Assessment and management of severe obesity in childhood and adolescence

The true prevalence of obesity in childhood is difficult to determine as there is no internationally accepted definition of pathological adiposity in the paediatric age group. Body weight is reasonably well correlated with body fat but is also highly correlated with height, and children of the same weight but different heights can have differing amounts of adiposity. In children the relationship between body mass index (BMI) and body fat varies considerably with age and with pubertal maturation. BMI centile charts using national BMI reference data have now been published in several countries and aid the graphical plotting of serial BMI measurements in individual patients. However, such charts are often based on arbitrary statistical measures and not on biological data related to the risk of later morbidity. Cole et al. developed age- and gender-specific cut-off lines from BMI data derived from six countries, which extrapolate risk from the adult experience to children (1). The International Obesity Task Force (IOTF) has recommended the use of these age- and gender-specific BMI cut-offs (overweight as approximately 91st percentile or greater and obesity as approximately 99th percentile or greater) for the comparison of obesity prevalence in different populations (2). Although there is no accepted definition for severe obesity in childhood, a BMI SD >2.5 (weight off the chart) is often used in specialist centres and the crossing of weight percentile lines upwards is an early indication of the risk of severe obesity.