Being Overweight May Be Bad for Your Brain

July 13, 2020

Need more incentive to keep your weight down? A large new analysis confirms that carrying excess weight increases your risk of developing Alzheimer’s disease or other forms of dementia down the road.

Other studies have suggested that being overweight at midlife is tied to an increased risk of Alzheimer’s disease. The findings are important because obesity is a worldwide problem and experts project that by 2030, nearly half of American adults will be obese. Obesity is a major public health issue and is known to be a major contributor to heart attacks, strokes and diabetes. Obesity is also bad for the brain, these findings suggest.

For the study, British researchers analyzed health data of more than 6,500 men and women aged 50 and older. All were free of dementia and had no serious memory or thinking problems at the study’s start.

The participants were grouped according to weight: normal (a body mass index of 18 to 24.9), overweight (a BMI of 25 to 29.9) or obese (a BMI of 30 or greater). They also assessed whether they had abdominal obesity, or excess fat around the middle, defined as a waist size of over 40 for men or 34.6 for women.

The researchers followed them for up to 15 years. During that time, almost 7 percent developed Alzheimer’s disease or another form of dementia.

Compared to the men and women who had a healthy weight, those who were overweight were 27 percent more likely to develop dementia. Those who were obese were 31 percent more likely to develop dementia.

Being “apple shaped,” with fat around the middle, was particularly risky for women, the researchers found. Women with a waist size larger than 34.6 inches were 39 percent more likely to develop dementia than those with a healthy waist size. Men with a larger waist size also had a higher dementia risk but the increased risk was more modest. The findings were published in the International Journal of Epidemiology.

The study authors note that the study showed only an association and could not prove cause and effect, and that being overweight does not mean you will develop Alzheimer’s disease, only that you are at higher risk.

But excess weight is also tied to heart disease, being sedentary and other factors that are known to increase dementia risk. The researchers controlled for many risk factors, including whether individuals had diabetes, high blood pressure, or smoked, their age and sex, and genetic factors tied to Alzheimer’s disease, and still found an association between excess weight and increased dementia risk.

Earlier research has found that being obese at midlife is tied to an increased risk of Alzheimer’s disease. Excess fat has been tied to a greater accumulation of brain changes typical of dementia and reduced brain volume, an early marker of dementia.

“The ongoing obesity epidemic is predicted to cause a surge of dementia incidences in the near future,” the study authors caution. “Given the ongoing increase in obesity levels around the world, these findings have important implications in terms of designing appropriate interventions for preventing and managing contributing factors to obesity and associated consequences, including dementia onset.”

By ALZinfo.org, The Alzheimer’s Information Site. Reviewed by Marc Flajolet, Ph.D., Fisher Center for Alzheimer’s Research Foundation at The Rockefeller University.

Source: Yixuan Ma, Olesya Ajnakina, Andrew Steptoe, et al: “Higher Risk of Dementia in English Older Individuals Who Are Overweight or Obese.” International Journal of Epidemiology, June 23, 2020


Alzheimer's Articles