This study contributes to the relatively understudied literature assessing the association between dietary behaviours, overweight/obesity, as well as mental health and well-being among adolescents. To our knowledge, this study is the first to analyse this relationship using the Swedish HBSC dataset. One additional novel feature of our work is that we have shown that meal patterns, that is the regularity with which adolescents consume breakfast and family meals, may be as important as diet quality measured as the frequency with which fruits, vegetables, sweets and SSBs are consumed. Furthermore, this is one of the first Swedish studies to explore the relationship between meal patterns and overweight/obesity among a nationally representative sample of adolescents 11–15 years old.

In relation to our key study aims, we observed that healthier dietary behaviours, such as the daily consumption of fruits, vegetables, family meals and breakfast, were associated with better mental health and well-being. Specifically, we found that adolescents who engaged in healthy behaviours were more likely to be satisfied with their lives, had lower psychosomatic complaints and school-related pressure. These relationships remained significant across the various health measures assessed, even after adjustment for potential confounders. We consistently observed that daily consumption of breakfast and family meals is linked to a higher likelihood of better mental health and well-being. However, the relationship between mental health and well-being and the consumption of fruits and vegetables showed some variability. These results were similar to those of previous studies assessing the relationship between dietary behaviours and mental health and well-being [16,17,18].

Although the results related to the consumption of SSBs and sweets were less consistent, the overall results indicated that consuming SSBs once per week or less was associated with higher life satisfaction, while the consumption of sweets and SSBs were both associated with a lower likelihood for adolescents to report two or more psychosomatic complaints more than once in a week and school-related pressure. These findings are similar to previous studies suggesting that sweets and SSBs was associated with poor health [30]. However, adolescents may potentially use these types of foods as a coping strategy for dealing with symptoms of mental ill-health, such as anxiety and stress [49,50,51].

Our findings further suggest that daily breakfast consumption is associated with a lower likelihood of overweight or obesity among adolescent. This finding echoes that of earlier studies indicating that breakfast may be a protective factor for unhealthy weight status and other negative health outcomes [6, 21, 26]. However, other dietary behaviours such as the consumption of fruits, SSBs and regular family meals did not show any significant associations with overweight or obesity. These findings are a departure from previous studies indicating that family meals [19] reduces the risk of obesity, and engaging in unhealthy dietary behaviours – low in the consumption of fruits and vegetables but high in the consumption of SSBs and sweets – is associated with overweight and obesity [13, 52]. It is worth noting that maintaining a healthy weight is a complex issue influenced through a complex interaction of genetic, environmental, psychosocial and behavioural factors [52].

The results of our study may have important implications for overweight/obesity, as well as mental health and well-being of adolescents. Similar to previous studies [11, 12], we found that the dietary behaviours of Swedish adolescents do not align with national recommendations [7]. Our findings also suggest that addressing the socioeconomic and demographic factors contributing to inequalities in health outcomes associated with dietary behaviours may reduce the risk of overweight/obesity while simultaneously increasing the likelihood of good mental health and well-being. This is because, consistent with previous studies [14, 15, 17, 29, 43, 47] we found that dietary behaviours vary across populations based on age, gender and socioeconomic status. Notably, boys tended to consume breakfast and partake in family meals more frequently than girls but consumed fruits and vegetables less frequently. Furthermore, adolescents from families with higher socioeconomic status, those with specific demographic attributes such as two-parent households and two Swedish-born parents, were more likely to engage in favourable dietary behaviours. These results echo those of earlier studies [17, 29, 47].

One should also keep in mind that a more holistic view of dietary behaviours may need to be adopted, given that previous studies have shown that there are significant associations between meal patterns and diet quality [10, 12, 13]. In addition, regular consumption of family meals and breakfast, may be indicators of well-functioning families, and that this may also influence mental health and well-being, as well as actual nutritional intake [20]. Moreover, at least one previous study showed that more frequent family dinners were associated with better mental health among adolescents. The association was partly attributable to improved parent-adolescent communication. Additionally, the health benefits appeared to be consistent across age groups and levels of family affluence [20]. The developmental stage of the study population may explain some of the observed findings. Prior research suggested that changes in dietary behaviours can occur naturally with age [43, 53]. As adolescents grow older, breakfast consumption might decline due to competition with their sleeping time, while increasing autonomy from parents is a typical developmental milestone, and this could contribute to fewer family meals [43].

Overall, the results from our study suggest that adopting healthy dietary behaviours have the potential to mitigate some of the risks related to overweight, obesity, and to improve the mental health and well-being of adolescents. Moreover, the findings underscore the significance of gaining a deeper insight into methods of improving mental health and well-being, as well as addressing the escalating rates of mental illness and issues with overweight and obesity in adolescents – which are key public health priorities [54]. Implementing policies that promote the intake of fruits and vegetables, decrease the consumption of SSBs and sweets, and emphasize the value of having breakfast and sharing family meals could offer a cost-effective public health intervention.

We have identified several strengths and limitations that should be considered when interpreting the findings and evaluating the results of this study. One key strength is the utilization of a large, representative population-based sample of Swedish adolescents, allowing for direct comparisons across various socioeconomic and demographic groups. The use of random sampling in the data collection process [45] enhances the statistical power and generalizability of the findings. Moreover, the selected survey questions have been derived from previous national studies and the HBSC international collaboration. The questions have therefore been tested across different populations, and have shown to be valid and reliable measures [45].

Another strength is the inclusion of socioeconomic and demographic confounders such as sex, age, parents’ country of birth, family type, FAS, perceived family wealth, and parents’ employment status in the regression models, which helps to minimize confounding effects and strengthens the validity of the associations examined.

Several limitations must be acknowledged. There are inherent limitations stemming from the use of cross-sectional data. This curtails our ability to deduce causal relationships and delve into complex associations (such as reverse causality, bi-directionality, and endogeneity) which are potentially present among the studied measures. For instance, the observed associations may have arisen from a relationship where the mental health and well-being of the adolescents determines their dietary behaviours. For example, as discussed above, it has been shown that stress is a key driver for unhealthy dietary behaviours, increasing the risk of consuming utraprocessed foods - sugary snacks, SSBs, packaged baked goods and ready meals - which are high in calories, sugar and fat [49,50,51]. Another limitation associated with using cross-sectional data is the issue of endogeneity. This arises due to the fact that respondents report their health and diet concurrently, this may contribute to potential correlations between these two responses. To comprehensively tackle these limitations, future research may benefit from using longitudinal data and/or intervention studies.

Furthermore, the HBSC study does not probe deeply into granular nutritional intake details. It focuses on the frequency of consumption for fruits, vegetables, SSBs, and sweets, without quantifying specific amounts, portion sizes, or calorie intake. Despite this constraint, the questionnaire is widely utilised and has been validated for assessing adolescents’ dietary patterns [14, 32, 42, 43, 45]. It is also crucial to highlight that these measures serve as indicators of healthier dietary behaviours and overall diet quality. Moreover, studies have shown that health behaviours tend to be closely interrelated [48]. For instance, the consumption of breakfast and family meals is often significantly linked to increased intake of fruits and vegetables [5].

Further research is necessary to provide clarity on specific study outcomes. In particular, future investigations should delve deeper into the complex relationships between dietary behaviours, weight status, and mental health. Understanding these complex interrelated issues is vital for creating comprehensive strategies to address the converging health issues faced by adolescents. This is because numerous factors shape dietary behaviours, including family and peer consumption patterns, food availability, broader food environments, and exposure to advertisements and marketing [1,2,3]. It is essential for future studies to disentangle the socioeconomic determinants that influence dietary behaviours and to understand the health disparities connected to these factors. Knowledge on these issues is essential for developing effective and targeted interventions, especially for individuals from low-income and vulnerable groups.