[The implications of using different body mass index references in children and adolescents]

To classify children as overweight or obese, their body mass index (BMI) must be compared with a growth reference and be accompanied by a clinical assessment. In Denmark, there is a lack of consensus on which BMI reference to use; a mix of national and international references are used in clinics, hospitals and research institutions. In this article, the implications of using different references are illustrated with Danish data. The comparisons show that the references yield different prevalences of overweight in a non-predictable way, making comparisons and monitoring challenging.