If you have to drive to work rather than walk, if you live in a neighborhood that is not well served by restaurants, bars, and corner food stores, then your daily steps have to be planned. They don’t happen as an organic part of daily life. Most Americans who live outside the downtowns of major cities experience this: Naturally occurring walking is rare, the result of standard suburban design.

I had a chance to quantify the effect recently. I was stuck for three days in Manhattan by snow. Necessity, convenience, and the simple pleasure of walking in Manhattan (despite the muck and the slush) had me averaging 7,000 to 9,000 steps a day, as recorded by my UP band. At home in Birmingham, Alabama, where I must drive to work and where the office is within walking distance of practically nothing, I average about 2,500 steps before I head out for some focused footwork. This lack of naturally occurring exercise back home means that if a day passes in which I can’t slot steps in, I face a deficit of as much as 6,500 steps.

By sprawling our cities, we traded away part of our health for lifestyle, without even understanding what the trade-off was. It doesn’t have to be that way: Award-winning suburban towns like Louisville, Colorado—where my wife and I have a house—have mandated extravagant amounts of walking paths and open space into their designs. But that’s because of local demand: There’s a fitness ethic in the Boulder area that’s as fierce as the party ethic in New Orleans, where they have drive-through daiquiri bars.

The perfectly tuned car-centered life can probably get daily step counts below 1,000, which I suspect is also the steps goal of the three-toed sloth. The connection between exercise and obesity isn’t absolutely understood—diet seems to play a far bigger role—but eliminating naturally occurring exercise must have done us harm. One goal of community design now should be building that exercise back in at every turn.