Title of article:

Body mass index as a measure of body fatness: age- and sex-specific prediction formulas

Authors: Deurenberg P, Weststrate JA, Seidell JC.
Journal: Br J Nutr, Mar 1991;65(2):105-14

Abstract

In 1229 subjects, 521 males and 708 females, with a wide range in body mass index (BMI; 13.9-40.9 kg/m2), and an age range of 7-83 years, body composition was determined by densitometry and anthropometry. The relationship between densitometrically-determined body fat percentage (BF%) and BMI, taking age and sex (males = 1, females = 0) into account, was analysed. For children aged 15 years and younger, the relationship differed from that in adults, due to the height-related increase in BMI in children. In children the BF% could be predicted by the formula BF% = 1.51 x BMI-0.70 x age - 3.6 x sex + 1.4 (R2 0.38, SE of estimate (SEE) 4.4% BF%). In adults the prediction formula was: BF% = 1.20 x BMI + 0.23 x age - 10.8 x sex - 5.4 (R2 0.79, SEE = 4.1% BF%). Internal and external cross-validation of the prediction formulas showed that they gave valid estimates of body fat in males and females at all ages. In obese subjects however, the prediction formulas slightly overestimated the BF%. The prediction error is comparable to the prediction error obtained with other methods of estimating BF%, such as skinfold thickness measurements or bioelectrical impedance.

Comments and Key points

The formula to predict your body fat percentage, based on your current BMI, age, and gender:

Child Body Fat % = (1.51 x BMI) - (0.70 x Age) - (3.6 x gender) + 1.4

Adult Body Fat % = (1.20 x BMI) + (0.23 x Age) - (10.8 x gender) - 5.4

where male gender= 1, female=0.

Well, this is just one possible body fat formula. Others exist1 from different authors, and some are specific to different races. But this formula is OK. But you should be aware that there is considerable variation in body fat percentage at any constant Body Mass Index.

References

  1. Jackson AS, Stanforth PR, Gagnon J, 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, Jun 2002;26(6):789-96

Review & comments by Steven B. Halls, MD, Last edited 23-June, 2008, Copyright.
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