摘要：Objectives. We examined the association of participation in community gardening with healthy body weight. Methods. We examined body mass index (BMI) data from 198 community gardening participants in Salt Lake City, Utah, in relationship to BMI data for 3 comparison groups: neighbors, siblings, and spouses. In comparisons, we adjusted for gender, age, and the year of the BMI measurement. Results. Both women and men community gardeners had significantly lower BMIs than did their neighbors who were not in the community gardening program. The estimated BMI reductions in the multivariate analyses were −1.84 for women and −2.36 for men. We also observed significantly lower BMIs for women community gardeners compared with their sisters (−1.88) and men community gardeners compared with their brothers (−1.33). Community gardeners also had lower odds of being overweight or obese than did their otherwise similar neighbors. Conclusions. The health benefits of community gardening may go beyond enhancing the gardeners’ intake of fruits and vegetables. Community gardens may be a valuable element of land use diversity that merits consideration by public health officials who want to identify neighborhood features that promote health. There were more than 18 000 community gardens in the United States and Canada in 2011, and their numbers are growing. 1 Researchers assessing the impact of community gardening have concluded that they confer social benefits to neighborhoods 2–5 as well as nutritional, 6–11 physical activity, 9,12,13 and general health 9,13,14 benefits to participating gardeners. However, many of these studies rely on data from small numbers of gardeners 8–10,12,14 or surveys with very low cooperation rates (i.e., 8%–15%). 6,13 These methodological shortcomings have led to calls for more rigorous quantitative investigations of community gardens’ benefits. 15,16 We used unique administrative data to examine the relationship between community gardening and a previously unexamined outcome, body mass index (BMI; defined as weight in kilograms divided by the square of height in meters). We focused on BMI and the associated risk of being overweight or obese, as they are summary measures that jointly reflect caloric intake and physical activity. The decision to garden likely influences both caloric intake and physical activity. Overweight and obesity are known risk factors for numerous life-threatening health conditions, including coronary heart disease, stroke, hypertension, and type 2 diabetes. Thus, any observed relationship between gardening and the risk of being overweight or obese may also have implications for other health outcomes. Ideally, community gardening would be assessed by a random assignment of people to garden or to a control group of nongardeners. This would ensure that any differences observed between the 2 groups were a function of gardening rather than of other participant characteristics. 17 Because we did not have the ability to randomly assign people to gardening treatment and control groups, we utilized a posttest-only comparison group design to assess the impact of community gardening on BMI. 18 This quasi-experimental design had the advantage of maximizing the power of our study by relaxing the need for both pregardening and postgardening BMI observations that would be available for only a select subset of our gardeners. In addition, it allowed for the inclusion of multiple comparison groups. However, we could not make strong statements regarding causal inferences with the posttest-only comparison group because of the selection threats inherent in the study design. 18 Our treatment group consisted of community gardeners. We compared the BMIs of these gardeners to their counterparts in 3 control groups: (1) unrelated individuals who lived in the gardeners’ neighborhoods, (2) siblings of the community gardeners, and (3) the spouses of the community gardeners (i.e., comparing women [men] gardeners to the wives [husbands] of men [women] gardeners). Comparisons of gardeners with these 3 groups had the potential to provide unique insights. Unrelated individuals living in the same neighborhood share the same physical environment (e.g., opportunities for walking and other physical activities, proximity to retail food outlets) and are likely to be of similar socioeconomic status as the gardeners. Same-gender adult siblings may or may not share socioeconomic status or neighborhood residential characteristics, but they do share familial genetic predispositions for body types and they may share eating and exercise preferences that were established growing up in the same family. Finally, spouses of gardeners likely share the nutritional benefits of the produce that is harvested. They may also participate in some community gardening activities along with their partners who garden, and these activities may increase their energy expenditures. Thus, we hypothesized that we would observe the largest BMI differences between community gardeners and the unrelated individuals in their neighborhoods; that we would observe smaller differences between the community gardeners and their siblings; and that BMI differences between community gardeners and their spouses would be very small or nonexistent.
