Exploring dietary patterns during school hours in Swedish adolescent student population, focusing on out-of-school eating and snacking: a repeated cross-sectional study

Abstract Background Establishing healthy dietary habits during childhood and adolescence is essential, as these patterns often persist into adulthood and influence long-term health. In Sweden, school lunches play an important role in overall nutritional intake. However, among adolescents, school lunch participation may decrease, while purchasing food from nearby retailers becomes increasingly common. This study aims to investigate dietary patterns among adolescents aged 13–19 years in Stockholm, Sweden, during school hours, focusing on school lunch participation and snacking inside and around school. Methods A repeated cross-sectional study was conducted over four years, with independent student samples recruited each year from two schools in central Stockholm, an area with high density of fast-food retailers. Data were collected in 2019–2021 and 2024 and included self-reported pictures of meals and beverages, and self-rated dietary habits. Images were collected through school-based citizen science projects using purpose-built mobile apps that recorded GPS-tagged pictures, indicating eating locations. Manual image annotations were used for nutritional assessment. Results Four hundred eighty-three participants were included, contributing 4,562 images. In total, 21% of meals and drinks were reported outside school grounds. The proportion of unhealthy meals was significantly higher outside than inside school (65% vs. 43%, χ 2 = 109.6, p < 0.001). Meals consumed inside school more often comprised components of a complete meal and contained significantly higher proportions of vegetables, red and processed meat, and fish and seafood (all p < 0.001) compared with meals eaten outside school, which were more often snack-based. Sweetened beverages were more frequently reported outside school ( p < 0.001 for both sugar- and artificially sweetened beverages). Conclusion This study shows that despite access to free school meals, students in central Stockholm tend to leave school to consume less healthy lunches outside school. Combined with the easy access to vendors selling unhealthy foods and the frequent consumption of unhealthy snacks both in and outside school, these patterns highlight important public health concerns related to the school food environment. Overall, this study provides new insights into adolescents’ dietary patters during the school day, providing a foundation for future research and interventions supporting healthier eating among students.