How being obese may protect you from dementia – but only if you’re a certain age

Experts have long known that obesity in midlife is a major risk factor for developing dementia as you age.

But it’s intriguing that carrying a lot of excess weight later in life, when you’re over 65, has a protective effect against mind-altering brain diseases.

The two conflicting facts represent what researchers have called the “obesity paradox” – which challenges the conventional wisdom that obesity is always detrimental to health.

An important study published in JAMA Neurology examined 2,798 people, of whom 480 were diagnosed with dementia over a period of five and a half years.

Findings showed that while obesity in middle age was associated with a 40 percent increased risk of dementia, researchers found that at ages 60 to 65 it was associated with a lower risk.

The graph shows that obese people appear to have a survival advantage over normal or underweight people [courtesy of JAMA Neurology]

The underlying reason for the paradox is not clear.

Studies have repeatedly shown a link between obesity and a higher risk of dementia due to the inflammatory effects of a larger body size on the blood vessels that serve the brain. So an inverse relationship is counterintuitive.

Obesity in middle age is recognized as an important risk factor for vascular dementia, which is mainly characterized by reduced blood flow to the brain. Obesity puts you at risk for high blood pressure, which can damage blood vessels throughout the body.

It can also increase plaque in the arteries, causing blood to flow more slowly through the arteries.

One theory states that a protein produced by fat cells called adiponectin can do just that reduce inflammation in the brain.

Chronic inflammation is closely linked to a range of neurodegenerative disorders, including dementia and Parkinson’s disease.

However, Fat cells also produce proteins called cytokines, as well as hormones that send signals throughout the body that can trigger an excessive immune response.

Obesity rates have reached their highest level ever

Fighter cells are released as if the body is being attacked by a virus, causing the brain to become inflamed and increasing the risk of neurodegenerative diseases such as Alzheimer’s.

Obesity between the ages of 35 and 65 can increase the risk of dementia later in life by about 30 percent.

U.S. obesity rates are at an all-time high, with 42 percent of American adults qualifying as obese. Scientists have attributed this to unhealthy diets and sedentary behavior, fueled by the use of smartphones and social media.

A 2015 British study published in the prestigious journal Lancet followed two million people in their mid-fifties for about nine years, with about 45,500 people diagnosed with dementia.

The researchers found that people who were underweight and had a BMI of less than 20 kg/m2 had a 34 percent higher risk of dementia compared to people with a healthy weight.

However, those with a BMI in the obese category – 30 years and older – were associated with a 37 percent lower risk of dementia compared to the healthy weight group.

The above shows the prevalence of dementia – the percentage of people who have dementia – per year from 2000 to 2016. This shows a gradual decline in figures

Rates of obesity and progressive obesity have been on an upward trend since the turn of the century, peaking at 42 percent of Americans classified as obese

Even very obese people with a BMI over 40 had a 29 percent lower risk of dementia compared to people of a healthy weight.

This pattern held after 20 years of follow-ups and adjustments for other factors that might influence results.

The results confused scientists. However, some say one explanation may be due to the fact that obese people are more likely to visit the doctor for health problems that can contribute to dementia, such as high cholesterol and high blood pressure, and receive treatment for them.

Scientists have also highlighted that while obesity rates are steadily rising, dementia rates appear to have fallen. Although many fear an increasingly aging population could have the opposite effect.

Some warn that the idea of ​​obesity is a paradox could discourage doctors from discussing the risks of obesity to older patients.

Dr. Judith M. Kronschnabl, MA, a research center of the Munich Center for the Economics of Aging at the Max Planck Institute for Social Law and Social Policy in Germany, said: ‘It has been suggested that higher weight or weight gain in old age may be beneficial for maintaining cognitive performance [but] we find no evidence for this.

She added: ‘Accordingly, such a mistaken belief should not contribute to doctors’ reluctance in advising ‘obese or overweight patients to reduce excess body weight’.

Until middle age, people should aim for a BMI of 20 to 25.