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Relationships between the Body Mass Index and body composition
R I Wellens1, A F Roche, H J Khamis
1Department of Community Health, Wright State University, Dayton OH 45387, USA.
Obesity Research
|January 1, 1996
Summary
Body Mass Index (BMI) is an uncertain measure of obesity. This study found BMI is a poor proxy for body fat percentage, especially in lower BMI ranges, and suggested new diagnostic cutoffs for obesity screening.
Area of Science:
- Human Physiology
- Anthropometry
- Body Composition Analysis
Background:
- Body Mass Index (BMI) is widely used to assess weight status.
- However, its accuracy as a proxy for body fat percentage (%BF) is debated.
- Understanding BMI's relationship with fat-free mass (FFM) is crucial for accurate health assessments.
Purpose of the Study:
- To evaluate Body Mass Index (BMI) as a proxy for percent body fat (%BF).
- To determine the association between BMI and fat-free mass (FFM).
- To identify optimal BMI screening cutoffs for obesity using densitometry data.
Main Methods:
- Utilized multivariate analysis of variance and partial correlations.
- Analyzed data from 504 men and 511 women (aged 20-45 years).
- Performed sensitivity/specificity analyses and Receiver Operator Characteristic (ROC) analyses.
Main Results:
- BMI showed stronger associations with %BF in higher BMI tertiles.
- In lower BMI tertiles, BMI correlated more strongly with FFM than %BF.
- BMI correctly identified only 44% of obese men and 52% of obese women based on %BF.
Conclusions:
- BMI is an uncertain diagnostic index for obesity.
- Current BMI cutoffs may misclassify individuals' body fat levels.
- Recommended BMI screening cutoffs for obesity are 25 kg/m2 for men and 23 kg/m2 for women.
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