BACKGROUND : Dieting is a risk factor of both eating disorders and obesity. The aim was to examine time trends of dieting in Swedish adolescents, and explore how dieting and body weight dissatisfaction are related to self-reported health, wellbeing and health behaviours. METHODS : Analyses of cross-sectional Swedish data from HBSC (Health Behaviour in School-aged Children) surveys 1994-2014. In total, about 30,000 girls and boys in the age of 11, 13 and 15 years participated. Data was collected by using classroom administered questionnaires in 5th, 7th and 9th grade. Logistic regressions was used to analyse secular trends of dieting, and how dieting and body dissatisfaction were associated with self-reported overall health, health behaviours, BMI and various physical, psychological and social aspects of health in 2014. RESULTS : Dieting increased from 1994 to 2014 in both girls and boys in all age groups, and in 2014, the prevalence was 14% in girls and 8% in boys. The prevalence of body satisfaction was 65% respectively 69%. Body weight dissatisfaction and dieting were present in all body weight classes and were associated with self-reported poor health and many other negative health aspects. In comparison with the participants that were satisfied with their body weight the odds ratio (95% CI) for self-reported poor health was 3.4 (2.6-4.4) in dieters, 4.9 (3.8-6.4) in participants who perceived a need to lose weight and 2.1 (1.5-2.8) in those who perceived a need to gain weight, when adjusting for age, sex and body weight class. CONCLUSIONS : When promoting health among school age children body weight dissatisfaction and dieting ought to be considered. Furthermore, it is important to support girls and boys in all weight classes to reach and maintain a healthy body image and weight.