DENVER — Quite a few of the frighteningly fit live around here. On a balmy Saturday, or for that matter a frigid winter weekday before dawn, an army of them emerges to run and bike. And in their intimidating long strides and whirring spokes, they underscore why Colorado is the least obese state in the nation.

But walking to get somewhere? Different story.

People like Gosia Kung and Dr. Andrew M. Freeman are trying to change that. In very different ways and for different reasons — she is an architect, he a cardiologist — they are trying to reincorporate physical activity into the sinews of a place that, despite its fantastic body mass index, lost touch like most American cities with the idea of walking as transportation.

Last year, Ms. Kung co-founded a nonprofit group called Walk Denver, which is trying to get the city certified as a “Walk Friendly Community.” It is also an advocate for a previously voiceless group, the ordinary walker — whispering into the ears of city planners, or nagging if need be, and preaching to the public.

It is the physical space of a city, Ms. Kung said on a recent walk through downtown, that creates a pedestrian’s view of the world. Ample sidewalks are crucial, she said, but they provide only the means of access to an environment that must then reward walkers through attractions like shopping and entertainment that cater specifically to foot traffic.