Obesity and the American Way

I originally wrote this paper in the fall of 2003, on the heels of a widely publicized study that linked – with statistical significance – prevalence of overweight and obesity with the density of one’s built environment (Ewing et al 2003; McCann and Ewing 2003). Since that time, other researchers (Frank et al 2004; Lopez 2004; Saelens et al 2003b) have presented their own findings on this emerging topic. The following paper is an updated form of my original work, adapted to include a synthesis of recent academic literature on overweight, obesity, and physical activity (as it pertains to urban planning) and a streamlined set of recommendations for future research as well as implementable goals geared towards achieving a built environment conducive to increased physical activity. Statistical analysis has also been added.

“The American way of life is not negotiable”
-George H. W. Bush at the Earth Summit on the Environment, Rio de Janeiro 1992

In an October 2003 article for Orion Magazine Online, author James Howard Kunstler sideswiped the American public referring to them as “crypto-human land whales waddling down the aisles of [the] local supermarket in search of Nabisco Snack-WellsâÂ?¦ and other fraudulent inducements to ‘diet’ by overindulgence in ‘low-fat’ carbohydrate-laden treats.” Kunstler trashes the car culture that defines America, labeling our cities “hollowed out ruins,” lamenting the fact that “our towns have committed ritualized suicide in thrall to the WalMart God,” and calling our predominant way of life in suburbia “isolatingâÂ?¦ and neurologically punishing, and from which every last human quality unrelated to shopping convenienceâÂ?¦ has been expunged.” After citing the numbers, Kunstler connects the current epidemics of obesity and depression to the nation’s predominant spatial arrangement, car-dependent suburban sprawl. Despite the biting prose, when it comes to the physical condition of Americans, Kunstler is hardly hyperbolic.

Obesity and Overweight

The National Institutes of Health (NIH) (1998), and hence the Centers for Disease Control and Prevention (CDC), defines overweight as body weight in excess of a predetermined benchmark for desirable weight, in relation to height. Obesity refers to extremely large amounts of body fat relative to lean body mass. According to the National Health and Nutrition Examination Surveys (NHANES) from 1999-2000 and 2001-2002, 65.1% of adults, twenty years of age and older, were overweight or obese, 30.4% were obese, and 4.9% were extremely obese (Hedley et al 2004). Among children and adolescents, ages six to nineteen, 31.0% were either overweight or at risk for being overweight, while 16.0% were overweight (Hedley et al 2004).

The consequences of what the CDC often refers to as “the obesity epidemic” are staggering. Obesity accounts for the deaths of approximately 280,000 U.S. adults per year (Allison et al 1999). Mokdad et al (2003) reported significant associations between overweight and obesity and numerous diseases, including diabetes, high blood pressure, high cholesterol, asthma, and arthritis. Annual U.S. healthcare expenditures related to obesity morbidity totaled $92.6 billion in 1998 (Finkelstein et al 2003). And recent studies comparing healthcare costs between obese and nonobese patients revealed that obese patients had more hospitalizations, prescription drugs, and outpatient visits, making them considerably more expensive to service than the nonobese participants (Raebel et al 2004; Wee et al 2005). It should come as no surprise that obesity and overweight has made the shift from a private, individual problem to one of public concern.

The Relationship between Urban Form, Auto Use, and Obesity and Overweight

It has become common knowledge that physical inactivity puts one at greater risk of being overweight or obese. Many blame environmental factors for lack of physical activity and an increasingly sedentary American lifestyle (Berrigan and Troiano 2002; Brownson et al 2001; Giles-Corti and Donovan 2002; Handy et al 2002; Humpel et al 2002; Jackson 2003; Kreyling and Ketcham 2001). In a multidisciplinary review of literature from the fields of public health, urban planning, and urban design, Frank and Engelke (2001) conclude that in order to improve public health, physical activity must increase. Planners, they contend, can help achieve this through construction of a built environment conducive to transport options other than the automobile. An abundance of research shows that urban form, often measured in terms of density and land use mix, dictates travel behavior. Specifically, mixed-use environments produce higher rates of walking and biking and less driving than their low-density, sprawling counterparts (see, e.g., Cervero and Gorham 1995; Holtzclaw 1994; Saelens et al 2003a).

San Francisco supports the hypothesis that density drives rates of auto use and ownership. In an examination of 2000 U.S. Census data for San Francisco, I found significant correlations between population density and the percentage of residents utilizing a car (driving alone or carpooling) for their work commute (Pearson r = -.631, p < .001) as well as the percentage of households that have no vehicles available (Pearson r = .707, p < .001). Population density is also significantly correlated with the percentage of people commuting to work using options other than the private auto or carpool, i.e. public transportation, walking, bicycle, etc. (Pearson r = .648, p < .001). When controlling for poverty status, the relationship between density and auto use/ownership held. For every increase of 1,000 people in population density, the number of people utilizing a car for the work commute drops by one-half of one percent (p < .001). Similar outcomes occurred when controlling for median household income as well as when using the percentage of households with no vehicles available as the dependent variable in a multiple regression analysis (for all regression results, see Table 1).

The notion that this association between urban form, transport behavior, and physical inactivity leads to obesity and overweight has been a source of speculation in countless academic articles for years. Researchers have only recently substantiated the link with hard numbers. The following section reviews that literature.

A Body of Evidence

Ewing et al’s (2003) study was the first to statistically associate urban form with the obesity and overweight epidemic. It was also the first study of its type to saturate the mainstream media, making its way onto the front page of countless newspapers and to the top spot of many nightly newscasts over the course of several days in the summer of 2003. The widespread reporting of this scholarly finding led to numerous misinterpretations and overblown accounts by sensationalist news outlets. Case in point, an August 28, 2003 Reuters’ story bearing the headline: Urban Sprawl Makes Americans Fat, Study Finds.
What Ewing et al actually did find differs substantially from what much of the popular media reported. In their words, “urban form could be significantly associated with some forms of physical activity and with some health outcomes” (Ewing et al 2003, 54; italics added). Using data from the 1998, 1999, and 2000 Behavioral Risk Factor Surveillance System (BRFSS) surveys, Ewing et al employed metropolitan and county-level sprawl indexes as independent variables against outcome variables, such as BMI, obesity, minutes walked, and hypertension. Ewing et al found significant associations between all four dependent variables mentioned and the county sprawl index, while at the metro level, only minutes walked was significantly associated.

Lopez (2004), utilizing BRFSS data, corroborates Ewing et al’s findings. According to Lopez, as urban sprawl increases so does overweight and to a larger degree, obesity.

At the same time as providing fuel for smart growth advocates and the New Urbanists, Ewing et al added much needed statistical support to the hypothesis that the built environment impacts health. Frank et al (2004) followed with a study that did not rely on aggregate data from BRFSS; rather they were able to conduct research through a travel survey in the Atlanta, Georgia area with 10,878 participants. Obesity was the dependent variable with several sociodemographic, physical activity, and built environment measures serving as independent variables. In the end, Frank et al found that the likelihood of obesity increased by 6% for each additional hour spent in a car per day; obesity likelihood decreased by 4.8% with each additional kilometer walked per day; and for every quartile increase in land-use mix, likelihood of obesity fell by 12.2%.

Saelens et al (2003b) compared two communities in San Diego, one defined as a “high-walkability neighborhood,” the other a “low-walkability neighborhood.” This study combined the use of an accelerometer with the self reporting of physical activity performed, height, and weight. Participant perception of their built environment provided measures for environmental characteristics, including residential density, street connectivity, and aesthetics. Sample size was 107 (n=54, high-walkability; n=53, low-walkability). Results support the hypothesis that urban form influences health, specifically obesity, as more low-walkability residents met overweight criteria than high-walkability residents. 60% of low-walkability residents were overweight, while 35% in the high-walkability neighborhood were. On average, those residing in the low-walkability neighborhood had a higher BMI than that of high-walkability residents, but this comparison stopped just short of being statically significant (p=.051).

While Sturm and Cohen (2004) did not measure urban form against overweight and obesity, their work still warrants a mention in this section. Sturm and Cohen employed Ewing et al’s (2003) sprawl index against outcome variables, such as self-reported medical conditions and mental health disorders. They discovered no association between sprawl and mental health, but an increase in sprawl did accompany an increase in chronic medical problems.

Researchers have identified a possible pathway to weight-related ill health: low density � auto use � BMI/obesity � chronic health ailments. Table 2, utilizing the Bay Area in California as a representative example, illustrates the front end of this contention.

Promoting Active Daily Living

In response to the obesity epidemic, the Centers for Disease Control and Prevention (CDC) encourage development of a pedestrian and bike-friendly built environment through its Active Community Environments Initiative (ACES). ACES looks to increase physical activity, and thereby enhance the public health, by promoting walking and cycling as opposed to driving (Centers for Disease Control and Prevention 2003). As this paper suggests, a caucus is emerging that supports strategies such as those backed by the CDC to combat sedentary living and the resultant health concerns. But in order for real change to occur, the will to act must spread from a select group of academics, public health officials, and interest groups such as Smart Growth America (a national consortium of 100 advocacy organizations committed to promoting compact, mixed-use development to foster walking and biking) to a broader coalition of policy makers. Indeed, a shift in national attitude away from the prevailing ethos of car culture is imperative.

The growing discussion regarding the instability of world oil markets and the eventual end of the so-called era of cheap oil offers a golden opportunity (Deffeyes 2003; Goodstein 2004; Heinberg 2003; Roberts 2004). Whereas most of the talk emanating from Washington on the subject revolves around the promise of alternative fuels such as hydrogen, substantial dialogue, focusing on the reduction of driving, must commence. If indeed sedentary living and excessive driving is a primary contributor to obesity and overweight (and this epidemic is on a similar trajectory as a global oil crisis), the prospect of changing American lifestyles heads off numerous painstaking consequences of the status quo. This approach centers on what is an unlikely national policy of putting pedestrians, cyclists, and public transportation first, a strategy that could – in theory – lessen oil dependence at the same time as increasing physical activity and presumably improving public health. I will focus on cycling as transportation and exercise.

Pucher (1997) offers inspiration in a study of German cities (see Table 3). Despite perceived philosophical and spatial differences between Europe and the United States, a goal to increase walking and cycling in America is not unrealistic. Germany, for example, has the second highest level of car ownership in the world (behind the United States), and has suburbanized substantially. Pucher debunks the contention that lengthy travel distances in America act as a barrier to walking and cycling. 40% of all urban trips in the United States are two miles or less, and 28% of all trips are one mile or less making the bicycle a viable option (Pucher 1997). Public policy and the national mindset are the true obstacles.

Retrofitting existing roadways to provide safe passage for cyclists and reduce the automobile’s carte blanche remains an implementable ambition, even in low-density environments. Pucher offers suggestions from Germany:

� Fahrradstrassen (bicycle street): special bicycle streets which permit auto traffic but give bicyclists strict priority in right-of-way over the entire breadth of the street.

� Fahrradschleusen (bicycle way): special lanes at intersections that allow bicyclists to pass waiting cars and proceed directly to the front. Cars stop at a considerable distance from the light as bicycles fill up the roadway between the intersection and the car stop line; bicyclists also enjoy an advance green light at such intersections (Pucher 1997).

The city of San Francisco provides fine domestic examples of how planning decisions can make otherwise hostile environs friendlier to potential and present cyclists.

Thanks in large part to persistent activism and the monthly Critical Mass bike rides, miles of bike lanes have been striped throughout San Francisco since the early 90’s; hundreds of bike racks have popped up in the city; bike commuters are on the rise; and bike-related injuries are down (Gajda and Markowitz 2005). While no direct causal link has been established, bike lanes are thought to be a major contributor to the fact that 1 in 25 San Francisco adults commute regularly by bicycle (San Francisco Bicycle Coalition 2003). After the city striped bike lanes on Valencia Street, bicycling increased on that street by 144 percent. In fact, cyclists now account for 16% of vehicles during rush hour on Valencia (Department of Parking and Traffic 2000).

While traditional bike lanes are an asset, planners must consider going beyond the typical solid white line that separates the bike lane from motor vehicle lanes. Coupled with special advantages (Fahrradstrassen and Fahrradschleusen), bikes lanes, painted a color distinct from the street with strong protective buffers between the cyclist and auto traffic, should be encouraged. Thanks to such design specifications, motorists may view bike lanes as more than an impediment to right turns. Special delineation of bike lanes may prompt car drivers to give them the same respect as they do sidewalks. It is not too often that one sees cars driven or parked on city sidewalks, as is frequently the case with bike lanes.

Pollard (2003) suggests wholesale changes in planning to combat sedentary lifestyles. He calls for an overhaul of current zoning regulations, many of which prohibit mixed-use land development, thereby rendering walking and cycling impractical and dangerous in such environments. He also suggests that governments discourage driving by removing parking provisions and altering the design of roads to accommodate pedestrians and cyclists as opposed to high-speed automobile traffic (Pollard 2003).

Alterations to the built environment and adjustments to the flow of auto traffic in the form of bikeways, bike streets, bike lanes, advance green lights for bikes, direct routing, and other modifications make cycling and walking a more attractive option than it would be otherwise. Implementation is the challenge, as most local governments operate within a system where driving is a way of life.

Recommendations for Future Research

Overweight and obesity is no longer an individual concern. Its economic impact in terms of health care costs, its connection to other life-threatening and life-altering diseases, and the rapid growth of overweight and obesity in children has elevated its status to epidemic levels. Overweight and obesity is raising substantial public concern. A convincing body of research implicates car-dependent environments and their association with physical inactivity as a primary contributor to overweight and obesity. A popular remedy calls for construction of more compact urban and suburban settings that mix land uses in an effort to increase rates of walking and cycling for both utilitarian travel and leisure time activity. Such a goal requires cooperation between urban planners, urban designers, architects, and developers, the public health sector, government entities, as well as advocacy and citizens groups.

In order for this cohesion to occur, further research is required on the subject. Researchers must replicate the types of studies cited in this paper across the country in various settings, taking into account variables that might be working in concert with, or separate from, urban form to bring about such alarming rates of overweight and obesity. While the hypothesis that urban form drives levels of physical activity and physical activity drives physical well-being is gaining credibility, this issue is hardly one-dimensional. How much of a role do age, education, socioeconomic status, and other neighborhood factors (such as availability of healthy food choices) play alongside urban form in contributing to the epidemic? For instance, what impact does a concentration of fast food restaurants have on one’s weight? In San Francisco’s high-density Mission District, the population is diverse in terms of ethnicity and financial resources. Do residents with less money eat at the inexpensive fast food chains, concentrated at busy corners, while those with means select healthier choices? And if so, what are the age, race, and health differences between the two groups living in the same built environment? This query, tweaked for local conditions, can be applied anywhere in America.

Saelens and et al’s (2003b) comparison of what they defined as “high-walkability” and “low-walkability” neighborhood warrants further efforts. Drawing distinctions between exurban, suburban, close-in suburban, and varying types of city neighborhoods (i.e. the high-density Nob Hill or North Beach districts of San Francisco versus the relatively low-density Sunset or Richmond districts) offers researchers the ability to hone in on exactly what role density and proximity to work, school, and services has on one’s weight and general physical well-being.

Of course, a limitation of the recommendations made in this paper is that the ideas focus on San Francisco and Germany. I would argue that initiatives and design specifications enacted in these places can be duplicated, even in suburban settings, but further study on best practices for fostering walking and cycling (and less driving) from divergent locales is necessary.
Hard research on obesity and overweight in relation to urban planning concerns is in its infancy, but the epidemic is not. Intense scrutiny of our built environment’s association with public health is required if urban planning hopes to play a role in curbing what might just become the number one cause of preventable death in the United States before the decade is out.

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