Methodological problem with comparing increases in different measures of body weight

Walls, Helen L., Peeters, Anna, Mannan, Haider, and Stevenson, Christopher (2011) Methodological problem with comparing increases in different measures of body weight. BMC Research Notes, 4. 145. pp. 1-3.

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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.

Item ID: 35538
Item Type: Article (Research - C1)
ISSN: 1756-0500
Additional Information:

© 2011 Walls et al; licensee BioMed Central Ltd. 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.

Funders: National Health and Medical Research Council (NHMRC), VicHealth
Projects and Grants: NHMRC grant 465130
Date Deposited: 17 Oct 2014 00:14
FoR Codes: 11 MEDICAL AND HEALTH SCIENCES > 1117 Public Health and Health Services > 111706 Epidemiology @ 40%
01 MATHEMATICAL SCIENCES > 0104 Statistics > 010402 Biostatistics @ 60%
SEO Codes: 92 HEALTH > 9204 Public Health (excl. Specific Population Health) > 920499 Public Health (excl. Specific Population Health) not elsewhere classified @ 100%
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