brain health · Apr 08, 2025

Type 3 Diabetes: The Hidden Link Between Alzheimer’s and Metabolic Health

elderly man wearing herringbone blazer and messenger cap standing in front of turquoise wall

By Natalie Falshaw, MSc

Alzheimer’s disease is a devastating neurodegenerative disease that erodes memory, cognition, and independence. With no cure—only treatments that may slow its progression—prevention is our best weapon.

While it’s often associated with aging, recent research suggests that brain changes that lead to Alzheimer’s actually begin decades before symptoms appear, highlighting the disease’s chronic nature [1]. Understanding the mechanisms that drive this risk is key to stopping the disease in its tracks or preventing symptoms from getting worse.

One emerging area of research is the strong connection between Alzheimer’s and type 2 diabetes, revealing a deeper link between metabolic health and brain function. But why does this connection exist, and, more importantly, what can you do to reduce your risk? This article explores how blood sugar regulation influences brain function and examines the role of diet, lifestyle, and cutting-edge treatments that could help safeguard your brain for the long haul.

What Is Alzheimer’s Disease?

Alzheimer’s is a complex brain disorder that affects nearly seven million Americans every year — a number which is expected to double to 14 million by 2060. Influenced by both genetics and lifestyle factors, Alzheimer’s hallmark pathological changes in the brain include [2]:

Abnormal protein accumulation: Amyloid plaques and neurofibrillary tangles build up in and around neurons, disrupting communication and triggering cell death.
Neurotransmitter imbalances: Dysregulation of key brain chemicals, including acetylcholine, which impairs memory, learning, and cognitive processing.
Brain atrophy: Progressive shrinkage of brain tissue, particularly in areas critical for memory, such as the hippocampus.

These neurodegenerative changes lead to progressive cognitive decline and dementia. According to the Alzheimer’s Association, early signs include [3]:

Persistent memory loss that disrupts daily life
Difficulty solving problems or making decisions
Struggling with routine tasks that once felt automatic
Confusion about time, place, or familiar environments
Trouble understanding or using language, both written and spoken
Frequently misplacing items and being unable to retrace steps
Poor judgment in decision-making
Withdrawal from work, hobbies, or social interactions
Noticeable mood swings or personality changes

It’s natural for memory and cognitive abilities to shift with age, but when those changes start to feel more pronounced or concerning, you shouldn’t ignore them. If you or someone you care about is going through this, know that you’re not alone. Speaking with a doctor can provide the clarity and support you or your loved one needs to move forward.

Type 3 Diabetes: How Insulin Resistance Affects Brain Function

What occurs and triggers the onset of Alzheimer's symptoms is still being studied. However, one major emerging factor is insulin resistance, which is clearly linked to prediabetes and type 2 diabetes diagnoses [4].

To understand this, let’s first contrast type 1 and type 2 diabetes and define the role of insulin in the body:

Type 1 diabetes is an autoimmune disease in which the body attacks insulin-producing cells in the pancreas, leading to a complete lack of insulin.
Type 2 diabetes develops when the body produces insulin, but cells no longer respond effectively to its signal as they’ve become resistant.

Think of insulin as a key that unlocks the doors of your cells, allowing glucose (a sugar found in carbohydrates, which is your body’s primary source of energy) to enter and be used for energy. In type 1 diabetes, there aren’t enough keys (insulin deficiency), whereas in type 2 diabetes, the keyholes are jammed or broken (insulin resistance), preventing glucose from entering cells. In both cases, as a result, glucose remains trapped in the bloodstream instead of fueling cells, leading to symptoms like excessive thirst, frequent urination, fatigue, blurry vision, and an increased risk of serious complications if left unmanaged.

Although “type 3 diabetes” is not an officially recognized medical diagnosis, the term—first proposed by researchers in 2005—has gained traction due to the similar metabolic disturbances seen in both Alzheimer’s and diabetic patients [5]. Type 3 shares more in common with type 2 diabetes but specifically refers to insulin resistance in the brain.

The brain, like most organs, relies heavily on glucose for energy, and insulin is essential for getting that glucose into brain cells [6]. When insulin signaling becomes impaired, brain cells struggle to access the fuel they need, potentially contributing to cognitive decline, neurological dysfunction, and psychiatric symptoms—mirroring the systemic metabolic issues seen in diabetes.

When the brain loses its ability to properly respond to insulin, it leads to:

Reduced glucose uptake: Brain cells struggle to access the fuel they need for energy.
Cerebral glucose hypometabolism: The brain experiences a chronic energy deficit, impairing function [7].
Neurodegeneration: Without enough energy, neurons, especially in the hippocampus, the region responsible for memory and learning, weaken and die, leading to cognitive decline [8].
Inflammation and oxidative stress: Insulin resistance contributes to harmful cellular stress and inflammation, worsening brain function.

This metabolic dysfunction may accelerate the development of Alzheimer’s—explaining why people with type 2 diabetes are significantly more likely to develop dementia.

In fact, the connection between diabetes and dementia is striking:

People diagnosed with type 2 diabetes before age 50 may nearly double their risk of developing dementia later in life [9].
Up to around 81% of Alzheimer’s patients also have type 2 diabetes or prediabetes, highlighting a clear metabolic link.
Insulin resistance, a hallmark of type 2 diabetes, has been found in the brains of Alzheimer’s patients—even those without diagnosed diabetes [10].

So, if type 2 diabetes is a major risk factor for Alzheimer’s, what can you do about it [11]?

What Causes Type 3 Diabetes?

So, to summarize what we’ve learned so far, here are some key definitions:

Alzheimer’s disease: A progressive neurodegenerative disorder characterized by memory loss, cognitive impairment, and brain atrophy, often associated with the buildup of abnormal proteins.
Insulin resistance: A condition where cells become less responsive to insulin, preventing glucose from entering cells efficiently.
Type 3 diabetes: A term used to describe insulin resistance in the brain, which may contribute to Alzheimer’s disease by impairing brain energy supply and triggering neurodegenerative changes.

Although insulin resistance appears to play a significant role in Alzheimer’s risk, it is not the sole cause. Some cases of Alzheimer’s occur independently of insulin dysfunction, such as inheriting certain genes, like APOE4, which significantly raises Alzheimer’s risk [12].

However, scientists are still working to unravel the full connection between metabolic health and neurodegeneration and research suggests that many of the same metabolic disturbances underlying type 2 diabetes—such as chronic inflammation, impaired glucose regulation, and vascular damage—also play a role in Alzheimer’s. Therefore, it is unsurprising that both conditions share several non-modifiable and modifiable risk factors.

Risk factors that can’t be changed (but increase the risk of type 2 and type 3 diabetes) include:

age (risk increases with age),
genetics, and
ethnicity (South Asian, African, and Hispanic populations have a higher predisposition to insulin resistance) [13].

Fortunately, many risk factors can be influenced by lifestyle choices, meaning prevention is possible [14]. Key drivers of both type 2 diabetes and Alzheimer’s that you have control over include:

Obesity: Excess body fat, particularly visceral fat, contributes to metabolic dysfunction [15].
Hypertension: High blood pressure in midlife is strongly linked to other chronic diseases.
Poor diet: Diets high in refined carbohydrates, added sugars, and ultra-processed foods drive insulin resistance in the brain and body [16].
Physical inactivity: A sedentary lifestyle increases the risk of both diabetes and Alzheimer’s [17].
Chronic inflammation: Drives both metabolic disease and neurodegeneration.
Depression and loneliness: Both have been associated with a higher risk of metabolic dysfunction [18].
Smoking and air pollution: Both are associated with higher dementia and diabetes risk [19].

Understanding how blood sugar and insulin imbalances contribute to cognitive decline and Alzheimer’s risk opens new avenues for prevention and treatment of both type 2 and type 3 diabetes simultaneously.

How to Support Your Brain and Metabolic Health

Since type 3 diabetes isn’t a recognized condition, there is no official treatment. However, addressing metabolic dysfunction can benefit both diabetes and Alzheimer’s prevention.

Lifestyle interventions that may help reduce the risk of insulin resistance include:

1. Optimize body composition

Build lean muscle mass through resistance training and reduce excess body fat, especially visceral fat, to improve metabolic health. Supplements like Motus, formulated with synergistic ingredients such as Berbevis, ALA, taurine, and Siliphos to support metabolic function, may offer an additional route to improving body composition. In fact, Motus has demonstrated strong clinical efficacy in animal models, showing benefits such as fat loss, improved lipid profiles, and balanced metabolic hormones like GLP-1 [20].

2. Improve your diet

Prioritize whole, unprocessed foods, minimize added sugars and refined carbs, and include healthy fats like omega-3s to support brain and metabolic health [21]. Our dietitian-approved grocery list for weight loss is a great starting point for anyone looking to eat a metabolically healthy diet.

3. Exercise regularly

Both aerobic exercise and strength training enhance insulin sensitivity and overall metabolic function. Research suggests that doing a mix of half aerobic exercise and half resistance training (30 minutes of each at least three times per week) is most effective at improving metabolic health [22].

4. Support brain care

Engage in mentally stimulating activities, prioritize quality sleep, manage stress effectively, and consider cognitive-supporting supplements like Nouro. Developed alongside Duke Health, Nouro’s novel blend of synergistic natural ingredients has clinically proven benefits, such as reducing hippocampal shrinkage and preventing abnormal protein formation. [23, 24].

Although these strategies aren’t cures, they highlight empowering ways to support brain health and prevent cognitive decline. Always consult with a healthcare professional before making significant changes.

Takeaways

While age and genetics play a role in Alzheimer’s, there is growing evidence that metabolic health is a major modifiable factor. The connection between insulin resistance and cognitive decline suggests that supporting blood sugar regulation may be a powerful way to protect your brain, and simple lifestyle changes can make a real difference in protecting your long-term cognitive function.

References:

Natalie is a health researcher, consultant, and coach, dedicated to empowering individuals with evidence-based insights into their unique biology. With a BSc in Neuroscience (University of Leeds) and an MSc in Microbiome Research (King’s College London), she specializes in metabolic health, longevity, and the microbiome, translating complex research into actionable knowledge for disease prevention.

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