Description
A healthy reference population, HRP, of zero underweight or overweight is considered as a standard population. The WHO Child Growth Standards on height and body mass are based on large samples in longitudinal (N=1737 children) and cross-sectional studies (N=6669) with similar numbers of girls and boys from Brazil, Ghana, India, Norway, Oman and the USA (1997-2003). Anthropometric studies carried out on adults since the 1960ies are prone to reflect the impact of high-caloric nutrition on allometric relationships, referring us to earlier time points for a HRP. The Committee on Biological Handbooks compiled a large dataset on height and body mass of healthy males from infancy to old age (CBH dataset, N=17523; Zucker 1962). The original studies were published between 1931 and 1944 and thus apply to a population (USA) before emergence of the fast-food and soft drink epidemic, and with a lifestyle demanding a balanced physical activity without the impact of local war or economic disaster on starvation.
Abbreviation: HRP
Reference: Body mass excess
Work in progress by Gnaiger E 2020-01-19 linked to a preprint in preparation on body mass excess, BME.
From BMI to BME
Four allometric phases
- The HRP is characterized by three allometric phases in childhood to early adolescence (up to 1.26 m height), and a final phase with an exponent of 2.867 (=1/0.35) at heights above 1.26 m, equal in women and men (Fig. 1; green line for MĀ° at BME=0).
- Figure 1: Four phases of the allometric relationship between body mass, MĀ°, and height, H, in the healthy reference population (HRP), and shift of M at body mass excess, BME, indicating underweight (BME = -0.2 and -0.1) or overweight (BME = 0.2) and increasing degrees of obesity (BME = 0.4 to 1.0).
- At any given height, the personal body mass may deviate from the reference body mass, MĀ°, in the HRP for the same height. This difference is the excess body mass, ME = M-MĀ°, is normalized for MĀ°, we obtain the simple definition of the body mass excess, BME = ME/MĀ°. By this definition, the BME equals zero in the HRP at all heights. For comparison, it is instructive to calculated the BMI as a function of height in the HRP, defining this as the BMIĀ° or precision BMI at BME=0. The normal BMI of 20 kgĀ·m-2 is obtained in the HRP at H=1.7 m and MĀ°=57.7 kg/x. If this normal BMI would represent a general index independent of height, it should be constant for the HRP, which is clearly not the case, neither for adults nor children (Fig. 2).
- Figure 2: Precision reference body mass index, BMIĀ°, with the BMIĀ°=20 kgĀ·m-2 at the height of 1.70 m in the healthy reference population (dashed lines). The circle marks the harmonization point between the BMI of 20 kgĀ·m-2 (normal) and the precision BMIĀ°. For persons smaller than 1.7 m, the BMIĀ° is below 20 kgĀ·m-2, such that a BMI of 17.9 instead of 20 kgĀ·m-2 is the precision reference at a height of 1.5 m. On the other hand, at a height of 1.9 m a BMI of 22 instead of 20 kgĀ·m-2 is the precision reference (dotted lines).
- The concept of body mass excess, BME, is simple and easy to communicate to the general public. In contrast, neither the BMI nor the concept of a precision BMI can be explained easily. With the BMI firmly established by convention in the WHO, however, it is important to harmonize the concepts of BME and BMI. Fig. 2 provides the first step for harmonization by assigning to the height of 'reference man' (Sender 2016 PLOS Biol) the BMI of 20 kgĀ·m-2 as BMIĀ°. BME cutoff points for overweight and obese are then obtained for BMI cutoffs of 25 and 30 kgĀ·m-2 at heights of 1.79 and 1.85 m, respectively.
- Ā» Further details: BME cutoff points).
- Figure 3 is based on the WHO Child Growth Standards [1-3]. It illustrates the limitation of the BMI as an index of overweight and obesity. The precision body mass index, BMIĀ°, is claculated for the healthy reference population (HRP), in which neither underweight nor overweight prevails and which, therefore, should be characterized by a constant index. This is achieved by the body mass excess, BME [4], which relates the actual body mass, M, to the reference body mass, MĀ°, at a given height, BME=(M-MĀ°/MĀ°). The BME is constant at 0.0 for the HRP for both sexes independent of height. In contrast, the increase of the precision BMIĀ° from 15 to 21 kgĀ·m-2 from 1.0 to 1.8 m represents a confounding factor which explains the necessity of adjusting the BMI cutoff points. Instead of a focus on adjusted BMI cutoff points [3], research should focus on evaluation of the concept of BME and the HRP.
MitoPedia: BME
References
- WHO Multicentre Growth Reference Study Group (2006) WHO child growth standards based on length/height, weight and age. Acta PƦdiatrica Suppl 450:76-85.
- WHO Multicentre Growth Reference Study Group (2006) WHO child growth standards: length/height-for-age, weight-for-age, weight-for-length, weight-for-height and body mass index-for-age: Methods and development. Geneva: World Health Organization:312 pp.
- de Onis M, Onyango AW, Borghi E, Siyam A, Nishida C, Siekmann J (2007) Development of a WHO growth reference for school-aged children and adolescents. Bull World Health Organization 85:660-7.
- Zucker TF (1962) Regression of standing and sitting weights on body weight: man. In: Altman PL, Dittmer DS, eds: Growth including reproduction and morphological development. Committee on Biological Handbooks, Fed Amer Soc Exp Biol:336-7. ā Anthropometry, H and MĀ°, of the healthy reference population, HRP; based on [3.1-3.5]. - Ā»Bioblast linkĀ«
- Bayley N, Davis FC (1935) Growth changes in bodily size and proportions during the first three years. Biometrika 27:26-87.
- Gray H, Ayres JG (1931) Growth in private school children. Behavior Res Fund Monog, Univ Chicago Press, Chicago:282 pp. ā With averages and variabilities based on 3110 measurings on boys and 1473 on girls from the ages of one to nineteen years.
- Meredith HV (1935) Univ Iowa studies in child welfare 11(3).
- Peatman JG, Higgons RA (1938) Growth norms from birth to the age of five years: a study of children reared with optimal pediatric and home care. Am J Diseases Children 55:1233-1247.
- Simmons KW (1944) Monographs Soc Research in Child Develop 9(1).
- Body mass excess
MitoPedia concepts:
MiP concept
Labels:
MitoPedia:BME