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

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

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 that are associated with an increased risk of Alzheimer’s, including damage to blood vessels in the brain and the buildup of abnormal proteins, previous studies have found. The new research takes it a step further.

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

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

The thinning in that region of the brain could reflect a decrease in the number of brain cells, Morys said.

McGill researchers suspect that obese people, and possibly those who are overweight, a BMI from 25 to 25.9 — might be able to slow cognitive decline if they can get closer to a healthy weight.

Morys was unable to identify 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 pressurehigh 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 his colleagues analyzed brain scans from 341 Alzheimer’s patients and 341 obese people with a BMI of 30 or higher, along with scans from 682 healthy people.

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

Cognitive tests performed on the obese people in the study did not reveal obvious mental deficits, but the subtle changes in cognition related to weight loss seen in brain scans may not be detected in the types of tests used to assess mental status. . Morys said.

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

«The study showed that obese people and those with Alzheimer’s disease have common areas of the brain that are smaller in size, possibly due to a neurodegenerative process,» meaning that nerve cells in these regions may be suffering damage and they could be dying, Diano said.

The scans can’t show that obesity is causing thinning in these areas, but it makes sense that controlling body weight might be a way to reduce risks, he said.

«We know that if you take a mouse that has a genetic predisposition to Alzheimer’s disease and put it on a high-carbohydrate, high-fat diet—similar to a Western diet—you can induce increases in the animal’s body weight, and as it cognitive decline and brain degeneration is accelerated,» Diano said.

Could weight loss reverse the damage?

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

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

Although the obese individuals in the study did not show memory impairments, it is possible that what the researchers are looking at is an early stage in the development of Alzheimer’s, Malone suggested.

One limitation of the research is that it doesn’t directly report 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, one would think that it would have an impact on various organs, including the brain.»

While the hope is that weight loss can stop or slow brain degeneration, «unfortunately, we are finding more and more that there are certain points of no return,» Van Horn said.

«I think, based on examples like osteoporosis, that the chances of reversing the disease are less than the chances of preserving what’s there,» he said.