What are the cut-offs of BMI percentiles to define underweight, normality, risk of obesity and obesity (and its subclasses) in children and adolescents?
Despite the relatively wide acceptance of the use of BMI as an adiposity indicator, the establishment of a specific young obesity and overweight classification system has proved to be difficult. Constant changes in body composition during growth mean that the relationship between weight-for-height and adiposity during childhood and adolescence is age-dependent, and this relationship is further perplexed by race and gender. This is why BMI for children is gender and age specific and not calculated like the BMI for adults. BMI for children is plotted on gender specific growth charts.
These charts are used for children and teens 2 – 20 years of age. Each of the BMI for children gender specific charts contains a series of curved lines indicating specific percentiles. Healthcare professionals use the established percentile cut-off points to identify underweight and overweight in children. But there are several methods have been employed to define cut-off points for early overweight and obesity varying between countries. In addition to the country specific cut-off points, the IOTF (International Obesity Task Force) established international cut-off points of the BMI percentiles for children. These are the IOTF international cut-off points:Underweight
BMI-for-age < 5th percentile. Normal weight
BMI-for-age between 5th percentile and 90 percentile. At risk of overweight
BMI-for-age between 90th percentile and 97th percentile Overweight
BMI-for-age > 97th percentile.
BMI decreases during the preschool years, then increases into adulthood. The percentile curves show this pattern of growth. For example if the BMI for children places child at the 90th percentile, it means that compared to other children in its age, 90% have a lower BMI than itself. BMI for children is now the recommended method for screening overweight and underweight status in all children from 2 to 20 years of age. As a result of the alarming increase in the number of overweight children and adolescents, physicians are now going to be looking at BMI as well as eating and physical activity habits more closely as part of the regular pediatric check up.
Health Survey England - Anthropometric measurements, overweight, and obesity :
International Association for the Study of Obesity – IASO (incl. the IOTF)
BMI for Children - The International Survey
BMI chart for boys (from Germany following the IOTF cut-off points)
BMI charts for girls (from Germany following the IOTF cut-off points)