This sounds like one of the billion things correlated with having less money. https://www.citylab.com/life/2012/03/why-people-cities-walk-...
Fascinating results.
Here's a short article about his book, Scale: https://blogs.sciencemag.org/books/2017/07/11/a-physicist-pr.... He's spoken with TED too: https://www.ted.com/talks/geoffrey_west_the_surprising_math_....
Here are my podcast episodes with him, where he describes his findings: http://joshuaspodek.com/guests/geoffrey-west.
(I'm a former physicist too who walks fast at 48.)