In 2008, Mayor Mick Cornett — personal weight 217 pounds — put Oklahoma City on a diet. Numerous rankings repeatedly placed the state capital among the fattest cities in America, with obesity rates accelerating faster than in anywhere else in the country. ”This city is going on a diet” was Cornett’s challenge to his fellow citizens to join him in losing weight. Nicknamed the OKC Million because of its initial goal to shed a collective 1 million pounds (the equivalent of 100 elephants, according to a boast on the city’s Web site), the crusade to encourage a healthier, more active community attracted national media attention in the US and has been hailed for tackling a stubborn social challenge.

But Mayor Cornett and Oklahoma City did more than just lose a lot of weight. They have pushed the frontiers of public health with a less publicized but highly innovative approach to combating obesity: the Metropolitan Areas Project, a 10-year urban planning program that began in 2010. Now in its third phase, known as MAPS 3, it aims to reduce reliance on cars by increasing the city’s walkability and altering the urban environment to encourage public transit, walking and biking. MAPS 3 will add over 30 miles of sidewalk to Oklahoma City, see the expansion and increased connectivity of its trail system, add 70 acres to a redesigned downtown public park and create a rail-based streetcar system. It also includes a whitewater rafting facility and improved river race course to encourage river-sport training.

The impetus for MAPS came from a growing body of research that finds a strong link between the built environment and public health.  ”Built environment” is a term commonly used by urban planners to encompass urban design, land use and the transportation system — and health planners are increasingly interested in measuring the effect of these physical surroundings on human behaviour. Research so far suggests that factors such as building density, the mix of land use (the ratio of parks to roads, for example), the interconnectivity of travel routes and the aesthetic appeal of a neighbourhood all play a role in influencing residents’ physical activity, and by extension overall public health.

An important 2009 study out of San Diego State University found that across 11 countries, including Canada, the United States, China and Brazil, neighbourhoods designed to support physical activity by residents experienced significantly higher rates of adequate physical activity compared with those neighbourhoods with no supportive attributes. Though the importance of particular attributes varied by country, the study found that the presence of sidewalks was highly predictive of higher rates of physical activity across all 11 countries.

Now, by testing the theory that there is a relationship between a city’s built environment and its citizens’ health, Oklahoma City offers a model for a living laboratory to see if public health can be improved when a city designed to accommodate the car is altered to encourage physical activity.

The majority of North American cities were developed long before the health consequences of the built urban environment were known to city planners. Cities that were designed and then sprawled after the Second World War tended to prioritize convenience for automobile traffic and the postwar ideal of the suburban family home, rather than being tailored for health and environmental considerations.

”We had inspired our civil engineers through the years that their job was to see how fast they could get cars from one place to another,” Cornett said in an interview with the Atlantic‘s ”Cities” Web site, adding: ”Mission accomplished.” Cornett said that Oklahoma City’s sprawl meant traffic congestion was rare and real estate was big and cheap. It was also a key variable, he believes, in explaining the city’s soaring rates of obesity and diabetes.

Combatting health problems with large-scale urban construction projects such as MAPS is not without upfront costs for the city. MAPS 3 is funded entirely at the local level through a 1 percent sales tax over seven years to raise the expected cost of $777 million. Presented to voters as a package deal, the project was an all-or-nothing endeavour, and public support varied significantly across individual projects. Councilman Ed Shadid of Oklahoma City notes that $340 million of the planned investment is reserved for the building of a convention centre and fairgrounds to promote trade shows, for which public support was polled to be no higher than 7 percent. ”Nobody made an argument that the convention centre would have any impact on public health,” he says. ”It was strictly an economic development tool.” According to Shadid, the proposed investment in public transit, trails and sidewalks was what ensured that MAPS 3 passed at the polls. The portion of total dollars targeted for improving these elements of the project, however, won’t do enough, he says. ”Oklahoma City hasn’t built sidewalks in 40 years. The need is overwhelming. Though our consultants identified 250 miles of priority sidewalks throughout the city, the project is only building 35.”

There are also questions about whether MAPS will work in other cities. In Canada, where obesity does not pose a public health problem of the same intensity as in the US, cities continue to sprawl. Some have tried to counter the car-centric nature of the urban environment by taking steps to make their cities more walkable: new developments in Victoria, BC, and Barrie, Ontario, provide walking and biking trails in an effort to encourage physical activity.

But it remains far easier to build a better urban environment from scratch than to modify what already exists. ”It’s more expensive to do it the way we’re doing it,” Cornett acknowledges of his sidewalk project. And Canadian municipalities do not have the same taxing powers as their American counterparts. Oklahoma City’s tax scheme would be harder to carry out in Canada, where municipalities are not allowed to carry operating deficits or permitted to implement income or sales taxes (albeit for some rare exceptions such as a gasoline surtax). For the most part, their revenue-generating powers are limited to property taxes and user fees. These restrictions impose severe constraints on a municipality’s ability to engage in the longer-term spending commitments that a MAPS requires.

Despite the plaudits for Oklahoma City’s initiatives, Shadid and others point out that there are no health impact assessments of the MAPS initiative. ”Nor is there any prospective  study that would allow us to track the impact of these particular investments,” Shadid notes. That makes it hard to measure whether the city’s investment is reaping a healthier citizenry or is turning out to be no more than a glorified — and expensive — landscaping project. The anecdotal evidence suggests that some city, somewhere, should try to find out.