Living a moderately active lifestyle can promote brain health. (Inside Creative House/Shutterstock)

In a nutshell

Both too little and too much exercise can accelerate brain aging. The study found a U-shaped relationship where people who were sedentary and those who exercised excessively both showed signs of older-looking brains compared to moderate exercisers.

Moderate physical activity appears optimal for brain health. People who engaged in moderate amounts of light, moderate, or vigorous exercise had the youngest-looking brains, regardless of the specific intensity level.

This challenges the “more is always better” exercise mindset. While most people still need to move more, the research suggests there may be diminishing returns or even potential harm from extreme exercise levels when it comes to brain health.

HANGZHOU, China — When it comes to keeping your brain young, there’s a sweet spot for how much exercise you get. Get too little physical activity and your brain ages faster. Get too much, and the same thing happens.

A new study from China of nearly 17,000 people found that both couch potatoes and extreme fitness enthusiasts showed signs of accelerated brain aging compared to those who exercised in moderation. Using advanced brain imaging and wearable fitness trackers, researchers discovered what they’re calling a “U-shaped” relationship between physical activity and brain health, meaning the brain benefits peak somewhere in the middle, not at the extremes.

This research, published in Health Data Science, challenges the common belief that more exercise is always better for your brain. While we’ve long known that sedentary lifestyles are bad for cognitive health, this research suggests that excessive exercise might actually harm your brain through different biological pathways.

The research team, led by scientists at Hangzhou Normal University in China, used data from the UK Biobank, one of the world’s largest health databases. They analyzed brain scans and fitness tracker data from 16,972 adults between ages 37 and 73, with a median age of 62. About 55% of participants were women, and the vast majority (97.6%) were white.

Those who participated in moderate exercise showed better brain health in the study. (Mladen Zivkovic/Shutterstock)

To determine “brain age,” researchers fed over 1,400 different brain measurements into a sophisticated computer algorithm called LightGBM. This artificial intelligence system learned to predict someone’s chronological age based solely on their brain structure. When the predicted “brain age” was higher than someone’s actual age, it suggested accelerated brain aging.

Study participants wore wrist-mounted accelerometers, devices similar to fitness watches, for seven straight days to objectively measure their physical activity. The devices tracked everything from light activities like casual walking to vigorous exercise like running or high-intensity workouts.

Finding the Sweet Spot for Brain Health

Results revealed an interesting pattern across all types of physical activity. Whether researchers looked at light, moderate, or vigorous exercise, they found the same U-shaped curve: people who did very little activity showed signs of brain aging, those who did moderate amounts had the youngest-looking brains, and those who exercised excessively also showed accelerated aging.

For context, the median weekly activity levels were about 34 hours of light activity (like slow walking), 7.7 hours of moderate activity (like brisk walking), and just 20 minutes of vigorous activity (like running or intense sports). People in the highest activity quartiles were significantly more active than these medians, while those in the lowest quartiles did much less.

Brain age differences were modest but statistically significant. While the absolute differences were small, they could potentially be meaningful for long-term cognitive health, especially when considering that brain aging is linked to various cognitive disorders.

Why Exercise Extremes Might Harm Your Brain

Biological mechanisms behind this U-shaped relationship aren’t fully understood, but researchers have theories based on previous studies. For people who exercise too little, physical inactivity reduces blood flow to the brain and decreases production of brain-derived neurotrophic factor, a protein crucial for maintaining healthy neurons.

But excessive exercise presents a different theoretical problem. The researchers suggest that extreme physical activity might trigger oxidative stress and inflammatory responses in the brain, potentially accelerating the aging process, though this needs further investigation.

Brain aging also partially explained the relationship between physical activity and cognitive function. People with older-looking brains performed worse on cognitive tests and had higher rates of brain-related disorders like dementia and depression.

These results show that extreme exercise doesn’t mean pristine brain health. (Photo by Pixabay on Pexels.com)

The study didn’t just look at overall brain aging; it examined specific brain regions and structures. Researchers found that moderate physical activity was associated with better preservation of white matter (the brain’s “wiring”) and certain key regions involved in memory and thinking.

People who exercised moderately had less white matter damage and better-preserved volumes in critical brain areas like the caudate and putamen, regions important for movement control and cognitive function.

Brain imaging revealed that both insufficient and excessive activity were linked to similar patterns of structural changes, suggesting they might harm the brain despite having different underlying causes.

What This Means for Your Workout Routine

For most Americans, this research probably isn’t a reason to dial back exercise; the bigger public health problem remains physical inactivity. The study’s “excessive” exercisers were likely in the top tier of fitness enthusiasts, doing far more activity than the average person.

However, findings do suggest there might be diminishing returns to extreme exercise when it comes to brain health. Weekend warriors who cram intense workouts into their schedules might benefit from spreading activity more evenly throughout the week.

Previous studies relied on people’s own reports of their activity levels, which can be notoriously unreliable. By using wearable devices, this study captured a more accurate picture of real-world movement patterns.

Still, the research is just a snapshot in time rather than a long-term study, so it can’t prove that exercise levels directly cause changes in brain aging. The study population was also predominantly white and British, which may limit how well findings apply to other groups.

The perfect amount of exercise for brain health probably varies from person to person based on factors like age, genetics, and overall health status. But this research suggests that for most people, consistent moderate activity—rather than extreme fitness regimens—may be the key to keeping our brains young.

Like Goldilocks searching for the perfect porridge, when it comes to exercise and brain health, “just right” appears to be somewhere in the middle—not too little, not too much, but a sustainable amount that keeps both body and mind functioning at their best.

Paper Summary Methodology

Researchers analyzed data from 16,972 participants in the UK Biobank, a large health database. Participants wore wrist-mounted accelerometers for seven consecutive days to objectively measure physical activity across light, moderate, and vigorous intensity levels. Scientists used brain MRI scans and fed over 1,400 brain measurements into a machine learning algorithm called LightGBM to predict “brain age.” The difference between predicted brain age and chronological age created a “brain age gap” measure, where positive values indicated accelerated brain aging.

Results

The study found U-shaped relationships between all types of physical activity and brain aging, meaning both insufficient and excessive exercise were associated with older-looking brains compared to moderate activity levels. The brain age prediction model achieved high accuracy with a correlation of 0.90 after corrections. Mediation analysis showed that brain age gaps partially explained the relationships between physical activity and cognitive function, as well as brain-related disorders like dementia and depression.

Limitations

The study’s cross-sectional design prevents establishing causality between exercise levels and brain aging. The participant population was predominantly white (97.6%) and British, potentially limiting generalizability to other demographic groups. The UK Biobank’s low response rate (5.5%) and healthy volunteer effect may not represent the broader population, though researchers note this likely has minimal impact on association strength estimates.

Funding and Disclosures

This research was supported by the National Natural Science Foundation of China (grant 72204071), the Zhejiang Provincial Natural Science Foundation of China (grant LY23G030005), and the Scientific Research Foundation for Scholars of HZNU (grant 4265C50221204119). The authors declared no competing interests.

Publication Information

The study “Accelerometer-Measured Physical Activity and Neuroimaging-Driven Brain Age” is authored by Chen, H., Cao, Z., Zhang, J., Li, D., Wang, Y., & Xu, C. It was published in Health Data Science (5, Article 0257) on May 2, 2025.