Fat, Forty, and at Risk for Alzheimer’s?

May 5, 2005

May 5, 2005In one of the largest studies to date of excess weight and failing memory, researchers report that being fat in your forties may raise your risk of developing Alzheimer’s disease as you age. The research adds to a growing body of evidence that keeping weight down and following other heart-healthy measures is important for keeping the brain and body vital and alert in the senior years.

Doctors at the Kaiser Permanente Medical Foundation in California followed more than 10,000 men and women over a span of almost 30 years. They found that about 7 out of 100 men and women who were at a healthy weight during their forties developed Alzheimer’s or other forms of dementia by the time they were in their seventies. In contrast, about 8 out of 100 people who were overweight in their forties developed dementia in old age, and 9 out of 10 who were obese went on to develop the crippling mind disease.

Obesity, defined as a Body Mass Index of 30 or above, was a particularly serious risk factor for women. Obese women were twice as likely to develop dementia than women of healthy weight, while obese men were only slightly more likely to develop the disease.

Body Mass Index, or BMI, is a mathematical formula based on height and weight that doctors use to assess obesity.  A BMI of 18 to 25 is considered normal weight; 25 to 30 overweight; and 30 and above obese. A woman who is 5 feet 4 inches tall and weighs 170 pounds, for example, has a BMI of 29.

What the Study Showed

In the study, doctors reviewed detailed medical records of 10,276 Californians who belonged to the Kaiser medical plan during 1964 to 1973, then again up to 30 years later, in 1994. The men and women ranged in age from 40 to 45 years at the start of the period, and were in their seventies by the end, a time when Alzheimer’s disease becomes increasingly common.

The study participants were evaluated in terms of medical history and overall health, as well as demographic measures such as race. They were also assessed for obesity and overweight by calculating Body Mass Index as well as the “skinfold test,” or how much flesh could be pinched between the shoulder and the back of the upper arm.

Regardless of race or pre-existing medical conditions, being overweight or obese increased the risk of developing Alzheimer’s and other forms of dementia years later, the researchers concluded. The higher the BMI the greater the risk, especially among women. Men and women with excess skin-fold thickness were equally likely to be at increased risk of later Alzheimer’s, with a 60 to 70 percent greater likelihood of developing dementia.

The study confirms previous reports that excess weight is bad for the brain. A study last year of senior citizens found that those carrying extra pounds and with high blood pressure, high cholesterol, and poor blood sugar control were more likely to suffer from fading memory.

A Swedish study published in 2003 found that women who were overweight at age 70 were also much more likely to develop Alzheimer’s disease in their eighties.

The Perils of Excess Pounds

Carrying excess weight has been closely linked with diseases that affect the blood vessels, including diabetes, heart disease, and high blood pressure. There is growing evidence that such vascular ailments may be important risk factors for Alzheimer’s as well. In addition, obesity is often associated with disturbances in fat or sugar metabolism, such as high cholesterol and diabetes, which may affect the buildup of the sticky substance amyloid in the brain. Amyloid is thought to lie at the root of Alzheimer’s disease.

Scientists also speculate that fat cells may produce harmful chemicals that promote inflammation in blood vessels throughout the body, including in the brain. People who are overweight may also tend to have diets low in “good” fats, such as those found in fish.

Age remains the most important risk factor for Alzheimer’s: The older you are, the more likely you are to develop the disease. Smoking, high blood pressure, years of schooling, and genetic factors may also contribute to risk, other research has shown. More research is needed on the effects of body weight and other risk factors for Alzheimer’s disease.

Still, as the results of this and other studies suggest, keeping your weight down in your middle years and beyond may help you to remain mentally alert as well. With more and more Americans both young and old becoming obese, it is vital that people maintain healthy lifestyles to help maintain the brain. Learn more about Alzheimer’s at www.ALZinfo.org.

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


Rachel A Whitmer, Erica P Gunderson, Elizabeth Barrett-Connor, et al: “Obesity in middle age and future risk of dementia: a 27 year longitudinal population based study.” British Medical Journal, online edition, April 29, 2005.


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