Assessment of obesity in children and adolescents: synthesis of recent systematic reviews and clinical guidelines

This review summarises recent systematic reviews and evidence-based guidelines that deal with the issue of how best to diagnose or define obesity in children and adolescents. A recent systematic review showed that parents typically fail to recognise obesity in their children and adolescents, and a good deal of other evidence suggests that health professionals under-diagnose obesity in children and adolescents when using informal methods based on observation. There is therefore a need for practical, objective, methods that both identify the fattest children and adolescents adequately, and identify those who are at greatest risk of the ‘co-morbidities’ of obesity. A large body of consistent evidence shows that a high body mass index (BMI) for age and sex identifies the fattest children adequately, with low–moderate false negative rate and a low false positive rate. Furthermore, children and adolescents at high BMI for age are at much greater risk of the co-morbidities of obesity. A recent systematic review found that the use of BMI for age with national reference data and cut-off points (such as the 95th percentile to define obesity) was superior to the Cole–International Obesity Task Force international approach for defining obesity based on BMI for age. The same systematic review also found no evidence that use of waist circumference for age improved the diagnosis of obesity, or the cardio-metabolic co-morbidities of obesity, in children and adolescents. Recent systematic reviews are therefore supportive of current guidelines that recommend percentile-based cut-offs relative to national reference data to (e.g. BMI at or above the 95th or 98th percentile in the UK) to define obesity for clinical applications in children and adolescents.