Applications of BMI or BSI: Differences and Revisions According to Age and Height

Abstract

Validation of body-mass relationships requires a careful statistical analysis of data of normal weight individuals. BMI (ratio between body mass and square of body height) and BSI values (ratio between mass and cube of body height) have been calculated for 99 persons with ages between 1 day and 76 years. These BMI or BSI values have been used for least squares fits yielding mean BMI or BSI values, their variances (providing precision), and average deviations of individual BMI/BSI values from the BMI/BSI means. The latter allows limits to over- and underweight. For adults we found mean values of BSI of 12.36 and confirmed 21.7 for the mean BMI; but the BSI was 1.4 times more precise than the BMI. For children shorter than 1.3 m and younger than 8 years we found the BMI average of 15.9 and over-/underweight limits of 17.4/14.4 being significantly smaller than and incompatible with the recommended BMI values.

Indexing adult obesity by waist-to-height and weight-to-height ratios

“…Both seem extraordinary as the cylindrical model of human body, if proportions were preserved, prompts a cubic dependence of weight on height. [24] Of note, in some cultures fatness of women is regarded an attribute of married status, or this is a refraction of the population genetic propensity to obesity. Generally, if the amount of accumulated fat becomes extremely high then the cubic model may indeed suit better.…”

“…2) is that this helps to "tame" the effect of weight variation, granted that height is much more stable a measure than weight. [24] The lack of guidance as to "how and when", may partly be behind the spread arrangement whereby weight, instead of being measured, is simply elicited from the subjects of screening or, equivalently, transferred from other databases. This kind of information is often obsolete.…”

“…Again, BMI 2 is an obvious choice in relation to pain in weight-bearing joints because it characterises the pressure in a joint, [24] which was probably another historical reason behind the wide acceptance of BMI 2 as a universal measure of excessive weight. However, it is unnecessary that the extra weight was associated with adiposity, it can refer to a burden of any kind, even related to carrying loads.…”

Correspondence between waist-to-height ratio and body mass index in juniors

“…Above all, this threshold is still lower than the "right" BMI, discussed in the introduction, which is 21.5 kg/m 2 for adults. [23] In fact, it is half-way between the healthy and the right. It makes sense to embrace this uniform approach for the junior population, and it is achievable by distancing BMI category levels at any age by the width of the overweight band.…”

“…Included in this table is also the healthy limit and the "right" (mean) level of BMI (tracing the WHO SD 0 curve). The right BMI is assumed to be 21.5 kg/m 2 at 20 years, [23] which guidelines do not specifically quote, but the female data most closely match the adult thresholds overall, and this value is set accordingly. The piece-wise-linear-approximate, anygender overweight and obese boundaries in the Age -BMI space, adjusted to match adult levels at 20 years, are shown in Figure 2 together with the gender-specific boundaries according to WHO.…”