Hello,

Did you have a spooky weekend?

This is an exciting letter—the 50th one I have sent. It was also about a year ago, on November 3, 2024, that I hit send on my first Second Act Creator letter.

That first letter went to about 30 people, all of whom were friends and family. This week’s letter will go to about 2,000 people. Over the past month, 65-70% of subscribers open my emails each week (the average open rate is 38% on the newsletter platform I use). Thank you for being one of them!

I’ll admit—I’m proud to have stuck with this for a full year. Each week entails a lot of time for research and writing. But I’m glad to have done it. It has been unexpectedly satisfying to finish something every week, if that makes sense. Each week, I have to declare an imperfect draft “good enough” and hit send.

Thank you for reading each week. A special thank you to everyone who has given me feedback and encouragement. On that note - anytime you want to ask a question, send feedback, or just say hello—it's as easy as hitting reply.

OK, here’s what I have for you today:

• One big thing. Here’s your midlife training plan—not for abs, but for neurons. Find the right mix of novelty, purpose, and movement to keep your brain young and flexible.

• You have to check this out. The doctor will see you now. Plus, how long should you walk?

Let’s jump in! 🦘

1️⃣ ONE BIG THING

The Gen X guide to building a resilient brain.

This week wraps up a series of letters on how our brains work and how investing now in cognitive reserves benefits you as you age, similar to long-term financial planning.

These three letters included:

1. Your Livewired Brain - The brain isn’t fixed—it’s “livewired.” Experience sculpts both its structure and function, creating a system built to adapt throughout life.

2. Investing in Your Cognitive Reserves - Some brains stay sharp despite damage because lifelong learning, language, and social engagement build redundant neural networks that protect function.

3. Building a Brain That Ages Well - Novelty, meaning, and connection strengthen and integrate new circuits, forming a resilient network that supports cognitive reserve and healthy aging.

If you haven’t read these, they form the foundation for today’s letter, so please take a look when you can.

More specifically, last week I walked through why three specific types of activities build cognitive reserves (those that are novel, meaningful, and socially complex). Cognitive reserves are the extra scaffolding your brain builds to stay functional even when disease or decline sets in.

This week transitions to a short summary of practical applications.

I’ve summarized these into five domains, which I’ll refer to as the Five Pillars of Cognitive Reserve.

Each pillar represents a different lever for keeping your brain strong, flexible, and ready for change:

1. Seek Novelty and Challenge — spark new wiring.

2. Choose Meaningful Goals — sustain the effort to rewire.

3. Stay Deeply Social — stretch the circuits that make us human.

4. Train the Body — build the physical foundation for cognition.

5. Protect the System — restore, recover, and repair.

Notice the first three pillars align with last week’s activities, while the last two focus on core physical health for brain function.

📚Pillar 1: Seek Novelty and Challenge

Familiarity feels good — that’s why it’s tricky.

We like what we already know because it feels efficient and safe. That calm is real — the brain burns less energy when it can predict what happens next. But the trade-off is growth. Without small doses of uncertainty and challenge, the brain’s learning systems quiet down.

Novelty should be stimulating, not stressful — like steady exercise for your mind. It’s the kind of focused strain that forces new wiring but doesn’t tip into anxiety or chaos.

How to design for real novelty:

• Study something with layers. Languages, musical instruments, advanced cooking, or data analysis all engage many brain systems simultaneously.

• Travel differently. Visit a new country, yes — but also take public transit instead of renting a car, or learn a bit of the local language before you go.

• Use your hands. Woodworking, painting, gardening, or rebuilding an engine demand planning, feedback, and coordination — potent fuel for plasticity.

• Teach yourself new technology. Learn a new creative app, AI tool, or editing suite until you’re competent enough to teach someone else.

💡Science: Complex novelty releases acetylcholine and dopamine, signaling the brain to form and reinforce new circuits — the foundation of long-term adaptability and cognitive reserve.

🎯Pillar 2: Choose Meaningful Goals

Caring is the multiplier.

The brain saves what feels important. When a goal matters to you, attention remains high, and the reward system reinforces new neural pathways. Meaning turns effort into lasting change.

Pick goals that connect to identity, values, or a future you want. Give them a clear outcome and timeline so your brain can sense progress and keep investing.

How to design for meaning:

• Tie it to a real why. “Learn Spanish to live in Madrid,” not “learn Spanish someday.” Write the why where you see it daily.

• Choose a 12-week capstone. A project with a visible result: record a song, pass a language level, publish a photo portfolio.

• Build a feedback loop. Weekly milestones, practice logs, short demos for friends or a mentor. Progress signals reward and maintains plasticity.

• Make it social and useful. Teach a workshop, volunteer your new skill, or ship something others can use. Contribution deepens memory.

• Create small wins and rituals. Celebrate completions, not hours. A brief reflection after practice helps consolidate learning.

💡Science: Personally meaningful goals keep acetylcholine and dopamine levels up, solidifying new circuits. Meaning acts as the brain’s “save” function, converting effort into lasting cognitive reserve.

🤝Pillar 3: Stay Deeply Social

Your brain’s hardest workout is other people.

Every real conversation taxes memory, empathy, prediction, and language — four systems firing in tight coordination. That’s why human interaction is one of the strongest drivers of neuroplasticity and long-term brain health.

The key isn’t the quantity of contacts, but the quality of engagement. Some people thrive on a few close ties, while others need constant stimulation. What matters is active participation — listening, responding, and interpreting nuance. If you avoid social effort because it feels draining or awkward, that’s your cue: those moments are your brain’s version of resistance training.

How to design for rich connection:

• Join or build a group with stakes. Book clubs, volunteer teams, language exchanges, or any setting that demands dialogue and cooperation.

• Invest in reciprocal ties. Reach out to friends who challenge your thinking, not just those who agree with you, on a weekly basis.

• Mix generations. Mentor someone younger, learn from someone older; cognitive flexibility grows in diverse networks.

• Add social layers to learning. Take a class in person, or teach what you’re learning — explaining recruits deeper circuits.

💡Science: Complex, emotionally engaging interaction synchronizes multiple brain regions and triggers dopamine and oxytocin, reinforcing new neural pathways. Studies from Harvard and Oxford show strong, varied relationships predict slower cognitive decline and greater resilience with age.

🌉 Bridging Mind and Body

Your brain isn’t just a thinking machine — it’s a living organ, fully dependent on the body that carries it. The same blood vessels that feed your heart feed your neurons. The same recovery that rebuilds muscle helps your brain clear toxins and repair connections.

The first three pillars — novelty, meaning, and connection — train your brain to learn and adapt. Learning itself, though, depends on a stable platform: energy, circulation, sleep, and repair. Without these, plasticity slows, attention fades, and the best mental practices lose their edge.

That’s why the next two pillars shift focus from “mental workouts” to “system health.” They’re the foundation that keeps all the other work possible.

🏃‍♂️Pillar 4: Train the Body

What’s good for the heart is good for the brain.

Your brain runs on what your body delivers — oxygen, fuel, and nutrients. Every heartbeat feeds neurons. Physical training doesn’t just improve fitness; it builds the infrastructure that cognition depends on: stronger blood vessels, steadier glucose control, and more efficient mitochondria.

Movement stimulates brain-derived neurotrophic factor (BDNF) and IGF-1, growth chemicals that help neurons form new connections and repair old ones. Regular exercise also boosts blood flow, supports metabolic flexibility, and protects against the vascular decline that accelerates cognitive aging.

How to train for cognitive resilience:

• Zone 2 (steady state) cardio (3–5× per week). Fast walking, cycling, or swimming at a pace where you can talk but not sing. Builds mitochondrial and vascular capacity.

• Zone 5 (max effort) efforts (1× per week). Short sprints or hill repeats that spike heart rate and trigger the release of growth factors.

• Strength training (2× per week). Improves glucose regulation, posture, and muscle mass — all critical for healthy blood flow and brain perfusion.

• Move with complexity. Dance, martial arts, or tennis all involve balance, timing, and coordination — a double duty for both body and brain.

• Walk daily. Even light, consistent movement enhances circulation and clears mental fatigue.

💡Science: Aerobic and resistance training increase BDNF, IGF-1, and angiogenesis, improving neuronal repair and synaptic efficiency. Longitudinal studies have shown that midlife cardiorespiratory fitness is associated with a reduced risk of dementia in later life.

For more guidance on Zone 2 and Zone 5 training, see my two-part series:

1. The Gen X Guide to VO2 Max: Part 1

2. The Gen X Guide to VO2 Max: Part 2

🌙Pillar 5: Protect the System

Your brain rebuilds when you rest.

Every day, you’re wiring new connections through learning, movement, and conversation. But those changes only stabilize when you recover. Deep sleep is the body’s nightly construction crew — clearing metabolic waste, repairing neurons, and consolidating memory. Chronic stress, sleep loss, or poor metabolic health can interrupt this process, leaving the system partially rebuilt.

When you sleep, cerebrospinal fluid flushes debris from brain tissue, cortisol levels reset, and growth hormones rise. Consistent sleep also helps maintain steady glucose and blood pressure levels — both of which are crucial for preserving the small vessels that supply the brain. Stress management works through the same pathways: by lowering chronic inflammation, protecting the hippocampus, and restoring balance to the autonomic nervous system.

How to protect and restore your system:

• Prioritize sleep like training. Aim for 7–9 hours of sleep; finish meals at least two hours before bedtime; keep the room dark, cool, and quiet.

• Anchor your circadian rhythm. Get bright light in your eyes within an hour of waking; keep a consistent sleep–wake schedule, even on weekends.

• Use short recovery sessions. A 10-minute walk, breathing session, or quiet break can lower cortisol levels and improve focus.

• Train metabolic stability. Maintain healthy blood pressure, blood sugar, and body composition — the foundation for vascular and cognitive health.

• Track your signals. Morning grogginess, mood swings, or brain fog aren’t moral failures; they’re metrics. Adjust recovery before you push harder.

💡Science: Deep sleep activates the brain’s glymphatic system, clearing waste proteins linked to cognitive decline. Chronic stress elevates cortisol levels, which can lead to a reduction in hippocampal volume over time. Studies have shown that consistent sleep quality, emotional regulation, and metabolic control are strong predictors of cognitive longevity.

BONUS: Peter Attia’s Ask Me Anything on Brain Health

This is Episode 251 of Attia’s podcast The Drive. It covers optimizing brain health: Alzheimer’s disease risk factors, APOE, prevention strategies, and more.

It includes a key element I have not covered in my letters—the genetic risk factors for Alzheimer’s disease (APOE gene variants). I have tested for this myself, and recommend it. As with any test like this, getting the results can be scary, and you need to be sure you are ready to hear the results. So of course, this is a personal decision.

Listen to the episide by clicking below:

Thanks for reading this week. It means a lot to me.

Have a great week.

Kevin

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