Body composition analysis (Lunar iDXA)
Clinical-grade scan for fat, muscle, and bone analysis — the gold standard for precise body composition and metabolic health tracking
Table of contents
Basic data
Dual-energy X-ray absorptiometry (DXA) with the GE Lunar iDXA scanner is a highly precise diagnostic used to assess body composition — including total and regional fat mass, lean tissue, and bone mineral density. It’s considered the gold standard in both research and clinical settings for evaluating body composition and bone health.
Compared to BIA or skinfold methods, DXA provides much more accurate and detailed measurements. It allows for early detection of visceral fat accumulation, osteoporosis risk, or muscle loss — making it invaluable for longevity, performance, and metabolic health tracking.
Category: Body composition
Level: Intermediate
Usefulness: High
Level
Intermediate
This test is classified as Intermediate because while it provides extremely valuable insights, it typically requires access to a clinical setting, incurs higher cost, and may not be needed in the very early stages of a health journey. However, once basic health habits are in place, it becomes an excellent tool for refining protocols with precise data.
Ideal for users focused on performance, fat loss, muscle gain, or healthy aging, DXA enables data-driven decisions and early risk detection (especially for visceral fat and bone loss). Its high precision supports advanced goal setting and fine-tuning of nutrition and training protocols.
Usefulness
High
Precise measurement of visceral and subcutaneous fat
Unlike BIA or calipers, DXA directly distinguishes between visceral and subcutaneous fat — helping identify metabolic risks not visible through BMI or appearance.
Regional fat distribution mapping
DXA provides detailed visual and quantitative data on how fat is distributed across body regions — arms, legs, trunk, and abdominal (android/gynoid) zones. This helps identify asymmetries and track local changes in fat loss or muscle gain.
Gold-standard lean mass tracking
DXA enables extremely accurate monitoring of muscle gain or loss, ideal for athletic performance, recomposition, or aging-related sarcopenia prevention.
Bone mineral density assessment
Simultaneously measures BMD, allowing early detection of osteopenia or osteoporosis — a key component of healthy aging.
How it works
Dual-energy X-ray scanning
The machine emits X-rays at two energy levels. Tissues like fat, muscle, and bone absorb these beams differently, allowing precise tissue differentiation.
Tissue mapping and segmentation
The scan produces a detailed image of the entire body, segmented by region (arms, legs, trunk) and tissue type (lean, fat, bone).
Quantitative analysis via software
Specialized software calculates total and regional mass of each tissue type and compares values to reference populations for age, sex, and body type.
Measures
Visceral Adipose Tissue (VAT)
Accurately quantifies deep abdominal fat linked to insulin resistance, inflammation, and cardiometabolic risk — difficult to assess via most other methods.
Total & regional body fat percentage
Assesses overall fat levels and distribution — including arms, legs, trunk — supporting nuanced recomposition planning.
Fat distribution heatmap
Provides a visual, color-coded map showing how fat is distributed across different body regions. Helps identify localized fat accumulation and monitor regional changes over time.
Lean mass (total and segmental)
Tracks muscle mass in limbs and trunk. Key for strength, mobility, and aging resilience.
Bone Mineral Density (BMD)
Identifies risks for osteopenia or osteoporosis. Critical for aging adults, women, and those with low body weight.
Fat Mass Index (FMI) and Lean Mass Index (LMI)
Adjusts fat and lean tissue values for height — offering more accurate insights than BMI.
Android/Gynoid Ratio
Compares fat storage patterns — useful in evaluating hormonal influences and cardiometabolic risk.
Reliability
Extremely high repeatability
Minimal variability between scans under similar conditions. Reliable enough to detect small changes in fat or lean mass.
Standardized reference ranges
Offers comparisons to validated population norms by age, sex, and ethnicity — enhancing interpretability.
Requires immobility and calibration
The subject must lie still for best accuracy. Device calibration and operator skill also affect precision.
Limitations
Limited availability
Requires specialized equipment and trained technicians, usually available only in clinics or hospitals.
Higher cost than other methods
Typically costs more than BIA or caliper testing, though prices are falling with wider adoption.
Exposure to low-dose radiation
Not recommended for frequent scanning in short intervals. Not suitable for pregnant individuals.
Not portable or home-usable
Cannot be self-administered — scans must be scheduled in advance at a diagnostic center.
Frequency
General health and longevity tracking
Once per year is sufficient for most users to assess long-term trends in fat distribution, lean mass preservation, and bone density. Ideal as an annual check-in for body composition and skeletal health.
During significant recomposition or medical treatment
Every 3–6 months may be appropriate when actively working on fat loss, sarcopenia prevention, or osteoporosis treatment. Always interpret in the context of medical guidance or lifestyle interventions.
Cost
Clinical centers and hospitals
Typically $80–200 per session, depending on region and whether bone scan or full body composition is included.
Sports labs and wellness clinics
Many high-performance or longevity clinics offer DXA scans as part of premium diagnostics packages or a la carte ($100–150 typical).
Availability
Diagnostic centers and hospitals
Available at radiology departments, metabolic clinics, and university research centers.
Private performance and health clinics
Often integrated into advanced health assessments, athlete evaluations, or bio-optimization programs.
Preparation
No food or training prior
Avoid eating, drinking, or training 2–4 hours before scan. Remove jewelry and wear light clothing or gown.
Hydration and rest
Maintain normal hydration but avoid overhydration. Arrive rested to avoid fluid shifts.
Interpretation
Monitor changes in visceral fat and lean mass
These are the most informative for metabolic health and aging. Even small improvements are meaningful.
Compare to population reference ranges
Use Z-scores and percentiles to assess whether values fall within healthy ranges for your age and sex.
Focus on trend, not perfection
Recomposition is gradual. Look for sustained movement in fat reduction, muscle gain, and bone density improvements.
Alternatives
BIA (e.g., Tanita or InBody)
More accessible and affordable but less precise — good for regular tracking when DXA isn’t available.
Skinfold calipers
Inexpensive and mobile but requires experience to use correctly. Doesn’t measure visceral fat or bone.
FAQ
Is DXA safe for repeated use?
Yes — the radiation dose is extremely low, similar to a few hours of natural background radiation. However, it's not advised to do it very frequently.
Can DXA detect bone loss early?
Yes — BMD readings help detect osteopenia or osteoporosis before symptoms occur.
Is the scan uncomfortable?
Not at all. You lie flat for a few minutes while the scanner moves above you. No injections or contact.
Can athletes benefit from DXA?
Absolutely. DXA is ideal for athletes tracking body fat, muscle symmetry, and bone density over time.
How do I access a DXA scan?
Search for local sports medicine clinics, radiology departments, or longevity-focused wellness centers. Many offer one-off bookings.