Excecutive summaryBackground: The spectrum of weight related disorders refers collectively to conditions of overweight and obesity as well as disordered eating behaviour and eating disorders. Paradoxically, dieting predicts increased body weight, augmented body dissatisfaction, and increased risk of developing an eating disorder. Some studies show that moderate dieters have a more adequate dietary intake than non dieters; others suggest that dieting predicts a behavioural pattern that is counterproductive to sound weight management. The range of weight control behaviours includes both healthful eating behaviours generally recommended for good health, as well as potentially dangerous behaviours such as starving, vomiting and use of laxatives. Qualitative studies suggest overlap in the understanding of dieting and general healthful eating. Slimming is used in this thesis about the general concept of attempting to reduce body weight. While the term dieting refers to changes in the diet, the term Slimming refers to the activity of reducing weight, and was considered a better translation of the Norwegian term slanking that was investigated in this thesis. A better understanding of what adolescent girls mean when they talk about slimming is needed to interpret prevalence of self reported slimming, as well as for development of good questionnaires for future studies, and good interventions aimed at healthful weight development. The present study aimed to explore Norwegian adolescent girls perceptions of healthiness and slimming as well as the distinction between the two concepts. Methods: Eight semi-structured focus group discussions with a total of 52 participants (28 girls 11 years of age and 24 girls 15 years of age) were conducted during the winter 2006 / 2007 in suburban schools near Oslo. Focus group discussions were carried out in the school setting, during school hours, each lasting for about 45 minutes. Participants were asked questions about their perceptions of healthiness and slimming behaviours. Digital recordings of the discussions were transcribed verbatim, and transcripts were analysed according to recommendations made by Morgan and Krueger, and Dahlgren. Findings: Healthiness was discussed as a healthful lifestyle including both a healthful diet and physical activity. Participants had knowledge about healthful foods and eating habits, and considered balance, moderation and variation important characteristics of a healthful lifestyle. The motivating factors in terms of healthful behaviours were having fun and school performance among the younger girls, while appearance was the main driving force among the older participants. Slimming was viewed as an expression of body dissatisfaction and a desire to loose weight by participants of both ages. Physical activity, healthful food choices, reducing food intake and skipping meals, use of slimming products and eating disorders were discussed as weight control behaviours. Slimming was perceived to be uncommon among 11 year old girls, and common among 15 year old girls although mostly as short term efforts related to season and special events. Concerns about weight and appearance were considered by the older participants to be universal among their peers. The 15 year old girls expressed some concern about development of eating disorders as a result of the ineffectiveness of slimming. Conclusion: The findings indicate that slimming does not necessarily imply actual behavioural changes among adolescents. The focus on satisfaction/dissatisfaction with own body and on the intention behind the behaviour when distinguishing between healthiness and slimming means that the behaviours of adolescents who are interested in a healthful lifestyle and those who are interested in slimming might not actually differ at all, but that the difference lies in the mindset. Although healthful behaviours might be undertaken by adolescents seeking to loose weight, there can still be a negative effect of the slimming in terms of mental health; being dissatisfied with their own body and continuing to become even more dissatisfied when not achieving the desired effect. This, in turn may lead to use of more extreme weight control behaviours over time.