How to read your DEXA scan results, line by line

A DEXA report is two or three dense pages of numbers with no narrator. This is the walkthrough I wanted the first time I held one: what each line of the body-composition section means, which numbers deserve attention, and which are noise.

The headline: total body fat %

Usually top of page one: your whole-body fat mass divided by total mass. Two things to know:

1. DEXA's percentage runs higher than field methods. It measures essentially all fat in the body — including fat marbled through organs and muscle that calipers and bioimpedance devices don't capture. Don't panic when DEXA reads 4-6 points above your gym's InBody; the reference data below is DEXA-measured too, so you're compared apples-to-apples.
2. Context requires age and sex. The published NHANES percentile curves move substantially across adulthood — the chart guide has the full tables, and the interpreter computes your exact percentile.

Fat mass and lean mass, in mass units

Below the percentage you'll find fat mass and lean mass (sometimes "lean + BMC"). Track these in kg or lb, not just the percentage: if you gain 2 kg of muscle at constant fat, your fat percentage drops — the percentage confounds two changes the masses keep separate. Progress between scans is best read as Δfat-mass and Δlean-mass.

The regional table: arms, legs, trunk

Every report breaks composition down by region. The gold in this table is appendicular lean mass (ALM) — the lean mass of both arms plus both legs, which is mostly skeletal muscle. Divide by height squared and you get ALMI, the index used across the research literature on low muscle mass; the interpreter computes it and shows your percentile against the NHANES reference curves.

Visceral fat (VAT)

Modern DEXA software estimates the fat surrounding your abdominal organs, reported as an area (cm²), mass (g), and/or volume (cm³). It's the report's most health-relevant fat number: research thresholds treat ~100 cm² as elevated visceral adiposity. The visceral-fat guide covers what the number means and the lifestyle levers with actual evidence behind them.

A/G ratio and the colored image

The android/gynoid ratio compares trunk-pattern fat to hip/thigh-pattern fat (see FAQ below). The body image with tissue coloring is a visualization of the same regional data — useful for spotting asymmetries (a rehabbed leg lagging its pair), not a diagnostic picture.

What to ignore

• Tiny scan-to-scan wobbles. Repeat-scan precision is real but finite; hydration and gut contents move the numbers. Our accuracy guide covers how much change is meaningful.
• Cross-machine comparisons. Hologic and GE Lunar machines partition tissue slightly differently. Compare your scan to your previous scan on the same machine — that's also why retest cadence and consistency matter more than scan frequency.
• Anyone else's numbers. Percentiles exist so you don't have to benchmark against a fitness influencer's screenshot.

Every reference table and formula behind the interpreter is documented, with primary sources, on the methodology page.