Objective The consequences of perceived obesity on qualitiy of life are compared with those of adolescents who are really obese.

Methods Within the framework of the German health survey of children and adolescents (KiGGS) the height and weight of the participants were measured. Children older than 11 years were asked whether they think they are underweight, of normal weight or overweight. To measure health-related quality of life (HRQoL) the internationally employed KINDL-R generic questionnaire was used and filled out by 4254 girls and 3415 boys, 11–17 years old.

Results The subjective assessment of body size differs markedly from the objective classification by the body mass index. Whereas 74.8% of the 11–17-year-old girls and boys are normal weight, only 40.7% think that their body size is all right. 49.4% of normal weight girls and 26.2% of normal weight boys think they are overweight. Within the group of obese adolescents, 60.6% of the girls and 31.2% of the boys admit to being obese. A comparison of the HRQoL scores between the group of obese and the group of subjectively assumed to be obese adolescents shows that the really obese people have better scores than those young people who only think they are overweight.

Conclusions A realistic body image of obese adolescents is the prerequisite to accepting intervention activities. The loss of quality of life resulting from perceived obesity, even for normal weight young people, illustrates the complexity of the fight against overweight and obesity.