Fat mass and body fat percentage
Fat mass is a weight, usually in kilograms. Body fat percentage puts that amount in relation to total scanned mass. They answer different questions, so it helps to read them together.
Our example uses 18 kg of fat in a total scanned mass of 72 kg. That is 25%. These are made-up values to explain the calculation, not a suggested goal.
Two percentage columns can mean different things
In the report format pictured in STRIVE’s booklet, tissue % fat compares fat with soft tissue mass, while region % fat compares fat with total regional mass, including bone mineral. Always check your own report’s definitions.
Using our invented example: 18 kg fat + 51 kg lean tissue + 3 kg bone mineral = 72 kg total scanned mass.
Fat as a share of total mass is 18 ÷ 72 × 100 = 25.0%. Fat as a share of soft tissue mass is 18 ÷ 69 × 100 ≈ 26.1%. Neither value is a suggested target.
Check the comparison group. Published body composition references vary with age, sex and population. Kelly and colleagues’ NHANES reference study uses US data. It is a reference distribution, not a personalised health target for everyone in Australia. Ask which database your report uses.
Lean tissue is not all muscle
The lean tissue value includes water and organs as well as muscle. If you are following a training programme, it is tempting to read every increase as muscle growth. The scan alone cannot support that conclusion.
Compare the report with your training record and the conditions before each scan. Your practitioner can help decide whether the change is useful. The AIS explains why body composition is only one part of performance.
BMC, lean tissue and lean + BMC
Bone mineral content (BMC) is the amount of mineral measured in a region, usually given in grams. It is not the weight of the whole bone, and it is different from bone mineral density, which is reported per unit area.
A column labelled lean + BMC combines lean soft tissue with bone mineral content. A column labelled lean mass may exclude BMC. Read the column heading before comparing two reports, especially if they came from different systems.
In our example, 51 kg of lean tissue and 3 kg of BMC give 54 kg of lean + BMC. If your report uses grams, 1,000 g equals 1 kg. Discuss bone health findings with your GP.
Android and gynoid regions
Android is an abdominal region. Gynoid is a region around the hips and upper thighs. These labels describe where the scanner’s software has drawn an area for analysis.
When labelled as a fat-percentage ratio, A/G divides android fat percentage by gynoid fat percentage. Check the software’s definition before comparing it with another report. The android region is not the same as visceral fat: an abdominal region also includes fat outside the abdominal cavity.
A ratio below 1 is not presented here as a universal target. Interpretation needs the relevant reference data and your health context. Discuss concerns about abdominal or visceral fat with your GP.
Percentiles, AM and YN
A percentile describes a position within a reference distribution. The 50th percentile is the middle of that distribution. It does not mean that you have 50% body fat or that your health is halfway to a goal.
AM usually means age-matched. YN or YA may identify a young-normal or young-adult comparison. Check the legend: labels and reference groups vary by report. A percentile and a Z-score are different ways of describing a reference comparison, not interchangeable numbers.
A higher percentile is not automatically better. First ask which measurement is being compared, who is in the reference group and whether that comparison is useful for you. The NHANES body composition reference study illustrates why the metric, age, sex and reference population matter.
Appendicular lean mass index
“Appendicular” refers to your arms and legs. ALMI divides their combined lean tissue mass by height squared and is reported in kg/m². Check that your height was recorded correctly.
The index is used in muscle-health assessment, but it does not measure strength. Don’t treat a colour band as a diagnosis. Ask which reference population and clinical criteria were used. See the ISCD body composition positions.
Visceral fat
This is an estimate of fat within the abdominal cavity. Look carefully at the label and units. An area in cm², a volume in cm³ and a weight in grams describe different quantities.
A manufacturer’s coloured scale needs to be read with that system’s documentation. We do not provide a universal cut-off here. Discuss your visceral fat result with your GP, who can put it alongside your health history and other relevant findings. ISCD reporting guidance covers optional body composition measures and their limitations.
Bone mineral density
A body composition report may contain bone measurements, but an osteoporosis assessment uses a dedicated protocol. Check whether your report is for whole-body composition or a diagnostic scan of sites such as the hip and spine.
Discuss bone density results with your GP. Your age, history and reason for testing affect their meaning. Healthdirect’s Australian guide explains diagnostic bone density testing and referrals.
T-scores and Z-scores
A T-score compares bone density with a young-adult reference. A Z-score uses an age-matched reference. They are not percentages.
The ISCD positions apply T-score classification to postmenopausal women and men aged 50 or older. In the appropriate diagnostic setting, a T-score of -2.5 or lower at an accepted site meets the densitometric threshold for osteoporosis. A Z-score of -2.0 or lower is described as below the expected range for age.
Those thresholds do not let this website diagnose you. Discuss the score, scan site and report conclusion with your GP. A whole-body T-score is not interchangeable with a diagnostic hip or spine T-score.
Left and right regions
Read the same measurement on each side. An arm’s fat mass is not comparable with the other arm’s lean tissue mass. Check the region labels before looking at the difference.
If a difference concerns you, ask the practitioner to review positioning and region boundaries. Bring any injury history or symptoms to that conversation. There is no universal “acceptable difference” supplied by this guide.
Sources and how to use them
These links let you check the source material. Reference ranges depend on the population, equipment and reporting method. Clinics in Australia may use different systems.
- ISCD Official Adult Positions, 2023: reporting conventions and diagnostic context.
- Kelly, Wilson and Heymsfield, 2009: body composition references from NHANES.
- Healthdirect: bone density scanning: Australian patient guidance.
- Australian Institute of Sport: DXA best practice: purpose and assessment practice.
STRIVE’s educational booklet
The explanations of report columns, BMC, regional labels and percentiles draw in part on Total Body Composition & Bone Density: Understanding your analysis, supplied by STRIVE Performance Dietetics and credited to Kristof Szanto, Accredited Practising Dietitian (pages 2 to 6 and 10). Adapted with permission.
We have rewritten these explanations for this guide and use invented values in our interactive example. Source attribution does not mean Kristof has reviewed this adaptation. Clinical review is pending.
Sources checked 6 September 2026. This draft has not yet been signed off by a clinical reviewer. Read our editorial policy.
Take your questions to the appointment.
If a label or comparison is unclear, ask the person explaining your scan to point it out on the report. Keep a copy so you can refer to the same measurements next time.
Prepare a few questions ↗