Main findings
The study revealed that body and weight concerns have unfavourable effects on subjective health and self-esteem, and that SRH and SE have mutually favourable effects on each other. Increased body mass had unfavourable effects on SRH, but these were less so for SE. The impact of body and weight concerns on SE was particularly strong among girls. In addition, we revealed that the intention of becoming thinner or fatter had strong paradoxical effects on body mass during the two years of the survey: the intention of getting thinner was associated with a BMI increase and the intention of getting fatter was associated with a BMI decrease. Positive SRH and SE were both associated with a leaner body after two years, and SRH was also associated with a beneficial BMI change during the two years’ observation.
The predictive association that we found between BMI and impaired SRH and SE is not always confirmed in the literature (23), and the relations seem both complex and reciprocal (24). We revealed these complex relations, similar to those found in the present study, in a lifestyle intervention study by two of the authors (EM and GBS) (25).
What is already known on this topic
SE and SRH were reciprocally related in the present study. Our findings are in line with previous research, that high levels of SRH at inclusion significantly predict improvements in self-conceptual measures, e.g. SE and body shape concern. Earlier studies often had a cross-sectional design (26, 27), however, and our findings add support for the mutual and reciprocal link over time between SRH and SE.
We also revealed that both SRH and SE were associated with a leaner body after the two years. The causal link was supported as high SRH was associated with less weight gain during the two years. In some studies, impaired SE served as a significant predictor for short-term, but not for long-term, weight loss (28). In line with the present findings, body satisfaction predicted a leaner body, whereas self-evaluative discontent with the body was related to weight gain (29). In addition, weight labelling from others predicted weight gain in early adolescence (3). Others report, however, non-significant associations between body image, SE, weight-specific quality of life, and BMI (30).
What this study adds
Overall, it appears that dissatisfaction and body distress may hinder attempts to lose weight, although multiple factors might confound this association (31). There is increasing concern, however, that a focus on weight is not only ineffective at producing thinner and healthier bodies, but may also have unintended consequences. It may contribute to food and body preoccupation, repeated cycles of weight loss and regain, and distraction from more sustainable health engagement. Reduced SE, eating disorders, and weight stigmatisation and discrimination could follow in the wake of a preoccupation with weight (8).
The results of the present study add evidence that these concerns are relevant. The various measures that we have used to describe body dissatisfaction are all associated with impairments in SRH and SE, both in temporal causal analyses and in residual change analyses. In addition, earlier research showed that body shape and weight concerns among adolescents have long-term health consequences, with increased infectious and other somatic morbidity in early adulthood (32). We have also documented a paradoxical effect of body dissatisfaction: that being eager to become thinner makes you fatter, and being eager to get fatter makes you thinner, compared with peers who are content with their bodies. Certainly, there are contesting explanations for these seemingly self-contradictory results. Genetic and other factors impacting weight regulation, working beyond and independently of human aspiration, are candidates for an alternative explanation (33).
Independent of such explanations, we are exposed to a dilemma: carrying excess weight and obesity are associated with ill health (9), but the clinical and public health efforts aimed at weight reduction may simultaneously represent a double-edged sword with unintended health impairments and paradoxical effects as results. Community- and school-based interventions are promising and may protect against stigmatizing effects and body dissatisfaction (34, 35). Non-diet interventions based on intuitive and mindful eating have led to weight reduction in studies with non-intervention controls (36), but the most important effects were that they promoted self-esteem, respect for body size diversity, and mitigated eating disorders (8). Some researchers, therefore, are calling for behaviour change approaches that improve psychological well-being in schools and in the general population (12, 37), e.g. SE, body satisfaction, SRH, and quality of life.
Limitations and strengths of this study
The weaknesses of the study include the large proportion of students lost to follow up, and possibly also the context of the study being set in mostly rural districts of western Norway. The large drop-out rate due to insufficient coding, especially in the youngest age group, represented a threat to the external validity of the study. Selective drop-out of those with better subjective health and fewer concerns with their own body may reduce the generalisability of the study. The drop-outs were random and not associated with participant characteristics. It is, therefore, unlikely that the predictive associations demonstrated in the study are invalid. Reliance on self-reports and an identical questionnaire at both time-points introduce the possibility of common method variance.
The strengths of the study are its longitudinal design and the evaluation of several predictors and outcomes. We examined both subjective health impairment, body mass and self-conceptual problems. Both mediation and moderation were examined, and we reported sex stratified analyses. We performed both temporal causal and residual change analyses. The study also adjusted for possible confounders, most important the self-rated socio-economic status that is linked with both body mass and subjective health.
The former county of Sogn og Fjordane is mainly a rural district, although urban areas exist. This setting may represent a threat to the external validity of the study. In several studies, however, two of the authors (EM and HJB) have demonstrated that adolescent health and health behaviour problems are similar to national and even international findings (20). We therefore maintain that the external validity of our findings seems safeguarded.