Body mass index: a scientific evidence-based inquiry

Area of Science:

• Anthropometry
• Human Physiology
• Biostatistics

Background:

• Body Mass Index (BMI) is a widely used metric for assessing body weight relative to height.
• However, BMI has limitations, particularly in accurately reflecting body composition and health status across different populations and age groups.
• There is a need for evidence-based alternatives to BMI that address these limitations.

Purpose of the Study:

• To critically evaluate the limitations of Body Mass Index (BMI).
• To propose and assess alternative methods for relating body weight and height.
• To identify evidence-based alternatives that improve upon BMI's shortcomings.

Main Methods:

• Analysis of weight and height data from children and adolescents (Brazil, US, Switzerland) and university students.
• Mathematical simulations using varying height (115-190 cm) and weight (25-105 kg) data.
• Comparison of three methods: BMI (weight/height²), reciprocal of ponderal index (height/weight¹/³), and ectomorphy.

Main Results:

• Mathematical simulations revealed strong associations among the three methods at a reference height of 170 cm.
• Discrepancies emerged in normal ranges at heights of 165 cm and 175 cm, indicating unfeasibility of direct index convertibility.
• The reciprocal of the ponderal index and ectomorphy demonstrated wider and more central ranges for both current and desired weights in university students and covered broader age ranges in children and adolescents.

Conclusions:

• The reciprocal of the ponderal index and ectomorphy are mathematically superior to BMI.
• These alternative indices offer greater logical consistency in assessing body weight and height.
• They can be applied with consistent cut-off points for normal ranges from age 5 onwards.