A new study suggests that people who have large amounts of fat stored around their organs may have a higher risk of developing Alzheimer’s disease as they age.
This type of fat is not necessarily reflected in a high body mass index (BMI).
Visceral fat, which can accumulate around organs even in people with a healthy BMI, is associated with potential changes in the brain that occur decades before any symptoms of cognitive decline are observed, according to the study presented Monday at the annual meeting of the Radiological Society of North America.
Visceral fat has been associated with systemic inflammation (which occurs when the immune system is constantly activated, even when there is no health threat) and higher insulin levels, both of which are believed to be involved in the development of Alzheimer’s, according to Cyrus Raji, a neuroradiologist at Washington University School of Medicine in St. Louis and lead author of the study.
“We need to go beyond traditional conceptions of body fat, such as BMI, and look at the details of how fat is distributed to understand health risks,” Raji said.
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While an MRI of the abdomen is needed to confirm that visceral fat is present, a person may develop symptoms, Raji said.
According to the expert, symptoms that you may have accumulated fat around your organs include:
- A waist that is larger than the hips.
- Blood sugar levels that are high enough to diagnose diabetes or prediabetes.
According to the Alzheimer’s Association, more than 6 million people live with the disease in the United States. The group estimates that by 2050 that number will increase to 13 million.
To take a closer look at the potential impact of visceral fat on Alzheimer’s risk, Raji and his colleagues analyzed data from 54 cognitively healthy volunteers between the ages of 40 and 60 who had an average BMI of 32. A BMI of 30 or higher was consider obesity. according to the Centers for Disease Control and Prevention.
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The researchers measured a number of health parameters, including insulin and blood sugar levels. Using MRIs, they assessed the amount of fat just under the skin, as well as what surrounded the organs. MRIs were also used to measure the thickness of the cortex (the outer layer of the brain responsible for functions such as speech, perception, long-term memory and judgment) which becomes thinner as Alzheimer’s progresses.
Positron emission tomography (PET) scans were used in a subset of participants to determine whether two proteins associated with Alzheimer’s (tau and amyloid) were at higher levels.
When the researchers analyzed the fat measurements and brain scans together, they found that participants with more visceral fat had greater accumulations of amyloid in the brain, suggesting they might be at higher risk of developing Alzheimer’s disease.
Previous research has shown that inflammation and high levels of insulin, which can block proteins that break down amyloid in the brain, are linked to visceral fat, Raji said.
Because the earliest development of Alzheimer’s in the brain can begin up to 20 years before the first symptoms appear, researchers plan to study the potential long-term impact of visceral fat by following study participants.
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“That’s why we started with a middle-aged population,” Raji said. “We want to see how it could play a role in the development of Alzheimer’s, and that will give us an idea of the best period for effective interventions.”
The best way to lose visceral fat is through exercise, especially aerobic exercise, Raji said.
It’s not yet known whether getting rid of visceral fat can reverse its impact on the brain.
Dr. Mary Ellen Koran was not surprised by the findings.
“Since we already know that visceral fat is linked to so many health problems, including those affecting the heart, it makes sense that it would also be linked to poor brain health,” said Koran, an Alzheimer’s imaging specialist and assistant professor of radiology and biological sciences at Vanderbilt University School of Medicine. “But it’s important that we do studies like this to define that relationship.”
Although an obese person is more likely to have both types of fat, thin people can also have visceral fat without realizing it.
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Koran said he has seen “very thin people who don’t have a lot of subcutaneous fat but a lot of fat around their organs.”
However, Koran does not recommend that people who want to protect their brain get scanned for visceral fat until more research confirms the link.
