Department of Management


Research output: Book/anthology/dissertation/reportPh.D. thesisResearch

This PhD thesis contributes with knowledge about adolescent healthy eating by studying consumer socialisation, social influence and behavioural change in relation to adolescent healthy eating. The introduction provides the important reasons for studying adolescents and healthy eating and explains that a more holistic approach is needed in order to respond to the rising levels of overweight among adolescents. It is important to understand the development of and influences on adolescent healthy eating behaviour and the possibilities for promoting healthy eating through interventions. By reviewing relevant literature on consumer socialisation, social influence and behaviour change through interventions employing feedback in relation to adolescent healthy eating, it is argued that a socio-cognitive approach to consumer socialisation and behaviour change provides a richer and more nuanced understanding of adolescent healthy eating. Based on this, the thesis presents three research questions which are investigated in three research papers. The research questions are:
1. Which roles do parents and adolescents have in healthy eating socialisation?
2. How does the social influence from parents and friends compared to personal factors impact adolescents’ healthy eating?
3. How can a feedback intervention based on socio-cognitive theory and using text messaging improve adolescent healthy eating and why?
The first research question is answered in research paper 1. Since the area of family interaction and family members’ roles regarding healthy eating socialisation is underexposed, the study aimed at exploring adolescents’ and parents’ awareness of and involvement in healthy eating and investigated how they related it to their roles in the healthy eating socialisation taking place within the family. As a follow-up on a healthy eating intervention, 38 adolescents and their respective families participated in depth-interviews and a practical exercise on daily fruit and vegetable intake. Results demonstrated that adolescents were found to adopt two strategies: a direct one placing demands on parents or a cooperative one helping parents. Parents initiated dialogues with family members about healthy eating and felt responsible as role models often fulfilling the adolescents’ demands and acknowledging their help. The findings confirm that parents still have the upper hand, when it comes to healthy eating, but with adolescents as active players confirming the notion of consumer socialisation as bidirectional processes. The study supplements previous research by including adolescents’ immediate family as a unit of analysis. By taking an intra-familiar systemic approach to studying family socialisation, this paper contributes with identifying and understanding barriers and facilitators of adolescents’ healthy eating.
The second research question is answered in research paper 2. The paper aimed at testing whether the common belief that children become increasingly influenced by friends at the expense of parents during adolescence is also true for healthy eating. Surveys were completed by 757 adolescent-parent dyads. The paper draws on Social Cognitive Theory and The Focus Theory of Normative Conduct and finds that parents remain the main influencer with what they do (descriptive norms) being more important than what they say (injunctive norms). The study contributes to a more comprehensive understanding of what influences adolescent healthy eating by comparing the influence of entangled social spheres (parents and friends) while also controlling for personal factors such as the adolescent’s self-efficacy and outcome expectations. No previous studies have included all these factors in the same analysis. The implications of the study are that (1) healthy eating interventions should aim at strengthening self-efficacy and positive outcome expectations among adolescents, (2) the family context should be included when implementing healthy eating interventions, and (3) parents’ awareness of their influence on adolescents’ healthy eating should be reinforced.
The third research question is answered in research paper 3. The paper investigated the effects of a healthy eating intervention by employing feedback via text messaging during 11 weeks in order to improve adolescents’ behaviour, self-efficacy and outcome expectations regarding fruit and vegetable intake. A pre- and post-survey was completed by 1488 adolescents randomly allocated to a control group and two experimental groups. Both experimental groups set weekly goals on fruit and vegetable intake, reported their consumption daily and subsequently received feedback on their performance via mobile text messaging (SMS). One of the experimental groups received, in addition, a 45-minute nutrition education session from a dietician during school. The direct effects of the interventions were not significant. However, for adolescents participating in the SMS routines, there were significant effects of the level of activity in the intervention, reflected in the number of sent text messages. Participants sending more than half of the possible text messages significantly increased their fruit and vegetable intake. Participants sending between 10 and 50% of the possible text messages experienced a significant drop in self-efficacy, and those sending less than 10% experienced a significant drop in outcome expectations. The findings suggest that participants’ active engagement in an intervention is crucial to its success. This has implications for the design and execution of health-promoting interventions.
Original languageDanish
PublisherAarhus University
Number of pages217
Publication statusPublished - 28 May 2015

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