Background and Purpose
Smart growth urban planning strategies (e.g., preservation of open space, integration of mixed land uses, establishment of compact building design, creation of walkable neighborhoods) may increase physical activity and lower obesity risk. It is thought that smart growth communities offer greater opportunities to be physically active in settings that are safer, have lower traffic exposure, and are more aesthetically pleasing (e.g., greater greenness, vegetation, shade). However, it is unknown whether residents of smart growth communities actually perform physical activity in safer and more aesthetically pleasing settings, and how performing physical activity in safe and aesthetically pleasing settings is related to overall physical activity levels and obesity. This limitation, known as the uncertain geographic context problem (UGCoP), is a growing concern in research on the built environment and physical activity, It is characterized by a lack of clarity about (1) the specific context or setting that has a direct influence on health-related behaviors; and (2) the timing and duration of individuals’ actual exposures to these contextual influences. To address these concerns, the present study used a real-time data capture strategy, Ecological Momentary Assessment (EMA), to measure where physical activity occurs and perceptions of those settings.

Objectives
This study used EMA with electronic surveys delivered through mobile phones to determine whether perceived safety, traffic, and aesthetics of settings, where physically activity actually occurred, mediate the effects of living in a smart growth community on physical activity, body mass index (BMI), and waist circumference in adults.

Methods
Research used a two-group quasi-experimental (“natural experiment”) design. Participants included 58 adults who had recently moved to a smart growth community in Southern California and a demographically-matched set of 59 adults living in nearby urban-sprawling comparison communities. The groups were comparable in age (M = 40.7 years, SD = 9.6), gender, (72% female), ethnicity (31% Hispanic), and income (27% < $40,000/yr). Individuals participated in eight days of EMA via mobile phones, with eight random EMA surveys per day between 6:30am and 10:00pm. EMA items measured current activity (e.g., eating, watching TV, physical activity/sports), physical context (e.g., home [indoors], home [outdoors], outdoors [not at home], work), and perceptions of that context if outdoors (i.e., safety, traffic, greenness/vegetation, shade, litter). Adults wore an Actigraph GT2M accelerometer to assess daily moderate-to-vigorous physical activity (MVPA). Height, weight and waist circumference were measured by research staff. Person-level average scores for perceived safety, traffic, greenness/vegetation, shade, and litter were calculated across EMA prompts when physical activity was reported in outdoor contexts. Direct and indirect effects of living in a smart growth community on perceptions of physical activity contexts, MVPA, BMI, and waist circumference were tested using linear regressions and bootstrapping in the SOBEL macro for SPSS.

Results
Residents of the smart growth community reported greater safety in outdoor physical activity settings than the comparison group (ß = .38, p = .017). Also, greater perceived safety of outdoor physical activity settings was negatively associated with lower BMI (ß = -.266, p = .050) and waist circumference (ß = -.298, p = .033), and positively related to daily MVPA (ß = .239, p = .079). The indirect effect of living in a smart growth community (through perceived safety of physical activity settings) was statistically significant for waist circumference (estimate = -3.39, 95% CI = -6.89 to -0.48) but not for BMI or MVPA. Perceptions of greenness, shade, traffic, and litter did not differ between individuals living in the smart growth versus control communities (p’s > .05). However, greater perceived greenness of outdoor physical activity contexts was associated with lower BMI (ß = -.297, p = .028), and greater perceived shade protection of outdoor physical activity contexts was associated with higher daily MVPA (ß = .274, p = .043) regardless of group.

Conclusions
Using a novel, real-time data collection strategy, this study found that greater perceived safety of physically activity settings may partially account for lower waist circumference among smart growth residents as compared with individuals living in urban sprawling comparison communities. Results suggest that smart growth planning may not influence perceived greenness, shade, traffic, and litter of outdoor physical activity contexts. However, these findings need to be replicated in other smart growth communities. Among all participants, regardless of community residency, those who performed physical activity in contexts with greater perceived shade from the sun were more physically active overall. Also, individuals who performed physical activity in contexts with greater perceived greenness had lower BMI’s on average. These findings suggest that performing activity in outdoor settings with specific features such as greater shade, greenness, and safety may offer conditions that promote more sustained, intense and/or frequent activity and lower obesity risk.

Implications for Practice and Policy
Designing communities according to smart growth urban planning principles may create subjectively safer places to be physically active, leading to lower obesity risk.

Support / Funding Source
American Cancer Society (118283-MRSGT-10-012-01-CPPB) and the National Cancer Institute (R01CA123243).