A DEXA report hands you forty numbers and no instructions. Most people read one of them, body fat percent, and argue with it. The useful parts are further down the page.
Here is the order I read one in, what each number can tell you, and what it cannot. Nothing here is a diagnosis. A report is a measurement. What it means for you is a clinician conversation.
Start With The Three Masses
Every body composition report splits your weight three ways: fat mass, lean mass, and bone mineral content. Body fat percent is just fat mass divided by the total. The body that sets DEXA standards says every report should show total mass, fat mass, lean mass, percent fat, bone mineral content, and bone density.
One correction most people need. Lean mass is not muscle. It is everything that is not fat or bone, which means muscle, organs, and water. Drink a lot before the scan and lean mass goes up. That matters later, when you compare two scans.
Body Fat Percent Has No Official Pass Mark
This surprises people. The standards body says it plainly: specific thresholds to define obesity by body fat have not been established. The colored bands on your report come from the scanner maker or the clinic.
What the report usually does have is a percentile. That compares you to a reference population of the same age and sex, built from a large US health survey. Read it carefully. In that data, body fat keeps rising until about age 80 in men and 65 in women. So the fiftieth percentile at 55 is a comparison with people who have been gaining fat for decades. Average is not the same as fine.
Where The Fat Sits
The regional table breaks fat down by arms, legs, and trunk. Two regions get their own names. Android is the waist. Gynoid is the hips and upper thighs. The android to gynoid ratio compares them. A higher ratio means more of your fat is carried centrally.
There is no official cutoff for that ratio either. Treat it as a direction, not a grade. If it falls between scans while total fat falls, the fat is coming off the place that matters most.
Visceral Fat Is The Number Worth Finding
Visceral fat is the fat packed around your organs. Newer scanners estimate it, and the estimate holds up. In a validation study of 124 adults, the DEXA figure tracked a CT scan closely.
Check the unit before you compare anything. Depending on the scanner, visceral fat is reported as an area, a mass, or a volume. Those are not interchangeable, and a number from one machine does not transfer to another. I wrote more about why this one matters in what visceral fat measures.
The Lean Mass Indexes
Near the bottom you may see lean mass divided by height squared, and a second version that counts only arms and legs. The arms and legs version is called appendicular lean mass index, or ALMI. It is the closest thing on the page to a muscle number, because it leaves the organs out.
A European consensus group uses ALMI to screen older adults for low muscle. Its lines are below 7.0 kilograms per square meter for men and below 5.5 for women. Those are screening lines for sarcopenia, and the authors call some of their own cutoffs arbitrary. They are a floor to stay well above, not a target to aim at.
| Number on the report | What it tells you | What it cannot tell you |
|---|---|---|
| Body fat percent | Share of your weight that is fat | Whether that is healthy. No official line exists |
| Lean mass | Everything that is not fat or bone | Muscle alone. Water moves it |
| Visceral fat | Fat around the organs | Anything across machines or units |
| Android to gynoid ratio | How central your fat is | A pass or fail. It is a direction |
| ALMI | Arm and leg lean mass for your height | Strength. Lift something to learn that |
| Total body bone density | A rough read on bone | Whether you have osteoporosis |
Bone Density Is A Different Test
A whole-body scan prints a bone density figure, and sometimes a T-score. Do not read it as a bone health verdict. Osteoporosis is diagnosed from dedicated scans of the lower spine and hip. If bone is the question, ask for that test.
How Much Change Is Real
This is where most misreadings happen. The accepted precision for a well-run scan is about 3 percent for fat mass and 2 percent for lean mass and percent fat. A change smaller than that may be the machine, not you.
The fix is boring. Use the same machine. Scan in the same state each time: fasted, same time of day, same clothing, empty bladder, no hard workout right before. Hydration alone can move lean mass. One scan is a snapshot. Two scans done the same way are a trend.
This matters most when weight is coming off fast. If you are on a GLP-1, the question is not how much you lost. It is how much of it was lean. That is its own piece: how to track lean mass on a GLP-1.
What I Built Mallet To Do With The Report
A PDF in a folder is not tracking. Mallet reads an uploaded DEXA report and pulls out the numbers above: fat and lean mass, visceral fat, the regional split, and the lean mass indexes. Then it puts them next to protein, lifting, and labs. I want the second scan to answer a question the first one raised.
Upload the report. Mallet keeps fat, lean mass, and visceral fat on one timeline with your food and training, so the next scan shows what changed and why. Get early access →
This Week
Open your last report and write down three numbers: fat mass, lean mass, and visceral fat, with the unit. Then write down the machine and how you prepared. That note is what makes the next scan worth paying for. If you have not picked a way to keep scans over time, I compared the options in the best DEXA scan tracking apps.
Selected References
- International Society for Clinical Densitometry. Adult Official Positions. Body composition reporting, precision, and thresholds.
- Kelly TL, et al. Dual energy X-ray absorptiometry body composition reference values from NHANES. PLoS One. 2009.
- Kaul S, et al. Dual-energy X-ray absorptiometry for quantification of visceral fat. Obesity. 2012.
- Cruz-Jentoft AJ, et al. Sarcopenia: revised European consensus on definition and diagnosis. Age and Ageing. 2019.
This article is for education, not medical advice. A DEXA report is a measurement, not a diagnosis. Take questions about bone density, body composition, or weight loss to a clinician.