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Obesity, Diabetes, and Alzheimer’s Disease: Is There a Link?

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The Gist

Recent research has dramatically altered how scientists view the link between Alzheimer’s disease, diabetes, diet, and obesity. 

To understand how these seemingly separate health issues are interconnected, it is essential to understand the process called “metabolism” that takes place in your body. Metabolism isn’t just how fast you digest food. It entails much more than that.

A key element to the process is insulin. Insulin is a hormone that aids the body in metabolizing fat and carbohydrates, including sugars. Your body converts carbohydrates into various forms of sugar in the body and those sugars are then used for energy.

In people with type 1 and type 2 diabetes, the body doesn’t produce enough insulin or becomes resistant to insulin—in other words, the body no longer responds to the insulin,  and thereby no longer metabolizes fats and carbs properly. This leads to a condition called hyperglycemia, or increased blood sugar, that can wreck havoc on the body’s organs and systems. 

It was commonly thought that the pancreas was the body’s sole supplier of insulin, but the new research indicates that insulin may be made in the brain.

A study from the Perelman School of Medicine at the University of Pennsylvania published in the Journal of Clinical Investigation found that insulin resistance—like that in diabetes—occurs in the brains of people with Alzheimer’s disease, a type of dementia that worsens over time.

The Pennsylvania research found that many people with type 2 diabetes have deposits of a particular protein—called amyloid beta—in their pancreases. That protein is similar to one that researchers found in the brain tissue of recently deceased Alzheimer’s patients..

This discovery is helping experts understand Alzheimer’s better than they have before. It’s being viewed now as a potentially metabolic disease, giving way to the term “type 3 diabetes.”

This isn’t a brand new discovery. As far back as 2005, researchers were suggesting that Alzheimer’s was a form of diabetes—that was the year when insulin-like growths were found in the brains of people who died of Alzheimer’s.

Another clue into the Alzeheimer’s-insulin connection is the use of synthetic insulin used in a nasal spray. Liraglutide is a diabetes drug that is currently being tested for its effectiveness in treating Alzheimer’s. The nasal spray is absorbed in the membranes of the nose instead of intravenously like typical insulin therapy for diabetes. Because of the delivery method, the brain better absorbs the insulin. 

Preliminary findings of the insulin nasal spray have prompted a complete study, which is currently underway.

People with diabetes are 50 percent more likely of developing Alzheimer’s disease, which leaves controlling risk factors for the disease even more detrimental to long-term health.

It’s been long known that a poor diet and lack of exercise can lead to obesity and increase your risk for type 2 diabetes, but recent research puts Alzheimer’s on the list of those risk factors. 

The Expert Take

Dr. Gerald Bernstein, director of the Friedman Diabetes Institute in New York City and former head of the American Diabetes Association, said the connection between  blood sugar and poor health is an obvious one, but to call Alzheimer’s “type 3 diabetes” is a “terrible misnomer.”

Dr. Bernstein said that the destructive proteins found in diabetic’s pancreases and those in Alzheimer’s brains, as well as the preliminary findings of the insulin spray therapy, offer insight into the condition, but it’s too early to be labeling it as another form of diabetes.

“Those are broad statements. They are far-fetched, but not too far-fetched,” he said. “It’s far from being a definitive thing, but it’s a reality.”

Further study into the subject is needed, but preliminary research shows promise, namely for people who have early-onset Alzheimer’s disease—the disease can strike people as young as 45 years old. With a better understanding of the condition and better pharmacological intervention means that Alzheimer’s could be as preventable as type 2 diabetes, Bernstein said.

The highlight of all of the recent research offers hope and insight into how Alzheimer’s develops and further clues into how blood glucose affects the body. Dr. Bernstein likened it to dipping your hand in honey: it’s going to contaminate everything it touches.

“Elevated blood sugars are a poison that sticks to everything,” he said. “The ultimate goal is to control blood sugars.”

The key, the doctor said, is that people with diabetes spend adequate time with diabetes experts to fully understand their condition, how to manage it, and to learn as much as possible about the disease.

The Takeaway

Managing blood glucose levels is an important health concern for anyone, even with or without any type of diabetes. Those already diagnosed with diabetes are strongly encouraged to manage their condition to prevent the numerous detrimental health effects it can have if left unchecked. 

Maintaining low blood sugar helps decrease the likelihood of developing type 2 diabetes and, according to recent research, possibly lowering your risk of Alzheimer’s and other forms of dementia.

Obesity is one risk factor for diabetes, although research has indicated that consumption of bad fats (saturated, trans, etc.) have no bearing on the risk of dementia.

The secret, as Dr. Bernstein said, is controlling blood glucose levels.

Ways to manage blood glucose levels include:

  • proper nutrition and a balanced diet
  • avoiding excess amounts of refined sugar or corn syrup commonly found in junk food
  • regular exercise
  • keeping a healthy weight
  • seeing a doctor regularly
  • properly managing diabetes

Other Research

- Brian Krans

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The Healthline Editorial team writes about the latest health news, policy, and research.

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