The study team assessed the food environments of 24 upper secondary schools using a validated food retail environment assessment protocol. Their audit covered both the school canteens themselves and 100 food retail outlets operating in the immediate vicinity of the schools, capturing a total of 124 retail settings. This dual approach matters because adolescents do not eat exclusively at school; they move fluidly between the canteen counter at morning break and the corner shop on the way home. By measuring both settings with the same instrument, the researchers could ask whether the canteen, the surrounding shops, or some combination of the two is the more meaningful driver of dietary behavior. The audit recorded what foods were available, how much shelf space each category occupied, how products were priced relative to one another, and what kinds of advertisements appeared on walls, counters, and windows.

The marketing findings were among the most dramatic in the study. The researchers identified 530 food advertisements across the audited settings, 499 of them in the surrounding food retail outlets and 31 in the school canteens. When each advertisement was evaluated against the World Health Organization’s Eastern Mediterranean Region Nutrient Profile model, known as the WHO-EMR-P, a staggering 90.8 percent of advertisements in the food retail outlets and a full 100 percent of those inside the canteens were classified as non-permissible. In other words, essentially every food advertisement a student in Shiraz encounters in and around school promotes a product that fails the regional WHO standard for marketing to children. For a population of minors, the sheer saturation of non-permissible marketing represents a policy failure that no single school can address alone, since the overwhelming majority of the advertising burden sits just outside the school walls in privately operated shops.

To connect these environmental measurements to actual behavior, the researchers assessed dietary intake in 656 students using a validated 90-item Food Frequency Questionnaire, and they collected anthropometric measurements, including indicators of body composition, at the same time. Because the students were minors, written informed consent was obtained from their parents before enrollment, and the study was approved by the Ethics Committee of Shiraz University of Medical Sciences. The analytical strategy relied on mixed-effects models, a statistical framework well suited to this kind of nested data, in which individual students are clustered within schools. This approach allowed the researchers to estimate the association between each school-level food environment characteristic and each student’s intake while accounting for the fact that students in the same school share a common environment and are therefore not fully independent observations.

The headline result is that availability emerged as the most consistent predictor of what students ate. Greater availability of a given food category was associated with higher intake of that same category across a remarkably broad range of products. The effect was statistically significant for healthy dairy products, with a coefficient of 3.291 and a p-value of 0.008, and it held for unhealthy dairy products as well, with a coefficient of 6.737 and a p-value of 0.042. Unhealthy cakes and biscuits showed a coefficient of 1.428 with a p-value of 0.002, one of the strongest associations in the dataset. Beverages, chips and puffs, and sweets each also displayed significant positive associations, with coefficients of 0.403, 0.090, and 0.175 respectively. The pattern is intuitive but consequential: when a food category commands more shelf space in the canteen or the shops nearby, students consume more of it, whether the category is one that nutritionists would applaud or one they would warn against.

Just as notable is what did not predict intake. Food prices, despite the considerable attention that pricing interventions such as sugar taxes and subsidy schemes receive in the public health literature, were not significantly associated with dietary intake in this sample. The researchers did observe that price differences varied across food groups, with unhealthy products being more expensive in some categories and less expensive in others, suggesting that the price landscape around Shiraz schools is heterogeneous rather than uniformly favoring cheap junk food. Yet that heterogeneity did not translate into measurable differences in what students reported eating. Similarly, advertising density showed a more limited footprint than availability, reaching statistical significance only for healthy ready-to-eat foods, with a coefficient of 0.711 and a p-value of 0.049, and for simple sugars, with a coefficient of 3.054 and a p-value of 0.015. The association with simple sugars is consistent with the concern that heavy marketing of sugary products drives consumption, but the overall advertising signal was far weaker than the availability signal.

Perhaps the most sobering finding for anyone hoping that a single environmental lever could transform adolescent health is that no school-level food environment indicator was associated with overall nutritional intake or with anthropometric outcomes. Body measurements, in other words, did not shift in detectable ways with the characteristics of the food environment that the study measured. This null result should be interpreted carefully rather than dismissively. Cross-sectional designs capture a single moment in time, and anthropometric outcomes such as body mass index reflect years of accumulated energy balance, genetic factors, physical activity, household food environments, and socioeconomic circumstances that a school-based audit cannot disentangle. A student’s weight at age sixteen is the product of a lifetime of exposures, most of which occurred long before the research team arrived with their measurement protocol. The absence of an anthropometric association does not mean the food environment is irrelevant to obesity; it means that the pathway from shelf space to body size is long, buffered, and difficult to detect in a snapshot.

The technical architecture of the study deserves attention because it illustrates the methodological machinery behind modern food environment research. The distinction between school canteens and food retail outlets as separate strata, the use of shelf space as a continuous measure of availability, the application of the WHO-EMR-P nutrient profile as an external, standardized benchmark for classifying advertisements as permissible or non-permissible, and the use of mixed-effects regression with appropriate attention to multiple testing all reflect a maturing field that has moved beyond simply counting fast food restaurants near schools. The researchers also employed false discovery rate control, a statistical correction that reduces the risk of spurious findings when many associations are tested simultaneously, lending additional credibility to the associations that survived. The 90-item Food Frequency Questionnaire, meanwhile, allowed intake to be analyzed at the level of food groups rather than single nutrients, which is the level at which food environment interventions actually operate.

The authors conclude that school food environments in Shiraz were characterized by a predominance of unhealthy foods and widespread unhealthy food advertising, and they argue that strengthening and monitoring food environment policies in and around schools may help improve the availability and promotion of healthier options. The emphasis on monitoring is significant. A policy that restricts what a canteen may sell does nothing, on its own, about the 100 food retail outlets surrounding the schools or the 499 non-permissible advertisements displayed in them. Effective regulation of the school food environment therefore has to extend beyond the school gate, a lesson that jurisdictions from Chile to the United Kingdom have learned through mandatory front-of-pack labeling laws, zoning restrictions on fast food outlets near schools, and statutory limits on the marketing of high-fat, sugar, and salt products to children. The Shiraz data suggest that in this setting, such measures would be attacking an environment in which nearly nine out of every ten advertisements a student sees fail the regional WHO standard.

For the broader scientific conversation, the study contributes a clear hierarchy of environmental influence. Availability, measured as the physical presence and shelf space of food categories, behaved as the workhorse variable, consistently tracking with intake across healthy and unhealthy categories alike. Pricing, in this particular market context, did not. Advertising mattered for some categories but not others. None of the three levers moved the needle on body measurements in a cross-sectional frame. That hierarchy gives policymakers a practical ordering: if the goal is to change what adolescents eat today, changing what is on the shelves is the intervention with the strongest evidentiary support from this study. If the goal is to change what adolescents weigh, the evidence base remains far more complex, and school food environments are likely only one thread in a much larger fabric of determinants. The study, funded by Shiraz University of Medical Sciences and published open access, adds an important data point from a region of the world where such granular environmental audits have historically been scarce, and it underscores a simple truth that resonates far beyond Iran: adolescents eat what is put in front of them, and right now, what is put in front of them is overwhelmingly unhealthy.

Subject of Research: Associations between school food environment characteristics and adolescents' dietary intake and anthropometric outcomes

Article Title: Associations of school food environment characteristics (availability, pricing, and marketing) with adolescents’ dietary intake and anthropometric outcomes

Article References: Associations of school food environment characteristics (availability, pricing, and marketing) with adolescents’ dietary intake and anthropometric outcomes. (n.d.). https://doi.org/10.1186/s12889-026-29686-y

Image Credits: AI Generated

DOI: 10.1186/s12889-026-29686-y

Keywords: adolescent health, school food environment, dietary intake, food availability, food advertising, food pricing, school canteen, obesity, BMC Public Health, Iran, WHO nutrient profile, public health nutrition