A recent research found that people lived in New York city have a significantly lower body mass index (BMI) compare people who live in suburb area of New York.
The research suggested that people in NYC live close to commercial area. Instead of driving, they walk to retail store and restaurant. Also, they are more likely to use public transit that require more walking than driving.
I am not sure if more walking is the only reason that most New Yorker has lower BMI. I believe higher education and income also play a role.
The full article
http://www.livescience.com/humanbiology/070220_city_skinny.html
