DEXA Scan: The Complete Guide

What Is a DEXA Scan?

DEXA (Dual-Energy X-ray Absorptiometry) was originally developed to measure bone density for osteoporosis diagnosis. But the same technology that sees through bone also precisely measures body composition—making it the gold standard for tracking fat loss and muscle gain.

Think of it as an X-ray that can distinguish between bone, muscle, and fat tissue in every region of your body.

What DEXA Actually Measures

Why DEXA Beats Everything Else

Who Should Get a DEXA Scan?

Essential For:

• Serious fitness enthusiasts - Track if you're actually building muscle or just gaining weight
• Anyone losing weight - Ensure you're losing fat, not muscle
• Athletes - Optimize body composition for performance
• People on GLP-1s or TRT - Monitor muscle preservation during weight loss
• Post-menopausal women - Bone density screening for osteoporosis

Helpful But Optional For:

• Anyone curious about their real body composition
• Those frustrated that scale weight doesn't reflect how they look/feel
• People wanting baseline data before making changes

What Your Results Tell You

Here's how to interpret your scan:

Body Fat Percentage Ranges

Visceral Fat: The One That Matters Most

Visceral fat (fat around organs) is far more dangerous than subcutaneous fat (under skin). DEXA quantifies this separately.

• 0-100 cm²: Low risk
• 100-160 cm²: Moderate risk—focus on reducing
• 160+ cm²: High risk for metabolic disease, cardiovascular issues

How Often Should You Scan?

This depends on your goals and what you're tracking:

• Quarterly (every 3 months): Ideal for active body recomposition goals
• Bi-annually: Good for general tracking if maintaining weight
• Monthly: Usually overkill—body comp doesn't change that fast

Cost & Where to Get Scanned

How to Prepare for Your Scan

• Wear comfortable clothing without metal (zippers, bras with underwire, etc.)
• Remove all jewelry and accessories
• Hydrate normally—no special preparation needed
• Fast for 2-3 hours before (optional, but reduces variability)
• Avoid heavy workouts same-day (can affect hydration/glycogen)
• Scan at same time of day for consistent tracking

Real-World Use Cases

Example 1: Weight Loss Done Right

Sarah lost 30 lbs in 6 months. Her scale said success, but her DEXA revealed she lost 25 lbs of fat and 5 lbs of muscle. Adjusted to add more protein and strength training. Next scan 3 months later: 15 lbs fat lost, 2 lbs muscle gained. Real progress.

Example 2: Recomposition

Mike's scale weight stayed the same for 4 months (frustrating!). His DEXA showed he lost 8 lbs of fat and gained 8 lbs of muscle. Same weight, completely different body. This is why the scale lies.

Example 3: GLP-1 Monitoring

On semaglutide, Jennifer lost 40 lbs. Without adequate protein, her DEXA showed 30 lbs fat + 10 lbs muscle lost. She increased protein to 100g/day and added resistance training. Next 20 lbs lost: 19 lbs fat, 1 lb muscle. Much better ratio.

Why BMI Is Useless (And DEXA Isn't)

BMI (Body Mass Index) is a ratio of height to weight. It can't tell the difference between a bodybuilder and someone with high body fat at the same weight. Examples:

• 6'0" male at 200 lbs = BMI 27 ("overweight") - could be 12% body fat athlete or 30% sedentary
• 5'4" woman at 140 lbs = BMI 24 ("normal") - could be 35% body fat or 20% fitness enthusiast

DEXA solves this by showing your actual tissue composition. Two people with identical BMI can have 15%+ difference in body fat percentage.

The Bottom Line

At $40-45/scan, DEXA is the single best investment for anyone serious about fitness or health optimization. It's the only way to know if your diet and training are actually working, or if you're just spinning your wheels.

Recommended frequency: Get a baseline scan, then retest every 3 months if actively trying to change body composition. Once you're maintaining, twice a year is enough.