Optimum waist circumference‐height indices for evaluating adult adiposity: An analytic review

Abstract

Phenotyping adults for excess adiposity and related health risks usually include three body size measurements: height, weight and waist circumference (WC). Height and weight are now widely used as components of the body shape measure, body mass index (BMI, weight/height 2 ), with the height power referred to as the scaling factor, α. At present, WC is usually not adjusted for height or is expressed as WC/height in which α = 1. Although other α values have been proposed, a critical review of these shape measures is lacking. Here, we examine classical pathways by which the scaling exponent for height used in BMI was developed and then apply this strategy to identify the optimum WC index characteristic of adult shape. Our analyses explored anthropometric, body composition and clinically-relevant data from US and Korean National Health and Nutrition Surveys. Our findings provide further support for the WC index of WC/height 0.5 as having the strongest associations with adiposity while having the weakest correlations with height across non-Hispanic white and black, Mexican American and Korean men and women. The WC index, defined as WC/height 0.5 , when combined with BMI, can play an important role when phenotyping adults for excess adiposity and associated health risks in research and clinical settings. KEYWORDS adiposity, allometric analysis, body composition, body shape 1 | INTRODUCTION The search for diagnostic markers of excess adiposity and accompanying health risks is ongoing, with two main screening measures in current use: body mass index (BMI) and waist circumference (WC). 1 Current guidelines for the identification, evaluation and treatment of obesity incorporate both of these respective body shape and size measures as part of patient evaluation protocols. 2 Although the application of BMI (i.e. body weight/height 2 ) is relatively straightforward, less clarity surrounds the most appropriate index for waist circumference that reflects excess adiposity and health risks. Specifically, current obesity and metabolic syndrome guidelines promote the use of absolute waist circumference with sex and ethnicity-specific cut-off values, 3-5 and a large and growing literature advances observations surrounding the waist circumference/height ratio (WHtR) 6 or other similar waist circumference-stature ratios. 7,8 Should WC be adjusted for height (Ht)? If so, what is the optimum value of α in the index WC/Ht α ? The value of α in the WHtR is 1.0, and α in BMI (i.e. the height 'power' term) is 2.0. Over the past several years, our group has examined aspects of these questions 9-15 ; although there remains a specific need to clarify if and how to adjust waist circumference for between-individual differences in stature.

Comments on the article “Optimum waist circumference‐height indices for evaluating adult adiposity: An analytic review”: Relationships to previous studies

“…These negative values were also found by Han et al for Europeans . This, as well as Table 1, illustrates the importance of age in considering the height dependences of WC and body mass and therefore both α and p . In contrast, Table S9 indicates that there is conveniently little influence of age on correlations between WC and % fat and between body mass and % fat.…”

“…Figure 2 of Burton shows a strong correlation between p and α (with α there denoted q ) with most of the points being for data that were age‐adjusted or grouped for age . The tabulated results of Hwaung et al show similar relationships, for values both unadjusted and adjusted for age . Moreover, their eight age‐adjusted values, together with eight age‐adjusted values of Han et al, show a single clear straight‐line relationship, with a correlation coefficient of 0.91.…”

“…The recent review of Hwaung et al provides a detailed and valuable account of the history and rationale of the body mass index (BMI) and of indices relating waist circumference (WC) to body height that take the form WC/height α . I show here how their evidence and analysis are usefully supplemented with those of earlier studies.…”

When is sitting height a better measure of adult body size than total height, and why? The contrasting examples of body mass, waist circumference, and lung volume

“…Although statistical analysis produces precise values for p and q for any given sample, the exact value chosen in defining an index can be of little practical consequence, as illustrated by Benn (1971) and Hwaung et al (2020). Indeed, the definition of the BMI is accepted as BM/Ht 2 despite the fact that estimates of the exponent, q , are highly variable (even more so than in Table 2) and can be as low as 1.1 in women when BM and Ht are weakly correlated (Burton, 2007).…”

“…As indicators of adiposity, indices based on WC presently take the form of WC/Ht q , with q being taken as the round‐number values of 0, 0.5, or 1.0 (Browning et al, 2010; Burton, 2010; Nevill et al, 2017). However, exact values of q vary considerably with age range and fatness as is the case for BM (Hwaung et al, 2020). A q value of 1.0 is both dimensionally appropriate and convenient and that is true also of p in the index WC/SH p .…”