# Diagnostic Performance of BMI and Waist Circumference in Detecting Excess Adiposity

## TL;DR

The study compares BMI and waist circumference in detecting excess body fat, finding that waist measures are more sensitive but less specific than BMI.

## Contribution

The study evaluates the Lancet Commission criteria alongside BMI and waist circumference for detecting adiposity using DEXA, revealing their comparative diagnostic performance.

## Key findings

- Waist-based measures showed higher sensitivity but lower specificity than BMI for detecting excess adiposity.
- The Lancet Commission criteria performed similarly to existing BMI and waist thresholds.
- Race-specific BMI thresholds did not improve diagnostic accuracy.

## Abstract

This study compared the diagnostic performance of BMI, waist circumference (WC), and Lancet Commission (LC) criteria for assessing excess adiposity measured by dual‐energy X‐ray absorptiometry (DEXA) in US adults.

Using 2011–2018 NHANES data, we included 10,747 adults aged 20–59 years with relevant data. We evaluated the diagnostic performance (sensitivity, specificity, positive and negative predictive values [PPV, NPV], area under the curve [AUC]) of BMI thresholds, waist‐based measures, and LC criteria for excess adiposity, as defined by DEXA.

The weighted prevalence of DEXA‐defined excess adiposity was 36.4%. CDC BMI thresholds demonstrated 74.6% sensitivity and 82.2% specificity (PPV, 67.0%; NPV, 87.0%). Waist‐based measures showed higher sensitivity and lower specificity than BMI; NHLBI WC thresholds produced 88.5% sensitivity and 66.7% specificity. LC criteria performed variably: BMI plus ≥ 1 waist measure had 74.6% sensitivity and 82.2% specificity, whereas ≥ 2 waist measures had 88.5% sensitivity and 66.8% specificity. The AUC values were 0.876 for BMI, 0.882 for WC, 0.887 for waist to height ratio, and 0.715 for waist to hip ratio.

Waist‐based definitions were more sensitive than BMI, whereas BMI provided greater specificity. LC criteria performed comparably to existing definitions. Incorporating WC into screening may improve the detection of excess adiposity.

What is already known?○BMI is widely used to define obesity. However, BMI is an inferior prognosticator of central adiposity and cardiometabolic risk compared to waist circumference (WC).○New guidelines, such as the 2025 Lancet Commission criteria, propose integrating BMI and WC for better adiposity assessment.
What does this study add?○WC‐based definitions were more sensitive but less specific than BMI for detecting excess body fat; race‐specific BMI thresholds did not improve diagnostic accuracy.○The Lancet Commission criteria performed similarly to current BMI and WC thresholds.
How might these results change the direction of research or focus of clinical practice?○These results support the incorporation of WC alongside BMI in obesity screening and encourage further validation of combined anthropometric criteria across diverse populations.

What is already known?○BMI is widely used to define obesity. However, BMI is an inferior prognosticator of central adiposity and cardiometabolic risk compared to waist circumference (WC).○New guidelines, such as the 2025 Lancet Commission criteria, propose integrating BMI and WC for better adiposity assessment.

BMI is widely used to define obesity. However, BMI is an inferior prognosticator of central adiposity and cardiometabolic risk compared to waist circumference (WC).

New guidelines, such as the 2025 Lancet Commission criteria, propose integrating BMI and WC for better adiposity assessment.

What does this study add?○WC‐based definitions were more sensitive but less specific than BMI for detecting excess body fat; race‐specific BMI thresholds did not improve diagnostic accuracy.○The Lancet Commission criteria performed similarly to current BMI and WC thresholds.

WC‐based definitions were more sensitive but less specific than BMI for detecting excess body fat; race‐specific BMI thresholds did not improve diagnostic accuracy.

The Lancet Commission criteria performed similarly to current BMI and WC thresholds.

How might these results change the direction of research or focus of clinical practice?○These results support the incorporation of WC alongside BMI in obesity screening and encourage further validation of combined anthropometric criteria across diverse populations.

These results support the incorporation of WC alongside BMI in obesity screening and encourage further validation of combined anthropometric criteria across diverse populations.