Okay, we're gonna get a little science-nerdy here, so hang in there with us!

We talk a lot about fueling and moving the body for longevity. But research reveals that fueling the brain is just as important—and that midlife brain health marks a critical turning point for our cognitive future. At the heart of the matter: glucose, insulin resistance, and a window of opportunity that could change how we age.

As we get older, our brain cells are at increased risk of losing access to their main energy supply: glucose. Here’s where we unpack some science:

Neuronal insulin resistance refers to changes in the brain’s ability to use glucose, which fuels cognitive functions like memory and learning. In other words, the brain is experiencing an energy shortage.

In the short term, that energy shortage may show up as brain fog, difficulty with executive functions like planning, and mood disorders, including depression. Over time, it can cause permanent damage in the form of neurodegenerative diseases like Parkinson’s and Alzheimer’s.

An important new study sheds light on a window of time where you might be able to protect your brain and keep it healthier as you age.

The Brain’s Energy Crisis: Why Glucose Metabolism Matters—Especially in Midlife

A team of researchers from the State University of New York at Stony Brook, the Mayo Clinic, Oxford University, and Harvard Medical School discovered that your 40s to 60s are a critical window for protecting your brain.

Here’s what they found: As we get older, the brain starts to struggle with energy supply. Starting around your 40s, brain cells don’t get fuel as efficiently—especially the kind of fuel they’ve relied on for decades (glucose). This makes communication between brain cells slower and shakier. The researchers describe it as a period where your brain’s systems are “bending”—feeling the strain—but haven’t yet “broken.”

But here’s the good news: they found that giving people in this age group synthetic ketones—a type of energy your body naturally produces when burning fat—helped stabilize brain cell function. Essentially, it gave those sluggish cells a cleaner, more efficient fuel source and returned them to a healthier state.

Interestingly, the same intervention done on people over 60 was not as effective. The effects “diminished markedly” in the older group, researchers observed—most likely due to advanced neuron damage. “This intervention is only effective when provided early enough for neurons to remain viable,” they noted.

In other words: Midlife is the perfect time to intervene. And metabolic health—how your body uses fuel—might be a key to keeping your brain sharper, longer.

The “Critical Window” to Preserve Cognitive Function

The study’s researchers discovered that neural insulin resistance doesn’t happen gradually, but is instead marked by two major shifts: the first in our 40s, and then another at a faster rate in our 60s.

Insulin allows brain cells to take in glucose from the blood and helps them communicate. As we age, these cells can become insulin resistant, meaning they no longer respond to insulin’s chemical signals—leading to less glucose uptake. That creates an energy shortage that, over time, causes cellular dysfunction and eventual cell death.

Previous research has shown that neural insulin resistance is amplified by lifestyle factors like eating high-fat and high-sugar diets, lack of physical activity, inflammation, oxidative stress, and mitochondrial dysfunction. It’s also more common with some genetic conditions, obesity, and Type 2 diabetes. (This has even led some researchers to refer to Alzheimer’s as “Type 3 Diabetes.”)

The study suggests that midlife is a critical window for intervention—when cells are still “bending,” not “breaking.” And interestingly, one potential therapeutic tool emerging from the research? Ketones.

Lifestyle Shifts That Protect Your Brain at Any Age

Ketones are molecules your body naturally produces when it shifts from using glucose (carbs) to using fat for fuel—usually during periods of fasting, intense exercise, or low-carb eating. They’re a cleaner, more efficient energy source for the brain, especially when glucose supply is impaired.

In this study, researchers gave adults in their 40s to 60s a synthetic ketone supplement. The ketones acted as a metabolic rescue—giving aging neurons the fuel they needed, even in the face of insulin resistance.

This is the core concept behind the ketogenic diet, a very low-carb, high-fat eating plan designed to keep the body in a state of ketosis, where it generates ketones for energy.

In clinical settings, the keto diet has been used therapeutically for nearly a century—especially in treating drug-resistant epilepsy. More recently, it’s been studied for potential benefits in Alzheimer’s, Parkinson’s, and other neurological conditions.

That said, most researchers and longevity experts agree: it’s not a one-size-fits-all lifestyle, and likely not a sustainable long-term diet for most people. The extreme carb restriction can be difficult to maintain, and for some, it can cause side effects like nutrient deficiencies, digestive issues, or hormonal disruption.

So what can you do to protect your brain health? 

8 Ways to Protect Your Brain

‍The brain needs the same longevity tools as our hearts, muscles, and bones: insulin stability and low inflammation. Here are some evidence-based strategies to support brain health at any age:

1. Limit refined carbohydrates, processed foods, and sugar
2. Eat more omega-3 fatty acids
3. Exercise regularly—combine resistance training with Zone 2 aerobic movement
4. Get 7–8 hours of sleep per night to keep inflammation in check
5. Manage stress—chronic stress can drive inflammation
6. Consider intermittent fasting to help reset insulin sensitivity
7. Try mindfulness meditation, which shows promise in improving insulin response
8. Limit alcohol consumption
   

What We’re Watching

Meanwhile, research into brain health and lifestyle interventions continues to evolve. A few promising areas we’re keeping an eye on:

• Small studies suggest medium-chain triglycerides (MCT oils) may enhance memory, though more research is needed
• The potential neuroprotective benefits of green tea

The Takeaway: Protecting your brain as you age is about being proactive. By supporting metabolic health through exercise, diet, and stress regulation, you help preserve your neural networks before they hit a tipping point. And while midlife may be the critical window for intervention, it’s never too late to align your actions with healthy intentions.