Want to Lower Your Dementia Risk? Watch Your Waistline

“But the risk is real,” says Shailaja Allani, director of the Center for Molecular Biology and Biotechnology at Florida Atlantic University. Allani studies cellular changes associated with dementia. The impact of obesity “shouldn’t get lost when looking at ways to prevent dementia.”

Excessive midsection fat — an apple-shaped body — and obesity in middle age, defined as a Body Mass Index (BMI) of 30 or higher, are strongly associated with an increased risk of dementia, says Rachel Whitmer, professor of neurology and co-director of the Alzheimer’s Disease Research Center at the University of California, Davis.

“Midlife central obesity is linked to future risk of stroke, type 2 diabetes, hypertension and cardiovascular disease, so these all play a role [in dementia risk],” Whitmer says. Whitmer has conducted several studies that examine the relationship between obesity and dementia. They suggest a strong association between midlife obesity — especially extra abdominal fat — and the risk of dementia.

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One study that followed more than 10,000 men and women over 27 years, published in BMJ in 2005, found that those who were obese at midlife had a 74 percent higher risk of dementia later in life, and those who were overweight (a BMI between 25 and 29.9) had a 35 percent higher risk than those of normal weight.

In another study, published in Neurology in 2008, Whitmer and colleagues measured midlife abdominal size in about 6,500 people ages 40 to 45 and then examined their medical records 36 years later. Those with the largest measurements had nearly three times the risk of dementia compared with those with the smallest measurements.

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Inflammation and “broken machinery” inside cells

Alzheimer’s and obesity “share some of the same broken machinery inside the cells,” Allani says. “Fat tissue is not just for storage. It also sends hormones that travel to the brain and trigger inflammation there. We know chronic low-grade inflammation is involved in many facets of Alzheimer’s disease,” she says.

Allani and a colleague reviewed 177 studies to see how such metabolic disturbances, including how the body uses insulin and how cells produce energy influence the development of dementia, in particular Alzheimer’s disease. Inflammation causes problems in the mitochondria — the cell’s energy-producing structures, which makes it hard for cells to produce the energy they need. It also contributes to the buildup of amyloid-beta plaques and tau tangles, and to brain cell death, all of which can lead to cognitive decline.

Problems in the mitochondria appear to be the most important. “Although the brain is only 2 percent of our body mass, it consumes about 20 percent of the energy derived from glucose metabolism,” she explains. When mitochondria don’t work properly, the energy supply throughout the body and brain is disrupted. That can contribute directly to brain cell damage and the development of Alzheimer’s disease.

Allani’s study focused on Alzheimer’s, but chronic low-grade inflammation is also linked to other kinds of dementias. It may have different effects, though. In vascular dementia, for example, inflammation mainly damages the lining of blood vessels.

Never too late to reduce risk

However, “it is never too late,” to do something about it, Whitmer says, adding that muscle strength seems to be protective, even among older people who are obese.

“Many studies point to muscle as being key in reducing [dementia] risk,” she says. “For elderly people who have a high BMI, focusing on exercise — both cardio and strength training — is essential.”

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Towers urges her patients to add weight training and to start a walking habit, which research suggests may also reduce dementia risk. She also recommends eating a plant-based diet.

She tells patients to try to walk every day, if possible — or at least five days a week — for 15 or 30 minutes at a time, and lift weights two or three times a week.

“Walking gets the heart rate up and the blood moving,” she says. “A prescription for walking should be the number one thing you get from your doctor. Weight training is important for overall metabolism and blood sugar control.”

MacDonald, who is a patient of Towers, walks on a trail with her daughter — “and my granddog” — once or twice a week and works out with resistance bands and 5-pound weights. She does wall push-ups and standing leg exercises in the kitchen while cooking. And she switched to plant-based eating. Today, 14 years after starting the new diet, her weight holds steady at 130 pounds.

She hasn’t been diagnosed with Alzheimer’s or any other dementia and wants to keep it that way. “Now that I know about the connection between weight and dementia, I would never go back,” she says.