To identify the prevalence of unhealthy dietary behaviours and their social-ecological influences in adolescents.

The study used a sequential explanatory mixed-methods design, which begins with the collection of quantitative data, followed by the collection of qualitative data to explain and enrich the quantitative findings. Quantitative data were collected via a global school-based student health survey and were analysed using quantitative approaches. Qualitative data were obtained via focus group discussions and were analysed thematically.

Middle and high secondary schools in Taza city, Morocco.

Our quantitative analyses included 764 students (14–19 years). For the qualitative part, seventeen focus group discussions were conducted with 100 participants (fifty-six adolescents, twenty-six parents and eighteen teachers).

Of total student participants, 46·1 % skipped breakfast, 60·6 % had inadequate intake of fruits and vegetables (F&V), 39·4 % consumed soft drinks and 28·0 % consumed fast foods. All of these dietary behaviours could coexist in the same person except for inadequate intake of F&V. Gender, academic performance, age, perceived family income and education level of mother were associated with unhealthy dietary behaviours. Qualitative findings identified seven themes regarding social-ecological influences on adolescents’ dietary behaviours: cognitive, affective/biological, lifestyle, outcome expectation, social network, accessibility/availability and macro-level influences.

The prevalence of unhealthy dietary behaviours in our study group is a concern. Dietary behaviours are the result of inseparable interactions among social-ecological influences. Modifiable factors identified may be useful when designing a future intervention aimed at improving breakfast and F&V consumption and reducing fast/snack-food consumption among adolescents.