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. 2016 May;103(5):1197-203.
doi: 10.3945/ajcn.115.121178. Epub 2016 Mar 30.

Universal equation for estimating ideal body weight and body weight at any BMI

Courtney M Peterson  1 , Diana M Thomas  2 , George L Blackburn  3 , Steven B Heymsfield  4
Affiliations

Universal equation for estimating ideal body weight and body weight at any BMI

Courtney M Peterson et al. Am J Clin Nutr. 2016 May.

Erratum in

Abstract

Background: Ideal body weight (IBW) equations and body mass index (BMI) ranges have both been used to delineate healthy or normal weight ranges, although these 2 different approaches are at odds with each other. In particular, past IBW equations are misaligned with BMI values, and unlike BMI, the equations have failed to recognize that there is a range of ideal or target body weights.

Objective: For the first time, to our knowledge, we merged the concepts of a linear IBW equation and of defining target body weights in terms of BMI.

Design: With the use of calculus and approximations, we derived an easy-to-use linear equation that clinicians can use to calculate both IBW and body weight at any target BMI value. We measured the empirical accuracy of the equation with the use of NHANES data and performed a comparative analysis with past IBW equations.

Results: Our linear equation allowed us to calculate body weights for any BMI and height with a mean empirical accuracy of 0.5-0.7% on the basis of NHANES data. Moreover, we showed that our body weight equation directly aligns with BMI values for both men and women, which avoids the overestimation and underestimation problems at the upper and lower ends of the height spectrum that have plagued past IBW equations.

Conclusions: Our linear equation increases the sophistication of IBW equations by replacing them with a single universal equation that calculates both IBW and body weight at any target BMI and height. Therefore, our equation is compatible with BMI and can be applied with the use of mental math or a calculator without the need for an app, which makes it a useful tool for both health practitioners and the general public.

Keywords: BMI; ideal body weight; obesity; overweight; simplified equations.

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Figures

FIGURE 1
FIGURE 1
Wt scales almost linearly with Ht. Although Wt scales as Ht2, Wt is a nearly linear function of Ht across the 95% Ht range (∼1.5–1.9 m). The example is for a BMI of 27 kg/m2 and shows the reference Ht (Ht0) of 1.5 m and ΔHt, which is the difference between an individual’s Ht and the reference Ht0. Ht, height; Wt, weight.
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Comment in

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