A massive study just found that exercise doesn't actually make your brain bigger or sharper—everything we thought about it might be backward.
March 25, 2026
Original Paper
The effect of physical activity on brain structure and cognitive function in the population-based cohort of LIFE-Adult-Study
medRxiv · 2025.10.23.25338642
The Takeaway
Contrary to the belief that exercise keeps the brain young and grows the hippocampus, this analysis of over 2,500 adults found no link between activity levels and brain structure. The researchers suggest 'reverse causation'—it is not that exercise creates a healthy brain, but that people with healthier brains are more capable of staying active.
From the abstract
Physical activity is believed to positively influence brain health and cognition and is considered a modifiable lifestyle factor that may protect against cognitive decline and neurodegeneration. In this observational study, we investigated the cross-sectional and longitudinal effects of self-reported total and moderate-to-vigorous physical activity on cognitive scores on the Trail Making Test (TMT-A and TMT-B), hippocampal volume, and BrainAGE, in a large population-based cohort from the LIFE-Ad