Discordance of international adiposity classifications in Australian boys and girls - The LOOK study

Background: Various charts based on body mass index (BMI) and per cent body fat (�) are used to classify childhood body composition but outcomes may vary.

Aim: The study investigated variation in incidences of childhood obesity as depicted by four classification charts.

Subjects and methods: BMI and DXA-derived � were assessed in 741 children. Incidences of overweight and obesity were compared between two BMI charts and two bioelectrical impedance (BIA)-based � charts.

Results: The International Obesity Task Force (IOTF)-adopted BMI chart designated 21%, 6% (boys), and 26%, 9% (girls) as overweight and obese, respectively. Corresponding figures using the USA CDC BMI chart were 27%, 11% (boys) and 27%, 12% (girls). Using a USA-derived � chart incidences were 17%, 2% (boys) and 21%, 8% (girls) and using a UK-derived � chart 51%, 24% (boys) and 53%, 36% (girls). Sensitivity of BMI varied according to the � reference chart.

Conclusions: In contrast to the BMI-based charts, there were considerable variations in depicted incidences of obesity between the �-based charts. These discordances were considered to result from previously reported variation within and between BIA and DXA � assessments underlying the charts. The present study highlights the need for valid, reliable, unchanging BIA and DXA procedures.