In contrast, BMI, which is defined as body weight divided by height squared (kg/m 2), is now more widely used in clinical settings to diagnose excess adiposity and underweight status ( 9– 11). For these reasons, IBW equations have largely been replaced by BMI ranges. ( 2) analyzed IBW equations and showed that they were incompatible with BMI and, instead, that IBW equations underestimated body weight at shorter heights and overestimated body weights at taller heights ( 2). Second, IBW equations predict a single target body weight, whereas most clinicians favor, and the empirical data support, a range of target body weights. First, although IBW or desirable weight was originally defined as the weight associated with the greatest life expectancy at each height, there is no single ideal weight that applies universally to all comorbidities and mortality-specific causes, and there is no single ideal weight that is applicable across all demographic factors, including age and ethnicity ( 8). However, despite the advantage of simplicity, the IBW approach has 3 important limitations. The simple linear structure of these equations makes them easy to calculate with the use of mental math or a calculator.
The advantage of IBW equations is that they predict weight (variable: Wt) as a linear function of height (variable: Ht) as Although not as popular as they once were, IBW equations are still being used by clinicians to calculate drug dosing, to estimate overweight and underweight statuses, and to calculate nutrient intakes ( 2). More recently, Hammond ( 7) created a metric version of the Hamwi equation. ( 6) formulated IBW equations on the basis of the 19 Metropolitan Life Insurance Company height-weight tables, respectively. A decade later, motivated by applications to drug dosing, Robinson et al. Later, the popularity of IBW equations increased after Hamwi ( 3) and Devine ( 4) published their seminal equations ( 4). Because these tables are cumbersome to use, ideal body weight (IBW) equations for predicting weight as a linear function of height were developed starting in the late 1800s ( 2). Many of the first attempts were based on actuarial data and defined ideal or desirable body weights with the use of height-weight tables.
Ideal body mass index calculator how to#
How to accurately determine desirable or target body weights for nutritional and health assessments has been an important challenge for more than a century ( 1, 2). 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. 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.Ĭonclusions: 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. 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. We measured the empirical accuracy of the equation with the use of NHANES data and performed a comparative analysis with past IBW equations. 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.ĭesign: 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. 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. 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.
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