DEXA Scan (Body Composition & Bone Density) — Diagnostics & Biomarker Testing
Dual-energy X-ray absorptiometry providing precise lean mass, fat mass, visceral fat, and bone mineral density measurements — the gold standard for sarcopenia and osteoporosis assessment.
Overview
DEXA (Dual-Energy X-ray Absorptiometry) uses two X-ray beams at different energy levels to distinguish bone mineral, lean tissue, and fat tissue across the entire body. It is the gold standard for measuring body composition with high precision (< 1% coefficient of variation for lean mass). DEXA uniquely quantifies visceral adipose tissue (VAT) — the metabolically active fat surrounding abdominal organs that drives cardiovascular risk, insulin resistance, and inflammation — separately from subcutaneous fat. It also identifies appendicular skeletal muscle mass (ASM), the basis for sarcopenia diagnosis. Peter Attia, Bryan Johnson, and virtually all longevity practitioners use DEXA as a cornerstone of monitoring. T-score (bone density relative to young healthy adults) diagnoses osteopenia (T-score -1.0 to -2.5) and osteoporosis (T-score ≤ -2.5). Radiation dose is extremely low (~0.001 mSv, less than a day's background radiation).
Indications
- Sarcopenia diagnosis and muscle mass tracking
- Osteoporosis and osteopenia screening
- Visceral adipose tissue quantification
- Body composition response to diet and exercise interventions
- Hormonal deficiency assessment (testosterone, estrogen, growth hormone effects on body composition)
Mechanism of Action
Two X-ray beams at different photon energies are differentially attenuated by bone mineral versus soft tissue, allowing algorithmic separation of three tissue types: bone, lean, and fat
Dosing
| Compound | Dose | Frequency | Notes |
|---|---|---|---|
| DEXA Scan | 10-20 min full-body scan | Every 6-12 months | Cost: $50-200 cash-pay; bone density scan often insurance-covered for osteoporosis indications |
Evidence Grade
GRADE A
Safety & Contraindications
- Minimal ionizing radiation (~0.001 mSv) — extremely safe for repeated use
- Avoid if pregnant
- Results vary slightly by machine manufacturer (Hologic vs. GE) — compare results from same machine for longitudinal tracking
- DEXA measures mass, not function — combine with strength testing and functional assessments