Methodological problem with comparing increases in different measures of body weight

Helen L. Walls, Anna Peeters, Haider Mannan, Christopher Stevenson

    Research output: Contribution to journalArticlepeer-review

    3 Citations (Scopus)

    Abstract

    Background: A number of studies have compared proportional increases over time in waist circumference (WC) and body mass index (BMI). However this method is flawed. Here, we explain why comparisons of WC and BMI must take into account the relationship between them. We used data from two cross-sectional US surveys (NHANES 1988-94 and 2005-06), and calculated the percentage change in the average BMI and the average WC between the two surveys, comparing the results with a regression analysis of changes in WC relative to BMI. Findings. The crude percentage change in BMI (5.8%) was marginally greater than for WC (5.1%). But these percentages cannot be directly compared, as the relationship between the measures is described by a regression equation with an intercept term that does not equal zero. The coefficient of time from the regression equation will determine whether or not WC is on average larger for a given BMI at the second compared with the first time point. Conclusion: Differences in the percentage change in WC and the percentage change in BMI cannot be usefully directly compared. Comparisons of increases in the two measures must account for the relationship between them as described by the regression equation.
    Original languageEnglish
    Article number145
    Number of pages3
    JournalBMC Research Notes
    Volume4
    DOIs
    Publication statusPublished - 2011

    Open Access - Access Right Statement

    © Walls et al; licensee BioMed Central Ltd. 2011. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

    Keywords

    • body mass index
    • body weight
    • waist circumference

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