Classification of obesity varies between body mass index and direct measures of body fat in boys and girls of Asian and European ancestry

J. McConnell-Nzunga, P. J. Naylor, H. Macdonald, R. E. Rhodes, Scott Hofer, H. McKay

Research output: Contribution to journalArticle

4 Scopus citations


Body mass index is a common proxy for proportion of body fat. However, body mass index may not classify youth similarly across ages and ethnicities. We used sex- and ethnic-specific receiver operating characteristic curves to determine how obesity classifications compared between body mass index and dual energy x-ray absorptiometry-based body fat percent. Male and female participants 9- to 18-years-old (n = 944; 487 female) were measured 1 to 13 times (1999–2012; 4,411 observations). Body mass index identified < 50% of those classified as obese from body fat percent. Specificity was 99.7%, and sensitivity was 35.8%. Using area under the curve and standard error values, body mass index performed significantly better for: Male versus female at 10 years, Asian versus European female except at 13-, 15-, and 16-years-old, Asian female versus male except at 10- and 15-years-old, and for European male versus female, 9- to 11-years-old (p < .05). Our findings provide evidence that users of body mass index should use caution when comparing body mass index across age, sex, and ethnicity.

Original languageEnglish (US)
Pages (from-to)1-13
Number of pages13
JournalMeasurement in Physical Education and Exercise Science
Publication statusAccepted/In press - Dec 15 2017
Externally publishedYes



  • BMI
  • body fat
  • ethnicity
  • measurement
  • obesity

ASJC Scopus subject areas

  • Orthopedics and Sports Medicine
  • Physical Therapy, Sports Therapy and Rehabilitation

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