Title of article:

Is body mass index a measure of adiposity in elderly women?

Authors: Bedogni G, Pietrobelli A, Heymsfield SB et al.
Journal: Obes Res, Jan 2001;9(1):17-20

Abstract

OBJECTIVE: To evaluate the accuracy of body mass index (BMI) as a predictor of body fat in elderly women. RESEARCH METHODS AND PROCEDURES: A total of 1423 women aged 67 +/- 5 (mean +/- SD, range: 60 to 88) years were consecutively enrolled into the study. Fat mass (FM) was measured using DXA. RESULTS: BMI explained 72.9% of FM variance (p < 0.0001), with a root mean square error of estimate (RMSE) of 3.5 kg. After standardization of RMSE on the dependent variable as RMSE%, the prediction error equaled 15%. BMI explained 54.8% of FM% variance (p < 0.0001), with an RMSE of 4.1%, corresponding to an RMSE% of 11%. DISCUSSION: The relatively high RMSE% of the FM and FM%-BMI associations caution against the use of BMI as an adiposity index in individual elderly women. However, an error corresponding to 11% of FM% may be accepted for population studies of body fat in elderly women.

Comments and Key points

This article has an impressive sample size of elderly women, age 60 to 88 years. Their data graphed looks like this, showing body fat percentage versus Body Mass Index.

A couple of points about this graph. They used a linear trend line, but a curving line would have been a little better. I've compared this data (above) of average 67-year old women, compared to the Heritage Family study¹ data of American women, average age 34. I've superimposed the current elderly data (red) over the Heritage Family study data ( light grey circles).

It is not unexpected that the (red) elderly women would have a higher body fat percentage, by about 5%, compared to younger adult women.

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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