Influence of the retail food environment around schools on obesity-related outcomes: a systematic review

Abstract

BackgroundSoaring childhood obesity rates have led to questions about the influence of obesogenic environments on children's health. Public health interventions that target the retail food environment around schools have been proposed, but whether these interventions are evidence based is unclear. MethodsWe examined associations between the retail food environment near schools and food purchasing, consumption, and bodyweight of students. We catalogued and critiqued the methods and results of studies analysing these associations and sought to assess the quality of evidence within the publications. We undertook a keyword search of several databases and sources of grey literature, including Medline, Embase, Web of Science, and the Cochrane Public Health Group specialised register. Inclusion criteria required studies to be published in a peer-reviewed journal between January, 1981, and October, 2012, provide at least one measurement of food retailing surrounding schools, and include outcome data for school children aged 5–18 years. Two researchers independently reviewed papers and blindly assessed the quality of the study using a modified checklist that covered study design and reporting. Methodological heterogeneity precluded meta-analysis, so we used a semiquantitative method in which we categorised papers according to their outcomes and identified whether or not the outcome was significantly (p<0·05) associated with the density or proximity of food outlets near schools. Findings21 studies met our inclusion criteria. All followed a cross-sectional study design. 19 described the food environment with geographical-system-information-based measures (eg, the density or proximity of food outlets within a buffer zone around the school) and two characterised the food environment using qualitative data. Outcome measures varied considerably. Only one study examined effects on food purchasing behaviour. Far more common were studies examining effects on the consumption of fruit and vegetables and of foods high in fat, sugar, or salt, or the effects on bodyweight. The one study that examined the associations between food outlets and food purchases showed a significant correlation between the proximity of fast food outlets and the number of fast food purchases. Five papers assessed associations between food outlets around schools and the consumption of fruits and vegetables. 34 relations were assessed, half of which showed a positive correlation. Only one of these results was significant (p<0·05). Five papers assessed associations between the food environment and consumption of foods high in fat, sugar, or salt. 41 assessments were reported, 21 of which showed that the number of food outlets near schools was associated with increased consumption of these foods. None of the results were significant. 14 papers examined associations between the food environment and increased bodyweight. 57 assessments were reported, 33 of which were positive and the remainder negative. Among the positive associations, 15 were significant. Among the 24 negative associations, seven were significant. InterpretationThis review of the scientific literature found very little evidence for an effect of the retail food environment surrounding schools on food purchases and consumption patterns, but some evidence of an effect on bodyweight. Given the general lack of evidence for association with the mediating variables of food purchasing and food consumption, and the observational nature of the studies included in this review, it is possible that this finding is a result of residual confounding. The methods for the studies varied, but many contained worrying limitations; for example, most studies measured exposure at the level of the school and only one study considered children's actual journeys through the food environment. Better studies are required to inform effective public health policies. FundingBritish Heart Foundation, NHS Berkshire.