Due to copyright issues, an electronic copy of the thesis must be ordered from the faculty. For the faculty to have time to process the order, the order must be received by the faculty at the latest 2 days before the public defence. Orders received later than 2 days before the defence will not be processed. After the public defence, please address any inquiries regarding the thesis to the candidate.
Trial Lecture – time and place
See Trial Lecture.
Adjudication committee
- First opponent: Professor Agneta Sjöberg, University of Gothenburg, Sweden
- Second opponent: Professor Elling Tufte Bere, University of Agder, Norway
- Third member and chair of the evaluation committee: Professor Jon Michael Gran, Faculty of Medicine, University of Oslo
Chair of the Defence
Associate Professor Valeria Vitelli, University of Oslo
Principal Supervisor
Associate Professor Mekdes Gebremariam, Faculty of Medicine, University of Oslo
Summary
Socioeconomic inequalities in children and adolescents’ body mass index (BMI), height and weight affect many countries across the globe, including high-income countries. Understanding when such socioeconomic inequalities occur, how they develop with increasing age and identifying the factors explaining these inequalities will inform the timing and potential targets of interventions aimed at tackling these inequalities. However, evidence in these areas is limited.
Dietary behaviours, including soft drink intake, are among the potential factors contributing to socioeconomic inequalities in childhood and adolescent overweight/obesity (OW/OB) and are influenced by factors at multiple levels. In regard, socioeconomic inequalities in several dietary behaviours among youth have been documented. Identifying the factors explaining socioeconomic inequalities in youth’s dietary behaviours may help to inform public health intervention targets to tackle these inequalities.
This PhD thesis aimed to explore (i) the occurrence and trajectories of socioeconomic inequalities in children's BMI, weight and height and ii) the mediators explaining socioeconomic inequalities in childhood and adolescence excessive weight gain (i.e., early excess weight gain at two years and OW/OB at five, eight and fourteen years) using data from the Norwegian Mother, Father and Child Cohort Study. The thesis also aimed to summarize existing evidence regarding mediators of socioeconomic inequalities in dietary behaviours among youth in general. Based on gaps identified in the review, mediators of parental education differences in the intake of carbonated drinks with added sugar (hereafter called soft drinks) were also explored.
The results of this thesis showed that differences in children's BMI trajectories by the maternal and paternal level of education were apparent at one month of age, persisting up to eight years. Differences in children's BMI trajectories by parental income occurred at nine months (for paternal income) and 18 months (for maternal income) of age and lasted up to eight years. Parental education and income differences in children's weight and height trajectories were observed from early infancy and continued up to eight years.
Exposure to risk factors of childhood and adolescent excessive weight gain during the prenatal and early postnatal period (up to two years) played a substantial role in explaining parental education differences in excessive weight gain in childhood and adolescence. The contribution of child energy balance-related behaviours in explaining parental education differences in OW/OB among children and adolescents was found relatively small.
Self-efficacy, food preferences and knowledge at the intrapersonal level; home availability, home accessibility, food rules and parental modelling at the interpersonal level were found as consistent factors explaining socioeconomic differences in dietary behaviours among youth. The results also showed research gaps targeting broader level factors that explain socioeconomic differences in dietary behaviours among youth. A cross-sectional study conducted based on the identified gap in the review showed that parental education differences in adolescent soft drink intake were explained by factors at intrapersonal and interpersonal factors (i.e., perceived accessibility of soft drinks at home, parental modelling for soft drink intake, and frequency of food/drinks purchased), but neighbourhood food environmental factors did not appear to explain the association. In addition, the results showed that the effect of parental education on adolescents' soft drink intake differs by neighbourhood income for its effect through perceived accessibility of soft drinks at home, demonstrating a stronger effect among those in low-income neighbourhoods.
Overall, this thesis demonstrated that socioeconomic inequalities in children’s body mass index and its composites occurred early in infancy and continued in childhood. The prenatal and early postnatal factors could be targeted for interventions combating the early emergence of socioeconomic inequalities in excessive weight gain during childhood and adolescence, as these factors explained most of the socioeconomic inequalities in excessive weight gain during childhood and adolescence. In addition, the modifiable risk factors of dietary behaviours at the intrapersonal and interpersonal levels could be targeted for interventions tackling inequalities in dietary behaviours among youth.
Additional information
Contact the research support staff.