Your Brain Can Actually Grow. Here's How

Most people think about exercise in terms of what it does to their body like burning calories, building muscle, losing weight. Fair enough. But what if I told you that going for a brisk walk three times a week could also physically grow your brain?

Not metaphorically. Literally grow it.

This might sound like something out of a science fiction movie, but it's one of the most well-replicated findings in neuroscience. And understanding it might just change how you think about exercise forever.

The Brain's Most Vulnerable Neighbourhood

Deep inside your brain sits a small, curved structure called the hippocampus. Think of it as your brain's memory hub, it's central to learning, storing new information, and navigating space. It's also one of the first regions to deteriorate as we age.

Here's the uncomfortable truth: the hippocampus shrinks by roughly 1–2% every year in healthy older adults. That gradual loss is directly linked to the kind of memory problems people start noticing in their 50s and 60s, forgetting where you put things, losing track of conversations, struggling to learn new skills. Left unchecked, it increases the risk of dementia.

For a long time, scientists assumed this was simply inevitable. Part of getting older. Something to be managed, not reversed.

They were wrong.

What the Research Found

A landmark study by Erickson and colleagues put 120 older adults who were all sedentary at the start, into one of two groups for a year. One group did moderate aerobic exercise three times a week (walking, building up to 40 minutes per session). The other did stretching and toning as a control.

Brain scans told a very interesting story. The aerobic exercise group grew their hippocampus by around 2% over the year. The stretching group, by contrast, lost about 1.4% which was right in line with normal ageing.

That 2% gain effectively reversed one to two years of age-related brain shrinkage. Not slowed it. REVERSED IT!!!

The researchers also tracked a protein called BDNF (sometimes called "Miracle-Gro for the brain") which plays a key role in generating new brain cells. Higher BDNF levels tracked closely with greater hippocampal growth in the exercise group, suggesting this is one of the main biological pathways at work.

What type of exercise caused this? Just moderate-intensity aerobic activity. Not marathon training. Not an extreme programme. Walking.

What It Means for You In Practice?

This study was done with older adults, but the implications stretch across every age group. The hippocampus doesn't suddenly start shrinking at 65, the process begins earlier, and so does the opportunity to protect it.

Here's what the evidence translates to in practical terms:

Cardio is non-negotiable for brain health. Strength training has enormous benefits, and I'd never tell you to skip it. But if you've been skipping your aerobic work because it feels less glamorous than lifting, this is your reason to bring it back. Three sessions a week of moderate-intensity cardio — where you're slightly breathless but can still hold a conversation — appears to be the sweet spot.

You don't need to go hard. The participants in this study walked. They weren't running intervals or grinding through HIIT classes. Moderate effort, consistent frequency, sustained over time, that's the formula.

It's never too late to start. This is perhaps the most important finding. These participants were sedentary before the study began. Their brains still responded. Starting an exercise routine in your 50s, 60s, or beyond is not futile, the research is clear that meaningful gains are possible.

Memory and focus are trainable. Better hippocampal volume was directly linked to better spatial memory performance. This means the physical changes in the brain translated into real cognitive improvements and not just numbers on a scan.

If you're already exercising regularly, this is validation that what you're doing matters in ways that go well beyond the mirror. If you're not, consider this your most compelling reason to start.

What "40-Minute Brisk Walk" Actually Looks Like in Practice

As I said, the key is hitting moderate intensity, which the study used and which is defined as 50–70% of your maximum heart rate. Here's how to find that for yourself and what it translates to on the ground.

Step 1 — Find Your Target Heart Rate Zone

Your maximum heart rate is roughly 220 minus your age. You want to stay between 50–70% of that number during your walk.

Age	Max HR	Target Zone (50–70%)
40	180 bpm	90–126 bpm
50	170 bpm	85–119 bpm
60	160 bpm	80–112 bpm
70	150 bpm	75–105 bpm

No heart rate monitor? Use the talk test: you should be able to hold a conversation but have to pause every sentence or two for breath. If you can sing, go faster. If you can't get more than three words out, slow down.

Step 2 — Speed

Outdoors or on a treadmill, you're aiming for roughly 5–6.5 km/h (3–4 mph). That's faster than a casual stroll but nowhere near a jog.

A simple real-world anchor: if you're covering 1 km in about 10–12 minutes, you're in the right zone. Most people find this feels like "walking with purpose", the pace you'd use if you were slightly late to a meeting.

Step 3 — Elevation

This is where most people leave results on the table. Flat walking at 5 km/h often isn't enough to push you into the moderate heart rate zone, particularly if you're reasonably fit. Adding incline fixes that without any extra impact on your joints.

Outdoors: Look for a route with gentle hills. Even a 5–8% gradient (a moderate street hill) makes a meaningful difference. You'll feel your glutes and calves engage and your breathing deepen — that's the zone you want.

On a treadmill:

• Start at 1–2% incline to simulate outdoor walking (flat treadmills are slightly easier than real flat ground due to the belt moving under you)

• If you're still comfortable at your target speed, increase to 3–5% incline

• A 2–7% incline increases heart rate by almost 10% compared to flat surface walking, which for many people is exactly the nudge needed to reach the moderate intensity zone without speeding up.

If you're leaning on the treadmill handrails for support, the incline is too steep so drop it down. Holding the rails defeats the purpose and reduces the effectiveness of the workout.

Step 4 — The 40-Minute Structure

Don't just launch into 40 minutes at full pace. Here's a practical breakdown:

Minutes 0–5: Warm-up. Walk at your normal comfortable pace, flat or 1% incline. Let your body ease in.

Minutes 5–35: Working phase. Hit your target speed (5–6.5 km/h) and incline (3–5% if on a treadmill, hills if outside). Aim to stay in your heart rate zone. This is where the brain benefits happen.

Minutes 35–40: Cool-down. Drop the incline to zero, slow your pace, let your heart rate come back down gradually.

What If You're Just Starting Out?

Don't try to do 40 minutes immediately. The participants in the study built up to it progressively over seven weeks: starting at just 10 minutes per session and adding 5 minutes each week. That's the honest version of the protocol.

A realistic starter plan (if you are a beginner):

• Week 1–2: 15 minutes, flat, 4.5–5 km/h

• Week 3–4: 20–25 minutes, introduce 1–2% incline

• Week 5–6: 30 minutes, 3% incline

• Week 7+: 40 minutes, 3–5% incline, full target heart rate zone

Here is a fast tool that will help you get started:

Outdoor vs. Treadmill — Does It Matter?

Not for the brain benefits. Walking at low to moderate intensity demonstrated favorable efficacy for increasing BDNF levels regardless of setting. The treadmill just makes it easier to control your exact speed and incline consistently. Outdoors adds the bonus of natural environment exposure, which has its own mental health benefits. So both work, don't complicate your life, the best one is whichever you'll actually do three times a week.

Quick Takeaways

• Try adding three sessions of moderate aerobic exercise per week: a 40-minute brisk walk is enough to make a measurable difference to your brain.

• Remember that brain shrinkage with age is not inevitable and consistent cardio has been shown to physically reverse it.

• Focus on consistency over intensity. The brain benefits came from sustained, moderate effort and not extreme training.

• Know that it's never too late to start. Previously sedentary adults grew their hippocampus within a year of beginning a walking programme.

That's all for me today. Remember, if you need extra help, support and coaching from me, you can book a consult here. See ya!!