Have you ever heard someone call Alzheimer’s disease “Type 3 Diabetes”?
It sounds convincing. For years, scientists have known that brains affected by Alzheimer’s are swimming in unused sugar, yet the brain cells (neurons) are literally starving to death. For a long time, doctors figured this meant the brain had just become “insulin resistant”—meaning it forgot how to process sugar, just like what happens in the body with normal diabetes.
But guess what? Exciting new research shows that this old theory could be totally wrong.
Alzheimer’s isn’t a sugar-processing failure. It is actually a disease of inflammation — first and foremost. What looks like diabetes is actually a massive, immune system hijack driven by chronic inflammation. Your brain’s defense force goes into overdrive, causing slight to increasing swelling (inflammation) which, in turn inadvertently prevents your neurons from being able to feed on the glucose that the body keeps sending to the brain.
The net result: your brain cells (neurons) begin starving. And if we don’t interrupt this cycle, they will eventually starve to death.
Here is how the brain’s protective forces can cause it to kill itself. You may want to read on…
The Blood-Brain Barrier, Inflammation, and the Aging Brain
To understand what is happening, we have to look at the Blood-Brain Barrier (BBB). Think of it as a super-strict army of guards that protect our brain. When we are young, the chain of army guards is unbreakable. They selectively let in fuel (like oxygen and sugar/glucose) but completely block out bad guys like viruses, bacteria, and fungi.
But as our brain gets older, its protective guards figuratively begin to retire or quit, causing the protective wall called the blood-brain barrier to leak. The older we get, the more guards leave their post. And with their absence comes the very real risk for larger and larger things to make their way into our brain.
Not to worry quite yet – because the brain does have other soldiers inside – which is covered in another blogpost you can access here: Could Alzheimer’s Be the Brain’s Response to Infection?
The Small Leak (= short term brain fog)
At first, the leak is tiny. If a middle-aged adult – say someone in their 40’s gets a standard cold or a urinary tract infection, the physical microbes (virus/bacteria) are still forced to stay down in the body. However, tiny immune warning signals from the microbial infection slip past the BBB army of guards and enter the brain.
This triggers a small bit of inflammation in the brain, which is often referred to as a temporary “brain fog.” You feel off, tired and a bit confused. The confusion is stemming from the inflammation and interferes with your ability to think clearly—which is why we call it a “fog.” Likened to a fog where you can’t see clearly, brain fog is where you can’t quite think clearly.
For a middle-aged person, this is a short-term phenomena, that resolves once the body has beaten the illness. And once you’re body is feeling better, your thinking returns to normal. This is because the slight amount of brain inflammation has slowly resolved. The key here is that the “swelling” in the brain is ever so slight because your brain’s own surveillance has everything under control. Some of us don’t even notice it as we are sleeping so much. Which is exactly how it should be.
The Big Leak (= longer term neuroinflammation)
For the older person, whose blood-brain barrier has now been losing more and more of its “guards”, there are now much larger holes of exposure. Now, the guards aren’t just letting warning signals slide by—they are letting the actual bad guys march straight inside. Large, nasty invaders like whole virus, bacteria or fungi cells have the potential to slip directly into the brain’s main tissue.
This is where the “brain fog” moves beyond being temporary. And this can result in agitation and frustration because now you’re really noticing a sense of being off and confused. If this state of brain fog doesn’t clear up after a week, it means the brain has transitioned through a hidden timeline that directly impacts the workhorses of the brain—the neurons:
Hours 1 to 24 (Neuron's Unite):
The invaders get past your BBB guards and enter the brain. Sensing immediate danger, your neurons take over.
This is where our story returns begins to challenge the idea that Alzheimer’s might be related to a Diabetic state in the brain: To take on the assault themselves, your neurons desperately need more energy (glucose/sugar) to survive the ongoing attack, so they call up their entire internal support team (scientifically referred to as GLUT3 transporters, we’ll call them the “Glucose Hunters”). These Hunters living within the neuron rush to its surface and begin to frantically beg and steal all glucose (for energy) around the neuron so the neuron can stay strong while under attack. This sudden, massive spike in brain stress manifests as a sudden wave of heavy confusion to you as all you know is that you are physically unwell. Behind the curtain your brain’s taking a hit as well.
Days 2 to 4 (The Hijack):
Because your body’s own immune system hasn’t stopped the infection in your body, those invading virus, bacterial or fungal cells just keep coming in!
Your brain is still in control at this point. Your neurons which have been feeding on glucose now shift into high gear and send out signals to the brain’s heavy-duty immune cells (microglia). These heroes also need extra energy (glucose) themselves to perform their cleanup duties, and unfortunately, they actually begin stealing the glucose surrounding your neurons – which causes your neurons to begin to starve.
Just like your neurons, the microglia have their own internal support team (scientifically called GLUT1 transporters, we like to call them the “GLUCOSE HOGS” 
And because they are now there to defend your neurons, unfortunately, your neurons have to wait their turn to get their badly needed glucose while this high-level, inflammatory attack they actually organized takes place.
Day 7 and Beyond (The Locked Loop):
If we don’t interfere by shutting off the origin of the infection that stems from the body, the brain’s protective defenses begin to collapse.
Your neurons can go without glucose for a bit, but they are simply NOT built to withstand the intense, inflammatory stress that comes with a battle lasting longer than a week. Under this relentless assault, the neurons become deeply damaged. They can no longer signal to their internal support team—the “Glucose Hunters”— that they need to get back to eating glucose … meaning your weakened neurons have completely lost the ability to capture glucose for energy.
The Ultimate Puzzle: If the Glucose Hogs are eating sugar, why do we still find pools of unused glucose everywhere?
To understand this, you have to know that your body’s blood vessels are programmed to deliver a massive, non-stop conveyor belt of sugar to your brain every single second. The blood vessels don’t know there is a siege going on; they just keep pushing food (glucose) into the brain. Because the immune cells are relatively small, local army units, they only eat the sugar right inside their specific battle zones.
Meanwhile, the damaged neurons all across the brain have lost their Glucose Hunters and can’t touch a single drop of the delivery. And because the conveyor belt keeps running, yet the cells can’t eat, sugar (glucose) begins to pile up in the brain.
Does this extra sugar cause damage? Yes, but not in the way you might think.
Inside the brain, the pooling glucose undergoes a chemical glitch and starts mutating into sticky, toxic proteins. And when the brain’s immune cells detect these weird, mutated sugar-proteins, they panic. They assume there is a whole new threat and begin producing Reactive Oxygen Species (ROS)—which are essentially chemical explosives meant to neutralize the threat.
So, instead of cleaning up the sugar, these massive bursts of ROS end up causing massive collateral damage, scorching the already-starving neurons and sending inflammation through the roof.
DX: Alzheimer's Disease
At this point, we will be diagnosed with Alzheimer’s. Our ability to concentrate is severely challenged—due to all the inflammation. Our resilient brain is losing its ability to redirect signals past weak or dying neurons—which is starting to impair our ability to recall things. Our daily life is now becoming affected.
And because the neurons are too weak to send out the “off” switch signals to stop the immune cells, the battle never ends. As your neurons starve and get hit by the immune crossfire, they begin to wither and die, locking the brain-fog confusion into a permanent, worsening cycle.
The Hidden Culprits: Chronic Low-Grade Infections
When people think of dangerous brain infections, they think of dramatic illnesses like meningitis. But in older adults, the “Big Leak” is usually triggered by quiet, everyday culprits that go completely ignored.
Chronic, low-grade infections—like long-standing gum disease or a stubborn, untreated sinus infection—act like a constant drip-irrigation of bacteria directly into the bloodstream. Because the aging blood-brain barrier has large holes, these everyday bacteria slowly and continuously migrate into the brain, causing a constant state of low-grade inflammation.
If an older adult has brain confusion that lingers for weeks or months, it isn’t just “normal aging.” It is a major red flag that a hidden, chronic infection is actively forcing their brain into a permanent, glucose-starving loop.
The Twist: Why Diabetics Are Still at Risk
If Alzheimer’s isn’t actually a form of diabetes, why do people with diabetes still have a much higher risk of developing it?
The answer comes down to plumbing, not sugar.
Diabetes doesn’t magically transport extra, toxic sugar into your brain cells to cause Alzheimer’s. Instead, chronic high blood sugar damages the body’s blood vessels. When the tiny, delicate blood vessels in the brain get damaged and clogged, they lose their ability to deliver vital oxygen to the brain.
Without enough oxygen, our blood-brain barrier breaks down even faster, opening the floodgates for the microbial invasions that trigger the chronic inflammation and immune hijack in the first place. Plus, diabetics are at an extremely high risk of developing gum infections.
So, while diabetes can pave the road to Alzheimer’s by damaging the brain’s plumbing, the ultimate destruction of the brain isn’t a metabolic sugar glitch—it is an immune system war gone rogue.
A Note from the Foundation
Disclaimer: this post should not be taken as professional medical advice. Always consult with a qualified healthcare professional regarding any medical condition or treatment plan.
This post is entirely based on exciting, emerging science regarding the role of neuroinflammation and the blood-brain barrier. This cutting-edge model is actively being explored by the Alzheimer’s Legacy Research Lab, which is proudly funded by my foundation: The Curing Alzheimer’s Disease Foundation. We believe that by understanding how the brain fortress actually functions, we can unlock real, actionable ways to prevent and defeat this devastating disease.
