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BMI-related errors in the measurement of obesity


Body mass index (BMI) has various deficiencies as a measure of obesity, especially when the BMI measure is based on self-reported height and weight. BMI is an indirect measure of body fat compared with more direct approaches such as bioelectrical impedance. Moreover, BMI does not necessarily reflect the changes that occur with age. The proportion of body fat increases with age, whereas muscle mass decreases, but corresponding changes in height, weight and BMI may not reflect changes in body fat and muscle mass. Both the sensitivity and specificity of BMI have been shown to be poor. Additionally, the relation between BMI and percentage of body fat is not linear and differs for men and women. The consequences of the errors in the measurement of obesity with BMI depend on whether they are differential or nondifferential. Differential misclassification, a potentially greater problem in case–control and cross-sectional studies than in prospective cohort studies, can produce a bias toward or away from the null. Nondifferential misclassification produces a bias toward the null for a dichotomous exposure; for measures of exposure that are not dichotomous, the bias may be away from the null. In short, the use of BMI as a measure of obesity can introduce misclassification problems that may result in important bias in estimating the effects related to obesity.

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  1. Cohn SH . New concepts of body composition. In: Ellis KJ, Yasumura S, Morgan WD (eds) In Vivo Body Composition Studies. The Institute of Physical Sciences in Medicine: London, 1987. pp 1–14.

    Google Scholar 

  2. Jackson AS, Stanforth PR, Gagnon J, Rankinen T, Leon AS, Rao DC et al. The effect of sex, age and race on estimating percentage body fat from body mass index: The Heritage Family Study. Int J Obes Relat Metab Disord 2002; 26: 789–796.

    Article  CAS  Google Scholar 

  3. Nawaz H, Chan W, Abdulrahman M, Larson D, Katz DL . Self-reported weight and height: implications for obesity research. Am J Prev Med 2001; 20: 294–298.

    Article  CAS  Google Scholar 

  4. Deurenberg P, Andreoli A, Borg P, Kukkonen-Harjula K, de Lorenzo A, van Marken Lichtenbelt WD et al. The validity of predicted body fat percentage from body mass index and from impedance in samples of five European populations. Eur J Clin Nutr 2001; 55: 973–979.

    Article  CAS  Google Scholar 

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Correspondence to K J Rothman.

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Rothman, K. BMI-related errors in the measurement of obesity. Int J Obes 32 (Suppl 3), S56–S59 (2008).

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