If your kid is fat, Mark Fenton says, blame the car.

“We’ve built such an autocentric world, it’s possible to expend no calories while going about the routines of daily life,” Fenton told a Lawrence audience Monday, showing them a picture of a car rolling past a fast-food drive-through window.

That inactivity has far-reaching health consequences, he said. Too many people fail to get the 30 minutes of exercise a day recommended by federal health officials.

“We’re raising a generation of kids,” Fenton said, “who are so physically inactive that their life spans will be 2 to 5 years shorter than their parents.'”

His solution: Hit the sidewalks and start hoofing it.

Fenton, host of the PBS program “America’s Walking” and a former member of the national racewalking team, was in Lawrence for a Walkable Community Workshop sponsored by the National Center for Bicycling & Walking.

Two dozen people attended — mostly city planning and traffic officials, but also several representatives from development firms. Fenton led a “walking audit” through downtown and Old West Lawrence to get a sense of the city’s “walkability.”

He paused at a planter in the 700 block of Massachusetts that was flanked by benches, a water fountain, newspaper machines and a bike rack.

“Does this not say we’d love you to walk downtown?” he asked.

Still, he offered officials a list of options to make the city more pedestrian-friendly.

Lawrence already has some of the measures in place: speed humps, traffic circles and a “road diet” like the one that converted Connecticut Street from four lanes to two.

Other measures haven’t been tried here yet. “Chicanes” convert straight roads into winding, curvy streets that slow vehicle traffic. Reverse parking — where vehicles would back into their parking stalls — would make it easier to unload trunks and children onto sidewalks, Fenton said.

Members of the audience brainstormed their own ideas to encourage walking: a free day at the swimming pool for those who arrive on foot or bicycle; increased City Hall funding for sidewalk maintenance; and closing Massachusetts Street to vehicle traffic on Friday and Saturday nights.

City Hall already has made “pedestrian transportation” a priority. Commissioners have pressured developers to make room for sidewalks between cul-de-sacs; subdivision regulations require sidewalks in new neighborhoods; and the Traffic Safety Committee just spun off its own ad hoc subcommittee, the Pedestrian Advisory Council.

6News video: National expert wants to get Lawrence residents walking How could City Hall make Lawrence more safe and friendly for pedestrians? National Center for Bicycling & Walking America’s Walking: Resources & Links

“I think we’re pretty much into it,” Planning Director Linda Finger said. “We’re trying to bring the pieces together.”

Fenton agreed.

“Lawrence,” he said, “has the capacity to be one of the model communities.”