Obesity may cause brain changes similar to Alzheimer’s, research suggests

Being overweight in middle age has been linked to a greater risk of developing Alzheimer’s disease or dementia, and a new study shows that brain changes in obese people mirror those of some people with Alzheimer’s disease.

Scientists at McGill University in Montreal analyzed brain scans from more than 1,300 people in the first study to directly compare patterns of brain shrinkage in obese people and in patients with Alzheimer’s disease.

The scans revealed similar brain thinning in regions involved in learning, memory and judgment in both groups, according to the report published Tuesday in the Journal of Alzheimer’s Disease.

Obesity can cause changes in the body associated with an increased risk of Alzheimer’s disease, including damage to the brain’s blood vessels and the buildup of abnormal proteins, previous studies have found. The new research goes one step further.

“We showed that there is a similarity between the brains of obese people and people with Alzheimer’s disease,” said the study’s first author, Filip Morys, a postdoctoral neuroscience researcher at McGill University. “And it comes down to the thickness of the cerebral cortex.”

The cerebral cortex, which is responsible for higher brain functions such as speech, perception, long-term memory, and judgment in humans, is the outer layer of the brain.

Thinning in that brain region may reflect a decrease in the number of brain cells, Morys said.

The McGill researchers suspect that obese people, and possibly overweight people – a BMI of 25 to 25.9 – could slow cognitive decline if they could get closer to a healthy weight.

Morys could not set a target weight.

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Why is obesity dangerous for the brain?

The science is not clear. Other conditions that are bad for the brain — including high blood pressure, high cholesterol and type 2 diabetes — are also linked to obesity, Morys notes.

To take a closer look at the impact of obesity on brain structure, Morys and colleagues examined brain scans from 341 Alzheimer’s patients and 341 obese individuals with a BMI of 30 or more, along with scans from 682 healthy individuals.

All of the brain scans and other information came from two major health databases: the UK Biobank and the Alzheimer’s Disease Neuroimaging Initiative, a program that recruits participants across North America and is funded in part by the National Institutes of Health.

Cognitive tests performed by the obese subjects in the study revealed no obvious mental deficits, but it’s possible that subtle changes in cognition associated with the thinning of the brain scans are not picked up on the types of tests that are used to evaluate mental status, Morys said.

The new research “showed us something we didn’t know before,” says metabolism researcher Sabrina Diano, director of the Institute of Human Nutrition at Columbia Irving Medical Center.

“The study showed that obese individuals and people with Alzheimer’s disease have common areas of the brain that are smaller, possibly due to a neurodegenerative process,” meaning that the nerve cells in these regions can become damaged and die, Diano said.

The scans can’t show that obesity is the cause of these areas thinning, but it makes sense that controlling body weight could be a way to reduce the risks, she said.

“We know that if you take a mouse that is genetically predisposed to developing Alzheimer’s disease and you put that mouse on a diet rich in carbohydrates and fat – similar to the Western diet – you will experience an increase in body weight in the animal can cause and if they gain weight cognitive impairment and brain degeneration is accelerated,” Diano said.

Can Weight Loss Reverse the Damage?

The study opens the door to further research into whether weight loss could reverse some brain changes, said Dr. Joseph Malone, an assistant professor of neurology in the department of cognitive disorders at the University of Pittsburgh. Malone was not involved in the investigation.

“We do know that obesity is associated with other diseases that can affect blood vessels in the brain, such as type 2 diabetes, high blood pressure, high cholesterol and inflammation, all of which can lead to the breakdown of blood vessels in the brain. thus contributing to the death of brain cells,” said Malone.

While the obese individuals in the study did not show memory loss, it’s possible that what the researchers are seeing is an early stage in the development of Alzheimer’s disease, Malone suggested.

One limitation in the study is that it doesn’t report directly on what people eat, only that they are obese, said Linda Van Horn, chief of nutrition at Northwestern University Feinberg School of Medicine, who was not involved in the study. .

“Given that, it leaves a lot of room for speculation and hypothesis generation,” Van Horn said. “Intuitively, you would think it would have an impact on various organs, including the brain.”

While the hope is that weight loss can stop or reduce brain degeneration, “unfortunately, we are increasingly discovering that there are certain points of no return,” Van Horn said.

“I believe, based on examples like osteoporosis, that the chance of reversing the disease is less than the chance of keeping what’s there,” she said.

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