TITLE:
Body Mass Exponential Index: An Age-Independent Anthropometric Nutritional Assessment
AUTHORS:
Manuel Cidrás
KEYWORDS:
Body Mass Index, Quetelet Index, Anthropometric Nutritional Status, Growth Rate, Weight-for-Height, BMI-for-Age
JOURNAL NAME:
Open Access Library Journal,
Vol.2 No.9,
September
25,
2015
ABSTRACT: Background: Body mass index (BMI) is a
squared-height power function. Nevertheless, some studies show a significant exponential weight-height correlation. Objectives: To demonstrate that the weight-height relationship from 2 to
20 years of age is better expressed by an exponential function. Design: 5th,
50th and 85th percentile weight-height curves according CDC 2000 Growth Charts.
A theoretical curve was created with the data on the 50th percentiles of weight
and height for each age, equivalent to the 50th percentile of the
weight-for-height curve. The statistical analysis was performed applying
regression analysis of the curve estimation in the power and exponential models.
Results: The exponential model correlation coefficient is higher than the power
model. The exponential model variable (1.9 in boys, 2 in girls) was
standardized to 2 to establish the body mass exponential index (BMEI): weight/exp(2*height).
Weight-for-age and exponential height-for-age fiftieth percentile curves show a
stable age-independent ratio near 2. These ratios are 1.5 and 2.5 for the 5th
and 85th percentiles, respectively. The shape of the well-known curve
BMI-for-age is due to the disparity between a exponential curve and a power
curve. Conclusions: An exponential function expresses the weight-height
relationship during growth better than a power function. A BMEI of 2 with
limits of 1.5 and 2.5 is useful for screening nutritional status during growth,
and the weight-for-height chart is an ideal substitute for the BMI-for-age
chart. The BMI-for-age curve shape and the disproportional BMI in taller
children are mathematical artifacts without biological meanings.