This is an excerpt from Physical Activity and Obesity-2nd Edition by Claude Bouchard & Peter T. Katzmarzyk.
Built Environments and Physical Activity in Adults
There is consistent evidence that adults who live in walkable communities walk and cycle more for transportation, and have higher levels of total physical activity, than those who live in low-walkable suburban areas (3). Differences between neighborhood types of 30 to 60 min per week of physical activity have been documented with both self-reports and objective measures such as accelerometers (4). The evidence was sufficient for the Centers for Disease Control and Prevention's Guide to Community Preventive Services to classify community-scale land-use changes as effective physical activity interventions (4). Cervero and Kockelman (5) introduced the “3 D” principles of designing communities that support active transportation: residential density, land-use diversity, and pedestrian-oriented designs.
Adults who live near parks and other recreation facilities generally do more recreational and total physical activity. This association has been documented in numerous studies, but due to the wide variety of methods used, it is not possible to quantify the effects. The aesthetics of recreation facilities and communities in general have been linked with physical activity (3, 4, 6). See table 22.1 for a summary of environmental attribute associations with active transportation and recreation. Other built-environment characteristics have not been studied enough or have yielded inconsistent results, including sidewalk presence and quality, other road characteristics, availability of parking, and hills.
Just a few studies of built environments have been reported for adults aged 65 years or greater. The results generally confirm that the physical activity associations with walkable community designs and proximity of recreation facilities generalize to older adults (6).
Built Environments and Physical Activity in Youth
Connections between built environments and physical activity have been documented for children and adolescents. Living in proximity to parks and other recreation facilities, as well as high aesthetic qualities, has been associated with higher physical activity among youth (6). This can be interpreted as suggesting that children need suitable places to play near their homes. Adolescents living in walkable neighborhoods are usually found to be more active than their suburban counterparts (6). More young people walk or cycle to school when they live in walkable neighborhoods (7). However, children may use cul-de-sacs as play areas because traffic is low. Thus, suburban road networks with low connectivity may simultaneously reduce walking to school and facilitate active recreation among youth (6).
For youth, there is better evidence that sidewalks are associated with high physical activity levels (6). School grounds designed for a variety of activity opportunities may stimulate more activity during free time, such as after lunch (8). Young people generally seem to benefit from the same built-environment factors as adults, but there are additional settings (e.g., schools) and activity behaviors (e.g., walking and cycling to school) that must be considered for youth.
Causal Role of Built Environments
Most of the studies on built environments and physical activity are cross-sectional, and they have been criticized because of the possibility that people who like physical activity move to walkable neighborhoods with parks. Several studies show there is some selection into activity-friendly communities, and there may not be enough such communities to meet the demand (9). However, it does not appear that self-selection can explain all the findings because, consistent with ecological models, both psychological and environmental factors seem to operate. Auto enthusiasts who lived in walkable neighborhoods did not walk more, but living in suburban neighborhoods seemed to suppress physical activity among walking enthusiasts (9).
A major reason for the reliance on cross-sectional studies is that it is not possible to conduct a randomized trial in which people are assigned to live in different neighborhoods. However, there are several quasi-experimental evaluations of built-environment changes, though most are on a small scale. Building new trails usually increased trail use, especially when the trails were located in densely populated areas; introducing protected cycling lanes promoted cycling in Europe; changing road designs to slow traffic led to increased walking and cycling (10); and painting school playgrounds to stimulate active games led to long-term physical activity increases (11). These studies support a tentative conclusion that built environments can be causal influences on physical activity. However, these few studies are not sufficient to quantify the effects of built-environment changes.
Strengths and Weaknesses
Several aspects of this literature generate confidence in the results. The key findings about walkable neighborhoods, proximity of recreation facilities, and aesthetics have been replicated in numerous studies that differ in study designs, locations, and population characteristics. Many studies have used objective measures of built environments, physical activity, or both, so the literature is not dependent on only self-report measures. Transdisciplinary collaborations are producing innovations in models, measures, and analyses.
It is not well understood how built environment–physical activity associations may generalize to groups at high risk for physical inactivity, obesity, or chronic diseases. In some studies, low-income or racial-ethnic minority subgroups have not demonstrated the same associations as affluent or majority samples; but in other studies, racial-ethnic minority groups seemed to derive more benefit from activity-friendly environments (10).
Studies of built environments can be translated directly into policy recommendations that can be implemented by planning, transportation, recreation, and education agencies of government, along with recommendations for changed practices by architects, builders, landscape designers, and other private sector groups. However, the research has not been as influential as it could be. Studying broad variables like walkability, proximity to parks, and sidewalks does not provide sufficient guidance to tell designers and policy makers how to create optimal activity-friendly environments.
Since the turn of the 21st century, research on the built environment has become a recognized field, and consensus is rapidly developing about what kinds of built-environment changes are needed to improve physical activity in whole populations. Current research priorities are to (a) understand the built-environment characteristics that are most important for diverse population subgroups; (b) identify more specific built-environment supports for physical activity that can inform the design of optimal activity-friendly environments; (c) conduct prospective and quasi-experimental studies to improve the rigor of evidence; (d) improve understanding of how social environments (e.g., culture, social norms, media, crime) and built environments interact to influence physical activity; and (e) conduct economic and health impact assessment studies to enhance the relevance of built-environment studies for policy makers.
In a short time, the field of built-environment and physical activity research has expanded the search for solutions beyond educating the individual to a focus on environment and policy change. Researchers from many fields are using their professional relationships with practitioners to change practices, and investigators are communicating findings to policy makers in many sectors. If these efforts are successful, the groundwork will be laid for long-lasting improvements in physical activity.