Be overweight in 40s 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 mirror some of those who have Alzheimers.
Scientists at McGill University in Montreal have analyzed the brain scans of more than 1,300 people in the first research to directly compare patterns of brain shrinkage in obese people and in patients with Alzheimer’s disease. Alzheimers.
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 increased risk of Alzheimer’s disease, including damage to blood vessels in the brain and the buildup of abnormal proteins, previous studies have shown. The new research goes even further.
“We have shown that there is a similarity between the brains of obese people and those with Alzheimer’s disease,” said the study’s first author, Filip Morys, postdoctoral researcher in neuroscience at McGill University. “And that 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.
Thinning in this 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 25 to 25.9 – may 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 unclear. 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 his colleagues examined brain scans of 341 Alzheimer’s disease patients and 341 obese people with a BMI of 30 or more, as well as scans of 682 healthy people.
All 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 taken by the obese people in the study did not reveal any obvious mental deficits, but it is possible that subtle changes in cognition related to weight loss seen on brain scans were not picked up by 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 brain areas that are smaller in size, possibly due to a neurodegenerative process,” meaning that nerve cells in these areas can suffer damage and die, Diano told me.
Scans can’t show that obesity causes these areas to thin, but it makes sense that controlling body weight could be a way to reduce risk, she said.
“We know that if you take a mouse that has a genetic predisposition to develop Alzheimer’s disease and put it on a high carbohydrate and high fat diet – similar to the Western diet – you can induce an increase in body weight in the animal and, as it gains weight with cognitive impairment and brain degeneration is accelerated,” Diano said.
Could weight loss reverse the damage?
The study opens the door to further exploration into whether weight loss could reverse some of the brain changes, said Dr. Joseph Malone, assistant professor of neurology in the University of Pittsburgh’s division of cognitive disorders. Malone did not participate in the study.
“We 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 rupture. brain blood vessels. and thus contribute to brain cell death,” Malone said.
Although the obese people in the study did not show memory decline, it’s possible what the researchers are seeing is an early stage in the development of Alzheimer’s disease, Malone suggested.
One of the limitations of the research is that it doesn’t directly report what people eat, just that they’re obese, said Linda Van Horn, chief of nutrition at Northwestern University Feinberg School of Medicine. , who did not participate in the study. .
“Given that, it leaves a lot of room for speculation and hypothesis generation,” Van Horn said. “Intuitively, one would think it would impact various organs, including the brain.”
While the hope is that weight loss may stop or reduce brain degeneration, “sadly, we are increasingly discovering that there are certain tipping points,” Van Horn said.
“I believe, based on examples like osteoporosisthat the chances of reversing the disease are less than those of preserving what exists,” she said.