New research paper offers another view of the correlation between obesity and dementia

From hypertension, to stroke, to heart disease, to cancer, too much fat in the diet is a scourge that continues to grow.

But a recent paper published by Dr. Anne Dorrance and her team in the Department of Pharmacology and Toxicology delves into a little-studied but significant issue with high-fat diets: consuming a high-fat diet or being overweight increases, your risk of developing dementia as you age.

“We know that in humans, being overweight or obese increases your risk of dementia development, and it seems the important timeframe for that is being obese as you go through middle age,” said Dr. Dorrance, who has studied the health effects of obesity for 20 years. “We’ve been using a rat model of obesity to understand how consuming a high-fat diet throughout your life increases your risk of dementia development and how it impacts the blood vessels in the brain.”

The Dorrance lab studies a specific form of dementia that occurs because the blood supply to the brain is disrupted or dysregulated. Specifically, the current research focused on the cerebral parenchymal arterioles (PAs), the tiny arteries that dive directly into the brain tissue and regulate blood flow.

In a two-year study that was interrupted for more than a year due to the COVID-19 shutdown, Dr. Dorrance and Jessica Yen, now a medical student at the University of Michigan, compared rats fed a high-fat diet to ones that received normal rat chow.

Their study used both male and female rats. Most studies in the literature suggest that females are protected from vascular injury, but this study suggests the picture is much more complicated.

“The structural changes we saw in the vasculature (the changes in the shape of the vessels in the brain) suggest females should develop dementia and males shouldn’t,” Dr. Dorrance said. “That’s the opposite of what the dogma suggests and also opposite to the data we got. Only the males showed any signs of cognitive dysfunction. Females had changes in the structure of their blood vessels but remained cognitively normal. The males had almost no change in vasculature, but they showed signs of dementia development.”

The research also showed that all the rats on a high-fat diet developed hypertension, but only female rats on that diet showed signs of the development of Type 2 Diabetes.

“That’s pretty interesting,” Dr. Dorrance said.

The research focused on the smaller blood vessels in the brain and offered some stark results.

“There is already quite a bit of literature looking at the effects of obesity in the cerebral vascular area, but those studies have been on much larger blood vessels. Studying smaller blood vessels allows you to link the vascular effects more closely to dementia development. The current studies highlight the need to consider males and females separately because their responses to high-fat feeding are quite different.”

While this study is over, Dr. Dorrance said there is still much work to do on the subject, and she hopes this paper will encourage others to investigate the effects of obesity on the brain.

Dr. Dorrance recognizes that it is hard to talk about the effects of being overweight or obese. “It’s a sensitive subject, but we also need to better define for people what being overweight does to your body. We are still learning, but it definitely shortens your health span, which is the number of years a person lives in good health.”