal weight and belly size. The risk of dementia nearly doubled in those who were a healthy weight but still had a bulging waist, suggesting that fat accumulated around the midline is particularly unhealthy for the brain.

“The take-home message from this study is that one should not only be concerned about their weight but where they carry their fat,” said Rachel Whitmer, the lead author of the study and a research scientist with Kaiser Permanente’s division of research in Oakland, Calif.

The findings are particularly concerning in light of the rise in obesity rates in the United States, Whitmer said. More than one-third of U.S. adults are obese and about half have abdominal obesity.

On the upside
“But the good news,” Whitmer added, “is that you can do something about it.” The type of fat that collects around the abdominal region is easy to accumulate but also easy to get rid of, she said. 

Lenore Launer, chief of the neuroepidemiology division at the National Institute of Aging, said it’s too early to conclude that abdominal fat is a direct cause of dementia.

“These findings are an indicator that something is happening in the brain and more research needs to be done looking at the role obesity is playing in brain health when people get older,” Launer said.

In the study, Whitmer’s team followed up on 6,583 men and women who had their waists measured between 1964 and 1973, when they were between 40 and 45 years old. The measurement used, known as sagittal abdominal diameter (SAD), is the height of the belly taken while a person is lying down and is considered a good indicator of abdominal fat.

A SAD of 9.8 inches or more is considered a large belly. Using medical records, the researchers found that between 1994 to 2006, when the study participants were between 73 and 87 years old, 1,049 had been diagnosed with dementia or Alzheimer’s disease.

Those who were both obese and had a large belly back in their 40s were 3.6 times more likely to be diagnosed later with dementia than those who’d had a healthy weight and belly size. Those who were a healthy weight but still had a large belly were 1.9 times more likely to develop dementia.

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The dementia risk remained even after the researchers controlled for diabetes, cardiovascular problems and overall obesity. Whitmer said this suggests that it’s the fat around the waist rather than general obesity that is causing most of the negative impact on the brain. One possibility is that this type of fat tissue, called visceral fat, secretes hormones and other chemicals, such as leptin, that could have a damaging effect on brain function.

The researchers in the study used special calipers to measure SAD, but people can get an idea if they are carrying too much fat around their belly by measuring their waist circumference.

A waist larger than 35 inches for women and 40 inches for men is generally a sign of too much belly fat, said Dr. Keith Bachman, an internal medicine physician and clinical lead of Kaiser Permanente's Care Management Institute Weight Management Initiative in Portland, Ore., who was not involved in the study.

Deflate that spare tire
For those with a big belly, the upside is that this fat tends to come off easier than other types. Abdominal fat is usually the first weight that comes off when we drop pounds and often exercise is enough to get rid of that spare tire.

Strategies for reducing belly fat are the same as shedding any excess weight. “Getting rid of it involves increased activity and eating less calories,” Bachman said.

Generally, reducing calories by 500 per day is sufficient to achieve moderate weight loss over time. Exercise is important, too, but it may take more than just going to the gym for those in mid-life. Bachman said it may help to find ways to be more active during the day, such as walking or biking to do errands and using stairs rather than the elevator.

Kathy Daly, a 43-year-old mother of three in Madera, Calif., can attest that exercise and cutting calories can shed the pounds and shrink the waist. Daly, who dropped 80 pounds and went from a pants size of 20 to a size 8 at the age of 40, was in part motivated by a family history that included two overweight aunts who developed dementia. 

“I just kind of assumed I would suffer the same fate as my aunts,” Daly said. “The idea that I could possibly prevent that is very exciting.”

Steve Mitchell is a science and medicine writer in Washington, D.C.  His articles have appeared in a variety of newspapers, magazines and Web sites, including UPI, Reuters Health, The Scientist and WebMD.

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