DEXA Scan Body Composition Results: How to Read Every Metric
Introduction: Your DEXA Report Is Only Useful If You Can Read It
Most people who book a DEXA scan already know what it does. The challenge comes after the scan, when the printout arrives packed with acronyms like VAT, ALMI, A/G ratio, and FMI, with almost no plain-language explanation of what any of it means or what to do next.
This guide fixes that. It is a single, scannable reference that translates every key DEXA body composition metric into actionable language. DEXA uses a three-compartment model that separates the body into fat mass, lean (fat-free) mass, and bone mineral content, giving far more granularity than BMI or bioelectrical impedance. For each metric, this article covers the definition, the clinical benchmark, what a result above or below that benchmark means, and when to retest.
The DEXA Report at a Glance: What You’re Actually Looking At
A typical DEXA body composition report has three parts: a whole-body summary table, regional breakdowns (arms, legs, trunk, plus the android and gynoid zones), and a bone mineral density section.
Whole-body analysis is more accurate than segmental analysis. Changes must also exceed the Typical Error of Measurement (TEM) to count as biologically meaningful. In males, body fat TEM sits around 0.44 to 0.66%, so a scan-to-scan shift smaller than that is likely noise, not progress.
The metrics covered here are: Total Body Fat %, Fat Mass Index (FMI), Visceral Adipose Tissue (VAT), Android/Gynoid (A/G) ratio, Appendicular Lean Mass Index (ALMI), Lean Mass Index (LMI), and regional lean mass. One practical point most providers skip: scan standardization (same time of day, hydration status, fasting state, machine, and software) is essential for accurate longitudinal tracking.
Total Body Fat Percentage: The Number Everyone Looks at First
Total body fat percentage is the proportion of total body mass that is fat. Healthy reference ranges run roughly 6 to 25% for men and 20 to 35% for women, though athletic targets differ significantly.
DEXA measures body fat percentage with a margin of error of about 1 to 2%, making it far more reliable than bioelectrical impedance. A real-world study of 1,000 healthy adults found the InBody 770 underestimated fat mass by an average of 3.7 kg in men and 1.9 kg in women versus DEXA, and underestimated body fat percentage by roughly 4.2 percentage points in men.
The practical takeaway: if a gym InBody reads 18% body fat, DEXA may read closer to 22%, which changes training and nutrition decisions meaningfully. This number should never be read in isolation; it should be paired with FMI, VAT, and lean mass for a complete picture.
Fat Mass Index (FMI): Body Fat Adjusted for Height
FMI is total fat mass (kg) divided by height squared (m²). By normalizing for height, it allows more meaningful comparisons across people of different statures than raw body fat percentage alone.
FMI is especially useful for tracking fat loss when body weight is changing significantly. Values above the healthy range correlate with increased cardiometabolic risk independent of BMI. This allows someone to set a precise goal, such as reducing FMI by 1.0 kg/m² over 12 weeks, rather than chasing a scale number. FMI is increasingly used in preventive cardiology and endocrinology as a baseline before and after metabolic interventions.
Visceral Adipose Tissue (VAT): The Metric That Matters Most for Metabolic Health
VAT is the fat stored deep in the abdominal cavity around the organs. It is distinct from subcutaneous fat and far more metabolically active and dangerous.
The clinical risk thresholds are clear: below 100 cm² is low risk; 100 to 160 cm² is moderate risk; and 160 cm² or above is high risk for cardiometabolic disease. Staying below roughly 2 lbs of visceral fat aligns with lower cardiometabolic risk across multiple cohort studies. A dataset of over 450,000 GE iDXA and GE Prodigy scans through May 2025 now enables age- and sex-specific visceral fat percentile benchmarking.
One reliability caveat: VAT has a higher coefficient of variation than other compartments (about 16.2% same-day), so accurate measurement is especially recommended for individuals with a BMI of 25 or above, or VAT mass above 500g PMC. Even modest reductions correlate with measurable improvements in insulin sensitivity and inflammatory markers. If VAT sits in the moderate or high-risk zone, it is the number to prioritize over scale weight.
Android/Gynoid (A/G) Ratio: Where Fat Is Distributed
The android zone covers the upper body, abdomen, and trunk; the gynoid zone covers the hips, thighs, and lower body. The A/G ratio is android fat mass divided by gynoid fat mass. A higher ratio indicates more central (apple-shaped) fat distribution and greater cardiometabolic risk.
Ideal values are generally below 0.8 for women and below 1.0 for men. Because the A/G ratio is independent of total body fat percentage, a lean person can still carry disproportionate android fat and elevated risk. When the ratio is high, fat loss interventions should specifically target central adiposity, which responds well to aerobic exercise and dietary changes. A high A/G ratio and high VAT often appear together and should be read as a combined risk signal.
Appendicular Lean Mass Index (ALMI): A Sarcopenia Risk Score
ALMI is the sum of lean mass in both arms and both legs divided by height squared. It is the primary DEXA metric for diagnosing and monitoring sarcopenia. Clinical cut-offs run approximately 6.35 to 7.0 kg/m² for men and 4.92 to 5.8 kg/m² for women, depending on the reference standard (EWGSOP2, FNIH, or ISCD).
ALMI matters at every age. Low values in the 30s and 40s predict poor functional outcomes decades later, making it a critical longevity metric. The ISCD’s May 2026 DXA Body Composition Analysis course specifically covers sarcopenia and low muscle mass states ISCD, and UVA Radiology notes that ALMI reflects skeletal muscle and is a risk factor for sarcopenia correlated with poor long-term outcomes.
If ALMI approaches the lower threshold, progressive resistance training and adequate protein intake are the two most evidence-supported interventions. Patients on semaglutide or tirzepatide should monitor ALMI closely, as lean mass loss is a documented side effect confirmed in the STEP 1 and SURMOUNT-1 body composition sub-studies.
Lean Mass Index (LMI) and Regional Lean Mass Breakdown
LMI is total lean mass (kg) divided by height squared, a whole-body figure distinct from the limb-focused ALMI. DEXA also reports lean mass separately for the left arm, right arm, left leg, right leg, and trunk, revealing imbalances that total-body metrics hide.
Greater than 10% asymmetry in limb lean mass is flagged as moderate risk, and greater than 15% as high risk for soft-tissue injury. A 2025 Orthopaedic Journal of Sports Medicine scoping review confirmed DEXA as a promising tool for detecting sport-specific adaptations and asymmetry. This makes DEXA particularly valuable for unilateral sport athletes (tennis, baseball, soccer) and those in rehabilitation. A dominant limb showing more than 10% lean mass advantage is a flag for corrective unilateral training. Trunk lean mass is also reported and relevant for functional strength, though it is not part of the ALMI calculation.
Bone Mineral Density (BMD) and Bone Mineral Content (BMC)
A diagnostic bone density scan, ordered by a physician, reports T-scores and Z-scores for osteoporosis screening. A whole-body composition scan includes BMD and BMC data as well. T-score ranges are as follows: normal is above -1.0; osteopenia is -1.0 to -2.5; osteoporosis is -2.5 or below.
Rapid weight loss from GLP-1 medications can reduce bone mineral density, raising the risk of osteopenia, osteoporosis, and fractures, so baseline and follow-up BMD monitoring is important for these patients. DEXA can also detect regional BMD differences, such as higher density in the dominant limb of racket sport athletes. Even when osteoporosis screening is not the primary goal, reviewing BMD trends across serial scans provides an early warning system.
How DEXA Compares to InBody and Other Body Composition Methods
DEXA’s three-compartment model outclasses the two-compartment model most BIA devices use (fat mass versus everything else). The Looney data referenced above illustrates the gap clearly. BIA is also hydration sensitive, deviating by 3 to 5% or more depending on hydration, time of day, and recent food intake, which makes longitudinal tracking unreliable.
DEXA is the only consumer-accessible method that simultaneously measures VAT, ALMI, regional lean mass asymmetry, and BMD in a single session. It is not without limitations: it does not directly measure intramuscular or liver fat, and VAT carries higher variability. For those who want data they can act on with confidence, gym-based BIA results should not drive clinical or performance decisions.
Reading Results in Context: Reference Tables for Key Metrics
| Metric | Benchmark |
|---|---|
| Total Body Fat % | ~6–25% (men); ~20–35% (women) |
| FMI | Above healthy range links to cardiometabolic risk |
| VAT | <100 cm² low; 100–160 cm² moderate; ≥160 cm² high |
| A/G Ratio | <0.8 (women); <1.0 (men) |
| ALMI | Sarcopenia threshold ~6.35–7.0 kg/m² (men); ~4.92–5.8 kg/m² (women) |
| Limb Asymmetry | >10% moderate risk; >15% high risk |
Every value should be interpreted alongside age, training history, and health history; a single metric rarely tells the full story. Population reference values are available in the LEAD cohort normative data. Changes must exceed the Typical Error of Measurement to be meaningful, which prevents overreacting to small fluctuations between scans.
How Often Should You Retest? A Protocol for Every Goal
A single scan is a snapshot; serial scanning reveals directional change. General guidance: every 8 to 16 weeks during active fat loss or muscle building, and every 6 to 12 months for maintenance or longevity tracking.
- GLP-1 patients: Establish a baseline before starting medication, then retest every 8 to 12 weeks to separate fat loss from lean mass loss, a critical distinction as prescriptions have surged in 2026.
- Body recomposition: A 12-week interval allows enough time for detectable simultaneous fat loss and muscle gain, which DEXA uniquely captures.
- Athletes and rehabilitation: Scan at the start of rehabilitation and again before return to sport to confirm limb symmetry has been restored.
- Longevity and maintenance: Annual scans suffice unless a major health or lifestyle change occurs.
For comparability across sessions, time of day, hydration, fasting state, and machine should remain consistent.
Pairing DEXA With Complementary Tests for a Complete Health Picture
An integrated diagnostic stack is an emerging best practice in longevity and performance medicine. DEXA paired with VO2 Max testing combines structural data (body composition) with functional data (cardiovascular fitness), covering two dimensions neither test captures alone. DEXA paired with Resting Metabolic Rate (RMR/REE) testing enables precise caloric targets: knowing both lean mass and actual resting energy expenditure removes the guesswork from nutrition planning.
Blood biomarkers (fasting insulin, CRP, testosterone, and lipid panels) supply the biochemical context that DEXA metrics point toward but cannot measure directly. Belmar Cardiopulmonary Diagnostic Center offers DEXA body composition scanning alongside VO2 Max and Resting Energy Expenditure testing, making it practical to combine multiple assessments in a single appointment. Preventive cardiology protocols and endocrinologists increasingly recommend DEXA as a baseline before and after metabolic interventions, signaling a broader shift away from BMI as the primary health metric.
Conclusion: DEXA Results Are a Roadmap, If You Know How to Read Them
DEXA body composition data is only as useful as the ability to interpret it. With the benchmarks in this guide, every number on a report becomes a specific next step. VAT and ALMI carry the strongest links to long-term health outcomes and should be prioritized first. A single scan is informative, but tracking change over time is where DEXA delivers its greatest value. As BMI continues to lose clinical credibility, DEXA body composition scanning is becoming the baseline standard, and knowing how to read the results is a meaningful advantage.
Ready to Get a Baseline? Book a DEXA Body Composition Scan at BCDC
Readers ready to establish a baseline can book a DEXA body composition scan at Belmar Cardiopulmonary Diagnostic Center in Bellevue, WA. The center offers board-certified physician oversight, same-day results with explanation, and the option to pair DEXA with VO2 Max and REE testing in a single visit. Flexible scheduling, including weekend availability, accommodates busy weekday routines.
To book, call 206-730-9364, email hello@belmarcardio.org, or use the online booking form. The goal is not just data collection but helping every client live a healthier and more intentional life.
