From the Guidelines
A DEXA scan for body composition analysis provides several key metrics including bone mineral density (BMD), bone mineral content (BMC), lean mass, fat mass, and percent body fat, as well as regional assessments and calculations of android and gynoid fat distribution, visceral adipose tissue (VAT) measurements, fat mass index (FMI), and lean mass index (LMI) 1. The scan divides these measurements into regional assessments, showing composition data for the trunk, arms, legs, and total body.
- Key metrics provided by a DEXA scan include:
- Bone mineral density (BMD)
- Bone mineral content (BMC)
- Lean mass
- Fat mass
- Percent body fat
- Android (abdominal) and gynoid (hip/thigh) fat distribution
- Visceral adipose tissue (VAT) measurements
- Fat mass index (FMI)
- Lean mass index (LMI) These metrics are important for assessing health risks, monitoring changes from diet or exercise interventions, and evaluating sarcopenia or obesity 1. DEXA is considered the gold standard for body composition analysis because it uses two different energy X-ray beams that can differentiate between bone, lean tissue, and fat based on their different absorption rates, providing more accurate and comprehensive body composition data than methods like bioelectrical impedance or skinfold measurements 1. The most recent guidelines for DEXA scans recommend that total body values of BMI, BMD, BMC, total mass, total lean mass, total fat mass, and percent fat mass should appear on all reports, and that DEXA measures of adiposity and lean mass include visceral adipose tissue (VAT), appendicular lean mass index (ALMI), android/gynoid percent fat mass ratio, trunk to leg fat mass ratio, lean mass index (LMI), and fat mass index (FMI) 1.
From the Research
Metrics Provided by DEXA Scan
The following metrics are provided by a Dual-Energy X-ray Absorptiometry (DEXA) scan for body composition analysis:
- Fat mass
- Lean mass
- Bone mineral mass
- Percent fat in soft tissue (% Fat)
- Fat percentage
- Lean body mass
- Bone mineral density (BMD)
- Regional body composition, including:
- Arm tissue mass
- Leg tissue mass
- Trunk tissue mass
- Regional bone mineral content and density
Precision and Accuracy of DEXA Measurements
Studies have shown that DEXA measurements have high precision and accuracy, with precision errors of:
- 1.1 kg (6.4%) for fat mass 2
- 1.6% (5.7%) for fat percentage 2
- 1.4 kg (3.1%) for lean tissue mass 2
- 0.03 kg (1.2%) for total body bone mineral 2
- 0.8% for total body BMD and 1.5% for lean body mass 3
Clinical Applications of DEXA
DEXA scans have various clinical applications, including: