The walking and the stairs. So many stairs. I don't know many friends who live in buildings with elevators, especially in the outer boroughs. We live in a four-story walk-up in Brooklyn, have stairs in our duplex to go to the second story/loft, and walk up and down subway stairs on a daily basis. So all those stairs plus generally walking everywhere around the city equals a lot more exercise on a daily basis than the average person (is my guess).

It's night and day versus growing up in Austin, where I drove everywhere, rarely used stairs, and walking consisted of taking out the garbage to the curb.

I gained about 15 lb relocating out of NYC & working from home. Didn't change diet - I lost the ~30 minutes of NYC-fast-walking I did every day (to/from subway on each end).

Now, whenever I am out visiting clients etc. in the city I peg my Apple Watch's fitness meter - most days I barely get anywhere. Was eye opening - I now start my day with 45-60 minutes of moderate cycling and I've dropped back to my pre-work-from-home weight and noticeably/significantly raised my energy level.

I now acutely understand the plight facing our suburban citizens.

I'd expect that to apply equally to wealthier people too, but the inter-city gap disappears at higher income levels. Wealthy New Yorkers also walk a lot more than wealthy people in other countries.

New Yorkers definitely walk a lot more, but I don't think that explains the full effect.

Absolutely this. Lots of people I know who've lost tons of weight started attempting to eat better and then walked an hour or more a day. I started walking every day and dropped my resting pulse into the 50's, and lowered my blood pressure from barely normal, to near athletic.

All that walking is just awesome for people's health. And most people in the US don't get much exercise.

100% - when I go home to NYC average daily walking is 5-8 miles vs. 1-3 in Houston...an extra 5+ miles a day in walking adds up...

I would put a lot of money on this as well.

I came here to say this. The health benefits for the heart and lungs of "active walking" are well established and anecdotally, people in NYC just walk from place to place constantly vs. other cities. Even metros like SFO. It's even worse in places like Atlanta and Dallas where you basically have to drive from place to place.