Summary
Neuroscientist and professor Shane O'Mara, author of "In Praise of Walking," joins Dhru Purohit to explain why walking is fundamental to brain health and longevity. O'Mara argues that the brain exists primarily for movement, noting that trees and plants have no brains because they don't move. He presents evidence that hitting 7,500+ steps per day reduces all-cause mortality by 30-70%, while non-mechanized societies walking 14,000-18,000 steps daily show remarkably low rates of chronic disease and cardiovascular health comparable to 40-year-olds at age 80. The conversation covers walking's impact on brain aging, showing that regular walkers experience hippocampal growth and improved memory while sedentary individuals show decline. O'Mara notes that 40% of dementia cases could be prevented by behavioral changes, with activity level being a key modifiable factor. He explains the mechanisms through BDNF production, myokine release from muscles, and how standing and walking challenge the vestibular system. The episode also explores creative walking (citing Kant, Darwin, and Hamilton), social walking as "collective effervescence," post-meal walking for blood sugar control, and practical tips for adding 5,000 steps to your current daily baseline.
Key Points
- Hitting 7,500+ steps per day reduces all-cause mortality by 30-70% depending on the study
- Add 5,000 steps above your current daily average as a practical starting target
- Non-mechanized societies walk 14,000-18,000 steps daily with remarkably low chronic disease rates and the cardiac health of a 40-year-old at age 80
- 40% of dementia cases could be prevented through behavioral changes, with physical activity being a key modifiable factor
- Regular walking causes hippocampal growth and improved memory function in older adults over 1-2 years
- Walking produces BDNF (brain-derived neurotrophic factor) and myokines that strengthen muscles and brain resilience
- Exercise is as effective for mild to moderate depression as drug therapy or cognitive behavioral therapy
- Walking before meals blunts appetite, and walking after meals prevents blood sugar spikes
Key Moments
Why brains exist for movement
Neuroscientist Shane O'Mara explains that brains evolved specifically for movement, using the analogy of a bicycle left unused in a shed. Without regular movement, insidious changes make you more prone to depression, anxiety, and less open to experience.
"If you ever ask yourself the question, why do I have a brain? Why do you have a brain? Why do trees and plants not have a brain? Well, there's a signal difference between trees and plants and ourselves."
7,500 steps reduces all-cause mortality 30-70%
Multiple studies using activity monitors show that hitting above 7,500 steps per day dramatically reduces all-cause mortality by 30-70%, yet Western societies average only 4,500-5,000 steps.
"if you're hitting somewhere above five, above seven and a half thousand steps a day, your all-cause mortality drops, depending on the study you look at, between, let's say, 30 and about 70%."
Walking protects against brain aging and dementia
Regular walking causes hippocampal growth and improved memory in older adults, while sedentary individuals show decline. Physical inactivity is cited by the Lancet Commission as a key modifiable risk factor, with 40% of dementia cases being preventable through behavioral changes.
"dementia is not an inevitable feature of aging, and it shouldn't be thought of as an inevitable feature of aging. It's something that you can change the likelihood of happening by changing your behavior."
Walking as effective as drugs for treating depression
Recent research by Brendan Stubbs shows that exercise, including walking as the most accessible form, is as effective for moderate to mild depression as drug therapy or cognitive behavioral therapy.
"exercise is as effective for moderate to mild depression as drug therapy or cognitive behavior therapy."
Creative walking and the philosopher's tradition
O'Mara recounts how great thinkers from Kant to Darwin to Hamilton used walking as a creative tool. Mathematician William Rowan Hamilton solved his famous quaternion equation while walking 15 kilometers from the observatory to his academy.
"you could set the clock in Regensburg by Immanuel Kant, the philosopher, because he would be out at 3 p.m. Every day, rain, hail, or shine, he would go for a walk."
