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When insulin resistance develops, the brain may have trouble using glucose efficiently. Some researchers have even used the phrase “Type 3 diabetes” to describe the connection between impaired brain metabolism and Alzheimer’s disease.

Is Alzheimer’s Disease Related to Insulin Resistance?

Is Alzheimer’s Disease Related to Insulin Resistance and Type 3 Diabetes?

Yes. Insulin resistance may play a major role in memory loss, Mild Cognitive Impairment (MCI), Alzheimer’s disease, and cognitive decline. In fact, some researchers have used the phrase “Type 3 diabetes” to describe the relationship between impaired brain metabolism and Alzheimer’s disease.

That phrase does not mean Alzheimer’s disease is literally diabetes. However, it does highlight something extremely important. The brain requires enormous amounts of energy, and insulin resistance can interfere with how well the brain uses that energy.

At the Carroll Institute in Sarasota, Florida, we believe one of the most important questions in cognitive medicine is: is this brain getting the energy it needs to function properly?

Why This Question Matters

For decades, Alzheimer’s disease was discussed mainly as an amyloid plaque problem. However, that model has failed to explain why removing amyloid does not restore lost memory or reverse cognitive decline.

Therefore, researchers have increasingly looked at other factors that may drive cognitive decline. One of the most important is insulin resistance.

Memory, focus, processing speed, and learning all require energy. When the brain struggles to produce or use energy efficiently, cognitive performance may decline. Consequently, blood sugar regulation and metabolic health deserve serious attention in patients with MCI, Alzheimer’s disease, and memory loss.

What Is Insulin Resistance?

Insulin is a hormone that helps move glucose from the bloodstream into cells. Once glucose enters the cell, the body can use it for energy.

Insulin resistance occurs when cells stop responding efficiently to insulin. As a result, the body may need more insulin to move glucose into cells. Over time, this can contribute to higher blood sugar, higher inflammation, weight gain, fatigue, and metabolic dysfunction.

Most people think insulin resistance matters only for diabetes. However, insulin resistance can affect the brain long before a person receives a diabetes diagnosis.

Why the Brain Needs So Much Energy

The brain is one of the most energy-demanding organs in the body. Although it represents only a small percentage of body weight, it uses a large amount of the body’s energy supply.

Your brain needs energy to:

  • Form memories
  • Process information
  • Maintain attention
  • Regulate mood
  • Support learning
  • Repair cells
  • Communicate between neurons
  • Maintain healthy brain networks

When energy production suffers, the brain often struggles. Therefore, metabolic health becomes a brain health issue.

Why Some Researchers Use the Term “Type 3 Diabetes”

The phrase “Type 3 diabetes” is not an official diagnosis. However, some researchers use it to describe Alzheimer’s disease because insulin signaling and glucose metabolism appear to play important roles in brain function.

When insulin resistance affects the brain, neurons may struggle to use glucose efficiently. As a result, the brain may experience an energy shortage even when glucose is available in the bloodstream.

This concept matters because it changes the conversation. Instead of asking only how to remove amyloid, we must ask why the brain is losing metabolic efficiency in the first place.

Insulin Resistance and Inflammation

Insulin resistance rarely occurs alone. It often travels with chronic inflammation.

As blood sugar regulation worsens, inflammatory signaling may increase. In turn, inflammation can further disrupt insulin signaling. This creates a damaging cycle.

For the brain, that cycle can be especially harmful. Inflammation may affect blood flow, mitochondrial function, immune regulation, and communication between brain cells. Consequently, insulin resistance can become one of several major forces driving cognitive decline.

Why Blood Sugar Matters Even Without Diabetes

Many patients assume blood sugar does not matter unless they have diabetes. That assumption can be dangerous.

A person may have insulin resistance, blood sugar swings, high fasting insulin, or metabolic dysfunction years before a diabetes diagnosis appears. During that time, the brain may already be affected.

Therefore, a normal blood sugar number does not always tell the full story. Precision Medicine often looks deeper by evaluating insulin, hemoglobin A1c, triglycerides, inflammation markers, body composition, lifestyle patterns, and other metabolic clues.

Why One Drug Cannot Fix Every Metabolic Problem

Alzheimer’s disease and MCI rarely come from one single cause. Dr. Dale Bredesen and other researchers have described many contributors that may drive cognitive decline in different patients.

One patient may have insulin resistance. Another may have sleep apnea. A third may have inflammation, hormone imbalance, mold exposure, vascular dysfunction, or toxin burden. Many patients have several contributors at once.

Consequently, the idea that one drug can address every unique combination of these variables does not make practical sense for many patients. Cognitive decline behaves more like a systems breakdown than a single drug deficiency.

What the EVANTHEA Precision Medicine Trial Supports

The EVANTHEA Precision Medicine Trial supports a systems-based approach to cognitive decline. Rather than focusing on one target, the study addressed multiple contributors at the same time.

Metabolic health was one of those contributors. In addition, the study addressed inflammation, sleep, nutrition, exercise, stress, hormones, and cognitive stimulation.

Participants demonstrated improvement in cognitive measures during the study period. That result matters because improvement is different from merely slowing decline.

For patients with insulin resistance, the implication is clear. If the brain has an energy problem, then improving metabolic health may become a critical part of supporting cognitive performance.

Insulin Resistance and Neuroplasticity

Neuroplasticity is the brain’s ability to adapt, reorganize, and strengthen neural pathways. At the Carroll Institute, we often describe neuroplasticity as a turbocharger for Precision Medicine.

However, neuroplasticity requires energy. If the brain struggles with insulin resistance, inflammation, or poor mitochondrial function, it may not respond as well to rehabilitation.

Therefore, metabolic repair and brain rehabilitation should work together. Precision Medicine helps identify why the brain lacks energy. Functional Neurology helps stimulate the networks that need support.

The Carroll Cognitive Method™ Perspective

At the Carroll Institute, we do not simply ask whether a patient has Alzheimer’s disease, MCI, or memory loss. We ask a deeper question:

Why is this brain struggling?

For many patients, insulin resistance and metabolic dysfunction may be major contributors.

The Carroll Cognitive Method™ combines:

  • Precision Medicine to identify metabolic and biological contributors
  • Functional Medicine to address root causes such as insulin resistance and inflammation
  • Functional Neurology to evaluate and rehabilitate affected brain networks

This approach allows us to move beyond labels and focus on the systems that influence brain performance.

Hope Without False Promises

Is Alzheimer’s disease related to insulin resistance and Type 3 diabetes?

For many patients, the answer appears to be yes.

That should not create fear. Instead, it should create opportunity. Unlike age or family history, metabolic health can often be measured and improved.

No ethical clinician can guarantee a specific outcome. However, when insulin resistance contributes to cognitive decline, identifying and addressing it may create meaningful opportunities to support brain function.

Next Steps

If you have Mild Cognitive Impairment, Alzheimer’s disease, memory loss, brain fog, diabetes, prediabetes, or concerns about metabolic health, do not ignore the connection between blood sugar and brain function.

The better question is not simply, “Do I have Alzheimer’s disease?”

The better question is:

Is this brain getting the energy it needs to function properly?

If you or someone you love is experiencing cognitive decline, the Carroll Institute can help you explore whether the Carroll Cognitive Method™ may be appropriate for you. We encourage you to schedule a discovery phone call to learn more.

Sources

Medical Disclaimer

This information is provided for educational purposes only and is not intended as medical advice. Individual outcomes vary. No specific result can be guaranteed. Patients should consult a qualified healthcare professional regarding their individual medical situation.

Reviewed by: Dr. Garland Glenn, DC, PhD, IFM, AFMC

Location: Sarasota, Florida

Last Updated: June 20, 2026

Dr. Garland Glenn, DC, PhD, IFM, AFMC

Founder & Clinical Director, The Carroll Institute — Sarasota, FL

Dr. Garland Glenn is a board-certified chiropractic physician and functional medicine practitioner specializing in cognitive health, neurodegeneration, and root-cause medicine. Certified as an AFMC (Advanced Functional Medicine Clinician) and Institute for Functional Medicine (IFM) trained. He has also completed over 500 hours of advanced training in Functional Neurology under Dr. Ted Carrick, founder of the Carrick Institute.

At The Carroll Institute, Dr. Glenn leads Sarasota’s only ReCODE-certified Functional Neurology program, helping patients reverse or prevent cognitive decline through the Bredesen ReCODE Protocol, neuroplasticity exercises, and personalized functional medicine care.

Learn more about his background and approach at About Dr. Garland Glenn.

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ReCODE® is a registered program developed by Dr. Dale Bredesen and licensed through Apollo Health. Dr. Garland Glenn is a certified ReCODE practitioner.

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