[Childhood obesity: definition, consequences, and prevalence]

Since the 1980s, an epidemic of obesity is occurring worldwide among adults and children. The body mass index (BMI) is useful to determine whether a child is overweight or obese because BMI relates strongly to body fat mass. However, contrary to adults, BMI changes with sex and age in children. Sex- and age-specific norms for BMI of the International obesity task force (IOTF) are now widely used. Approximately 15-20% of schoolchildren in Switzerland are currently overweight (or obese) and 2-5% are obese. Obesity is a major public health challenge. It is associated with numerous short and long term health hazards (in particular cardiovascular and metabolic disorders, e.g. diabetes) and it tracks form childhood throughout adulthood. This emphasizes the need for programs and polices aimed at preventing paediatric obesity.