Hood 2019 Nutr Diabetes

Hood K, Ashcraft J, Watts K, Hong S, Choi W, Heymsfield SB, Gautam RK, Thomas D (2019) Allometric scaling of weight to height and resulting body mass index thresholds in two Asian populations. Nutr Diabetes 9:2. doi: 10.1038/s41387-018-0068-3.

» PMID: 30683839 Open Access

Hood K, Ashcraft J, Watts K, Hong S, Choi W, Heymsfield SB, Gautam RK, Thomas D (2019) Nutr Diabetes

Abstract: BACKGROUND: Body mass index (BMI) represents a normalization of weight to height and is used to classify adiposity. While the capacity of BMI as an adiposity index has been experimentally validated in Caucasians, but there has been little testing Asian populations.

METHODS: To determine whether weight scales to height squared in Asian Indians across the general population and in Asian Indian tribes an allometric analysis on the power law model, W =αHβ, where W is weight (kg) and H is height (m) was performed on cross-sectional weight and height data from India (N = 43,880) collected through the Anthropological Survey of India. The database contained males 18-84 years of age spanning 161 districts of 14 states and including 33 different tribes (N = 5,549). Models were developed that were unadjusted and adjusted for tribe membership. The Korean National Health and Nutrition Examination Survey (KNHANES) was used to compare to height-weight data from the Anthropological Survey of India and to calculate BMI thresholds for obesity status using a receiver operating characteristic.

RESULTS: The unadjusted power was β = 2.08 (s = 0.02). The power for the general population (non-tribal) was β = 2.11 (s = 0.02). Powers when adjusted for tribe ranged from 1.87 to 2.35 with 24 of the 33 tribes resulting in statistically significant (p < 0.05) differences in powers from the general population. The coefficients of the adjusted terms ranged from -0.22 to 0.26 and therefore the scaling exponent does not deviate far from 2. Thresholds for BMI classification of overweight in the KNHANES database were BMI = 21 kg/m2 (AUC = 0.89) for males 18 kg/m2 (AUC = 0.97) for females. Obesity classification was calculated as BMI = 26 kg/m2 (AUC = 0.81) and 23 kg/m2 (AUC = 0.83) for females.

CONCLUSIONS: Our study confirms that weight scales to height squared in Asian Indian males even after adjusting for tribe membership. We also demonstrate that optimal BMI thresholds are lower in a Korean population in comparison to currently used BMI thresholds. These results support the application of BMI in Asian populations with potentially lower thresholds.

• Bioblast editor: Gnaiger E

From BMI to BME

Work in progress by Gnaiger E 2020-02-03 linked to a preprint in preparation on BME and mitObesity.

Figure 1: Body mass as a function of height. The full lines show the allometric relation of the healthy reference population with body mass M° (BME°=0.0; green), at a body mass excess of BME=0.2 (M_0.2=1.2M°; orange), and at BME=-0.1 (M_-0.1=0.9M°; blue). Symbols are from Table 1 of Hood et al (2019) with the years of measurement in parentheses. Healthy and active adult males (15–54 years) were studied in 34 tribal populations from 14 of the 29 states of India (N=5549) and nontribal populations in each state (N=38331) from 1965 to 1970 and from 2005 to 2006. The dashed line connects the average of 5089 women and 3849 men of South Korea collected from 2007–2009 (KNHANES IV) and 2010–2012 (KNHANES V).

Hood et al (2019) suggest that their study 'confirms that weight scales to height squared'. Do their and many similar studies qualify for more than the trivial statement: 'Without reference to a rational (mechanistic, physiolgocial, evolutionary, ..) hypothesis, the relationship observed between body mass and height in this particular database does not provide evidence for or against a specific exponent in the allometric body mass/height power function'. The assumption that body mass scales to height squared in various present-day populations has no rational foundation (this challenges the corresponding working hypotesis). It is important, therefore, to define the fundamental hypothesis, upon which a judgment of the power function with an exponent of two carries heuristic relevance. A 'fundamental' hypothesis cannot be gauged on mere convention and historical track record (think of the religious and scientific believes in the heliocentric world-view). An allometric power function can be calculated from any data collected recently on any population of the world. So what? There is a solidly documented global trend towards increased overweight and obesity (##). Importantly, however, there is strong evidence that different socio-economic subgroups of a population (women versus men, children versus adults, large versus small, affluent versus poor) are affected differently by the general trend towards obesity. Consequently, the allometric height exponent A (A=2 in the BMI paradigm) observed in any current study reveals interesting information on the differential trends towards obesity, without any relevance on the general anthropomorphic concept of the BMI.

The relevant questions and directions of research are: (1) Define the allometric healthy reference population (HRP). WHO standars provide an invaluable resource. (2) Forge WHO standars and additional historical resources into basline paramters. These need to be validated across:

1. Evolutionary background: the bias of different heights in the adult population is fundamentally explained by the BME-concept.
2. Gender or sex: BME cutoff points are valid equally in women and men, in contrast to a unresolved debate to channels all interests in a single channel.

Labels: MiParea: Gender, Exercise physiology;nutrition;life style  Pathology: Obesity 

Organism: Human 

Preparation: Intact organism 

BMI, BMI-cutoff, BME