The DEXA Scan: Body Fat, Muscle, and Bone Density Testing
DXA Body Composition Analysis: Fat, Lean Mass & Bone Density Guide
Table of Contents
- What is DXA Body Composition Analysis?
- Understanding Your Body's Three Components
- Key Benefits at a Glance
- What Your DEXA Report Reveals
- Before Your Appointment: Prep & Contraindications
- What to Expect During the Scan
- DEXA vs. Other Body Composition Tests
- Cost, Packages & How to Book
- Real-World Results (Mini Case Study)
- Frequently Asked Questions
- Next Steps
What is DXA Body Composition Analysis?
A dual-energy X-ray absorptiometry (DXA or DEXA) scan provides the most precise analysis of your body composition by measuring three distinct components: fat mass, lean mass, and bone mineral content (BMC). Unlike simple body fat tests, DXA body composition analysis uses advanced X-ray technology to create a complete picture of what your body is actually made of—giving you actionable data for fat loss, muscle building, bone health monitoring, and overall wellness optimization.
This three-compartment model means DEXA doesn't just tell you a single number—it breaks down your entire body into measurable components, showing you exactly where fat and lean muscle are distributed across your arms, legs, and trunk. It can even quantify hard-to-detect visceral adipose tissue (VAT) that surrounds your internal organs and significantly impacts metabolic health.
Why DXA is the Gold Standard for Body Composition Testing
Unlike surface-level tools such as calipers, smart scales, or BMI calculations, DEXA penetrates tissue to reveal what's happening inside your body. Each whole-body scan exposes you to less than 10 µSv of radiation—about the natural background radiation you receive in a single day (IAEA). The actual scan takes just 6–10 minutes of lying still on a padded table (Cleveland Clinic).
Important: BodySpec scans are non-diagnostic wellness tests. While your report includes bone-density metrics (BMD, T-score, Z-score) that can flag the potential for osteopenia or osteoporosis, only a physician-ordered diagnostic DEXA scan can confirm or rule out those conditions. If your BodySpec results show unusually low bone density, share them with your healthcare provider.
For more details on safety, read our article: Radiation, DEXA Scans, and You.
Understanding Your Body's Three Components
DXA body composition analysis is based on a three-compartment model that separates your body into its fundamental building blocks. Here's what each component means and why it matters:
1. Fat Mass (FM)
Fat mass is the total weight of all lipids (triglycerides and phospholipid membranes) in your body, measured in kilograms or pounds. This includes both subcutaneous fat (under your skin) and visceral fat (around your organs).
Key metric: Total Body Fat Percentage—the proportion of your body composed of fat tissue. This number changes based on both how much fat you have and how much lean mass you carry.
Key metric: Fat Mass Index (FMI)—your total fat mass relative to your height (Fat Mass / Height²). Unlike BMI, FMI is independent of lean mass, making it a more accurate indicator of obesity status. Research suggests healthy ranges are typically 5-9 kg/m² for women and 3-6 kg/m² for men.
Key metric: Visceral Adipose Tissue (VAT)—the amount of fat surrounding your internal organs, measured in grams or cm². Research shows VAT levels exceeding 100-110 cm² are associated with increased metabolic risk, while levels above 160 cm² indicate high metabolic risk for cardiovascular disease, diabetes, and liver conditions.
2. Lean Mass (LM)
Lean mass represents all lipid-free soft tissue in your body—primarily skeletal muscle, but also organs, skin, body water, connective tissue, and soft tissue minerals. This is often called "fat-free mass" and makes up approximately 50-60% water.
Key metric: Total Lean Mass—measured in kilograms or pounds for your whole body and individual regions (arms, legs, trunk). Tracking changes in lean mass helps confirm whether your training and nutrition plan is actually building muscle or if you're losing muscle during weight loss.
Key metric: Appendicular Lean Mass Index (ALMI)—the amount of lean tissue in your arms and legs relative to your height (Appendicular Lean Mass / Height²). This metric is crucial for screening sarcopenia (age-related muscle loss) and assessing athletic performance. Research cutpoints are generally around 7.0 kg/m² for men and 5.5 kg/m² for women.
Key metric: Appendicular Lean Mass to BMI Ratio (ALM/BMI)—particularly useful for overweight individuals, with research cutpoints around 0.79 for men and 0.51 for women as indicators of potential sarcopenia risk.
3. Bone Mineral Content (BMC)
Bone mineral content is the actual weight of minerals (primarily calcium and phosphorus) in your skeleton, measured in grams. This is different from bone mineral density (BMD)—BMC tells you how much bone you have, while BMD tells you how dense that bone is.
How BMC is measured: BMC is calculated directly from the X-ray attenuation properties of bone tissue. For your whole body, it typically ranges from 2,000-3,500 grams depending on your size, sex, and bone structure. Learn more about bone weight.
Why BMC matters: While BMC alone doesn't diagnose osteoporosis (that requires BMD and clinical assessment), tracking BMC changes over time helps monitor the effects of strength training, nutrition changes, hormonal shifts, or aging on your skeletal system.
BMC vs. BMD: Bone mineral density is derived by dividing BMC by the scanned bone area (BMD = BMC / Area), expressed as g/cm². Two people can have the same BMC but different BMD—for example, a shorter person will typically have higher BMD than a taller person with identical BMC.
Key Benefits at a Glance
| Goal | How DEXA Body Composition Analysis Helps | Why It Matters |
|---|---|---|
| Lose body fat | Pinpoints total fat mass, body fat %, FMI, and VAT in grams/cm² | Hidden visceral fat significantly increases cardiometabolic risk. Tracking FMI is more accurate than BMI for obesity assessment. |
| Build muscle | Tracks lean mass changes in arms, legs & trunk; provides ALMI data | Confirms if training & protein plan are adding muscle—not just scale weight. ALMI helps identify muscle imbalances. |
| Bone health (non-diagnostic) | Measures bone mineral content (BMC) in grams and bone mineral density (BMD) with T-scores & Z-scores | Low BMD can indicate risk for osteopenia/osteoporosis—bring results to your doctor for diagnostic testing. BMC tracking shows skeletal response to training. |
| Rehab / performance | Flags asymmetries between left/right limbs in lean mass and bone density | Guides physiotherapy & sport-specific training. Identifies potential injury risk from imbalances. |
| Body composition research | ±0.5 % error for fat & lean mass at BodySpec thanks to rigorous QA procedures (DXA standard: ±1%) | FDA-cleared technology with BodySpec's enhanced precision—consistent across all storefront and mobile locations. |
| Weight management | Estimates Resting Metabolic Rate (RMR) based on tissue composition | RMR calculation from lean mass and fat mass helps create accurate calorie targets for fat loss or muscle gain. |
In summary, DXA body composition testing offers:
- Precision: BodySpec achieves ±0.5 % error through rigorous QA procedures—more precise than the standard ±1% DXA accuracy and far superior to the 5–9 % error of most consumer bio-impedance devices (Weightology). This consistency applies whether you scan at a storefront or mobile van location.
- Comprehensiveness: Full-body and regional breakdown—including android (belly) and gynoid (hips) zones
- Three-compartment analysis: Fat mass, lean mass, AND bone mineral content in one 10-minute scan
- Actionability: Repeat every 8–12 weeks to verify if diet or training tweaks are working (Learn when to scan)
What Your DEXA Report Reveals
Understanding what you'll receive after your DXA body composition scan helps you maximize the value of your results:
Regional Body Composition Breakdown
Your report divides your body into specific regions with fat mass, lean mass, and BMC measurements for each:
- Arms (left and right): Track muscle development or imbalances from sports/training
- Legs (left and right): Monitor lower body lean mass and identify asymmetries
- Trunk: Includes android (abdominal) and gynoid (hip) regions
- Head: Typically excluded from body composition analysis
Android vs. Gynoid Fat Distribution
The android region represents fat stored around your midsection (the "apple" shape), while the gynoid region represents fat around your hips and thighs (the "pear" shape). Your android-to-gynoid (A/G) ratio indicates where your body preferentially stores fat:
- Women: Ideal A/G ratio < 0.8
- Men: Ideal A/G ratio < 1.0
Higher android fat (abdominal obesity) is associated with greater metabolic risk than gynoid fat storage.
Body Composition Indices
- Total Body Fat %: Percentage of your body composed of fat tissue
- FMI (Fat Mass Index): Total fat relative to height—better than BMI for obesity classification
- ALMI (Appendicular Lean Mass Index): Arm and leg muscle relative to height—key for sarcopenia screening
- ALM/BMI Ratio: Muscle-to-BMI ratio, especially useful for overweight individuals
Bone Health Metrics (Non-Diagnostic)
- Total BMC: Weight of all minerals in your skeleton (grams)
- Whole-Body BMD: Average bone mineral density across your skeleton (g/cm²)
- T-Score: Compares your BMD to a healthy 30-year-old (above -1.0 is normal)
- Z-Score: Compares your BMD to people your same age, sex, and ethnicity
Metabolic Estimates
Resting Metabolic Rate (RMR): Your DEXA scan estimates the number of calories your body needs at rest based on your lean mass and fat mass composition. This provides a more accurate baseline than standard RMR calculators that only use age, height, and weight. Think of this as your "ideal" RMR given your specific body composition.
Before Your Appointment: Prep & Contraindications
48 Hours Prior
- Unless prescribed by your doctor, pause high-dose calcium or iron supplements (those exceeding 100 % of the Recommended Daily Allowance); they can artificially elevate BMD readings
24 Hours Prior
- Skip any barium or contrast imaging
- Ease up on very salty meals; large fluid shifts can slightly affect lean mass measurements
Day Of
- Eat a light meal or fast two hours beforehand
- Wear athletic clothes with no metal zippers or buttons; sports bras without underwire are fine
- Remove jewelry, smart watches, and fitness trackers
Who Should Reschedule?
- Pregnant individuals
- Anyone who has had contrast imaging in the last 24 hours
For additional pro tips check out 5 Tips for a Successful BodySpec Scan.
What to Expect During the Scan
- Check-in & Consent (≈ 5 min). A certified BodySpec tech reviews your body composition goals and confirms there's no pregnancy risk.
- Positioning (≈ 1 min). You lie supine; foam blocks support your feet to keep hips neutral.
- Imaging (6–10 min). A scanning arm glides overhead; you don't enter a tunnel. Relax and breathe normally while the DXA measures your fat mass, lean mass, and bone mineral content.
- Quick Results: BodySpec sends your PDF report digitally after your appointment. Our 24/7 AI agent is available right in your dashboard to explain your body composition metrics—including fat mass, lean mass, BMC, and all regional breakdowns—at any time.
Total time in-office: about 10–15 minutes.
DEXA vs. Other Body Composition Tests
| Metric | DEXA | BodPod (Air) | Bio-Impedance (BIA scale) | Skinfold Calipers | Hydrostatic Weighing | BMI (Body Mass Index) |
|---|---|---|---|---|---|---|
| Typical %-Error | ±0.5 % at BodySpec (standard DXA: ±1%) | ±1–3 % (Fields 2002) | ±3–8 % (Sun 2005) | ±3–5 % (UC Davis) | ±1.8–2.8 % (Healthline) | Highly variable; misclassifies up to 50 % of active adults (BMI vs. body fat percentage) |
| Measures VAT | Yes | No | Estimate only | No | No | No |
| Segmental Data | Arms, legs, trunk | Whole body only | Some devices | No | No | No |
| Bone Density (BMC/BMD) | Yes | No | No | No | No | No |
| Lean Mass Indices (ALMI) | Yes | No | No | No | No | No |
| Test Time | 6–10 min | 5–8 min | 30 sec | 5 min | 15–20 min | Seconds |
| Comfort | Lie still | Sit in small pod | Stand on metal plates | Pinch skin | Hold breath underwater | N/A—just height & weight |
| Ideal For | Complete body composition analysis | General fitness | Home tracking | Quick gym checks | Research labs | Population screening |
Want a deeper dive? Check out BodySpec DEXA vs. Other Body Composition Tests and learn more about The DEXA Scan: Body Fat, Muscle, and Bone Density Testing.
Cost, Packages & How to Book
BodySpec keeps pricing simple and transparent nationwide. Choose the plan that matches your body composition tracking goals:
| Package | Scans Included | Price | Payment Frequency |
|---|---|---|---|
| Monthly (Best Value) | 1 scan/month | $39.95 | Billed monthly |
| Monthly Plus | 2 scans/month | $69.95 | Billed monthly |
| Quarterly (Most Popular) | 1 scan/quarter | $49.95 | Billed every 3 months |
| Quarterly Plus | 2 scans/quarter | $79.95 | Billed every 3 months |
| One-Time Baseline | 1 scan | $59.95 | One-off |
Prices are subject to change—please check the booking portal for the most current rates. Credits never expire and can be shared with friends or family.
Insurance rarely covers body composition testing because these scans are considered wellness services, but most FSA/HSA cards are accepted.
Booking in Two Clicks
- Visit our online scheduling page.
- Choose your nearest location—mobile vans or clinics—and pick a 20-minute slot.
For a deeper dive on budgeting your scans, see How Much Does a DEXA Scan Cost?.
Real-World Results (Mini Case Study)
Lisa B. – Weight-Loss Client, Mid-40s (16 Weeks)
- Starting stats: 35 % body fat
- Interventions: Walking daily; 11 weeks of weight lifting with a trainer
- Outcome: Reduced body fat by 14 percentage points, achieving 21 % body fat while maintaining lean mass
"I would not have known about the need for weight lifting, and building lean tissue, without BodySpec. That was a lightbulb moment for me."
Lisa's DEXA body composition scans revealed that her lean mass stayed stable while her fat mass decreased—proving her training program was working optimally. This data confirmed she was losing fat, not muscle.
Read the full story: BodySpec Client Stories: Lisa B..
Frequently Asked Questions
How often should I get a DXA body composition scan? Every 8–12 weeks gives enough time for measurable changes in fat mass and lean mass without wasting money. For bone density monitoring (non-diagnostic), annual scans are typically sufficient.
Will hydration affect my lean mass results? Slightly—DEXA assumes lean tissue is 73% water. Large hydration shifts can affect lean mass measurements by about 1% for every 5% change in hydration. That said, DEXA is much less sensitive to hydration than bioimpedance (BIA) devices. Aim for normal hydration and avoid large meals within two hours.
Is it safe if I have metal implants? Yes. Hip or knee hardware shows up on the image but doesn't affect safety; BMC and BMD results for that limb may be flagged but the scan is still valuable for tracking fat mass and lean mass changes.
Can kids get DXA body composition scans? Children under 18 need guardian consent. Pediatric reference charts differ from adult norms, so discuss goals with the tech first.
What about radiation buildup from repeat scans? Each whole-body DEXA is under 10 µSv (IAEA). Ten scans therefore total about 100 µSv—roughly equivalent to the dose from a single adult chest X-ray (RadiologyInfo).
What's the difference between BMC and BMD? BMC (bone mineral content) is the total weight of minerals in your bones, measured in grams. BMD (bone mineral density) is BMC divided by the bone area, measured in g/cm². BMD is used for osteoporosis screening, while BMC helps track skeletal changes over time.
Does DEXA measure actual muscle or just lean mass? DEXA measures total lean mass, which includes skeletal muscle, organs, connective tissue, and body water. It cannot separate pure muscle tissue from other lean components. However, regional lean mass measurements (especially appendicular lean mass in arms and legs) serve as reliable proxies for skeletal muscle mass.
Next Steps
Book your BodySpec DXA body composition analysis today and get precise measurements of your fat mass, lean mass, and bone mineral content—all in one 10-minute scan. Turn that data into measurable progress toward your fitness, health, and performance goals.
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