A useful report conversation starts with three details: the exact measurement, the units and the reason the scan was performed. Keep those details beside the number as you read. The reference material below explains how published comparisons work; it cannot decide whether your individual result needs treatment.
If your report uses a different scanner, region or reference population, ask the clinic which comparison applies. Avoid substituting a convenient online table just because the units look similar. Discuss bone density or visceral fat findings with your GP.
Read the measurement
Body fat percentage describes fat mass as a proportion of the mass being measured. Start with the scanner, region and denominator before comparing the number with a reference table.
Body fat percentage references
The source uses a reversed fitness-style ranking: 90th means the lower end of the distribution, 10th the higher end. These labels do not measure fitness or health.
| Age | n | Mean ± SD | 90th | 80th | 70th | 60th | 50th | 40th | 30th | 20th | 10th |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 20-29 | 562 | 31.4± 8.5 | 22.1 | 24.5 | 26.4 | 28.1 | 29.9 | 32.1 | 35.4 | 38.3 | 43.2 |
| 30-39 | 196 | 36.6± 11.0 | 21.4 | 26.8 | 29.3 | 33.4 | 36.8 | 40.6 | 43.6 | 46.8 | 50.7 |
| 40-49 | 258 | 39.2± 9.7 | 24.5 | 31.4 | 34.3 | 37.4 | 40.0 | 42.6 | 44.5 | 48.2 | 51.0 |
| 50-59 | 437 | 41.7± 8.7 | 30.3 | 34.4 | 38.0 | 40.5 | 42.7 | 45.0 | 47.0 | 49.3 | 51.8 |
| 60-69 | 440 | 42.4± 7.7 | 32.5 | 35.5 | 38.6 | 40.8 | 42.4 | 44.9 | 47.0 | 49.1 | 52.2 |
| 70-79 | 183 | 40.4± 7.9 | 30.5 | 35.5 | 37.9 | 39.6 | 41.2 | 43.5 | 45.8 | 48.2 | 50.1 |
Choose an age to highlight a row. No values are sent to the server.
Population reference, not a target. 3,327 US adults, 95% Caucasian; GE Lunar Prodigy or iDXA. These are not Australian norms or athlete targets. Source and table ↗ · Checked 23 September 2026.
Read the percentage alongside kilograms
A percentage and a mass answer different questions. Fat mass tells you the estimated amount of fat in the scanned region. The percentage tells you how large that amount is relative to another quantity. A change in lean tissue can move the percentage even when fat mass stays the same. That is why comparing only the headline percentage can give an incomplete account of two scans.
In our invented GE example, 24.5 kg of fat divided by 68.0 kg total scanned mass is 36.0% after rounding. The same report also contains 41.0 kg lean tissue and 2.5 kg bone mineral content. Those three masses add to 68.0 kg. They are educational values, not suggested targets.
Where the comparison comes from
The GE table comes from Imboden and colleagues, who studied 3,327 US adults aged 20 to 79. Ninety-five per cent of participants were Caucasian. The measurements came from GE Lunar Prodigy and iDXA scanners. The sample was not a representative survey of Australian adults, and its percentiles do not describe an ideal athletic population.
The Hologic table is calculated from Kelly and colleagues’ NHANES reference curves. We show the White adult reference set and identify the exact age used for each displayed decade. The published supplement gives M, standard deviation and L. Standard deviation is divided by M before using the LMS formula. This distinction matters: putting the unconverted standard deviation into the formula gives incorrect values.
The two tables also use different percentile directions. The GE source ranks lower fat values towards the 90th percentile. The Hologic table uses conventional percentiles, where higher values are towards the 95th. Neither direction turns a population comparison into a health score.
What matters when the number changes
Check the fat mass, lean tissue, total scanned mass and preparation notes together. A repeat scan is most useful when it answers a question you and your practitioner agreed on before testing. Ask whether the difference is larger than the clinic’s least significant change and whether any change in scanner or software affects the comparison.
There is no single rescan interval or rate of change that follows from a percentage. Training, nutrition, illness and changes in fluid or glycogen can affect the report in different ways. Your practitioner can help choose an interval long enough to answer the question without encouraging frequent testing of ordinary variation.
Why another device gives another answer
A bathroom scale using bioimpedance and a DEXA scanner do not measure body composition in the same way. Each estimates compartments from a different physical signal and model. A difference between them does not mean your body changed between stepping off the scale and lying on the scan bed. Avoid combining readings from different methods into one trend.
If the report lists both tissue % fat and region % fat, ask which denominator is being used. In the format discussed in the original STRIVE booklet, tissue percentage excludes bone mineral from the denominator. Region percentage includes it. Comparing those columns as if they were identical can create an apparent discrepancy within a single report.
Questions for your practitioner
- Which scanner, software and reference population were used?
- Is this a total-mass or soft-tissue percentage?
- Do the kilogram changes support the same interpretation as the percentage?
Sources checked 23 September 2026: Source 1 · Source 2. New reference material prepared by DEXA Scans Australia; not included in Kristof’s earlier review.
Is the change larger than measurement variation?
Use the same measure, units, scanner and comparable preparation. The 2% starting value is an educational lean-mass example, not your clinic’s measured precision. For fat mass, the ISCD minimum acceptable precision example is 3%. Replace this with the clinic’s own precision or ask for its LSC directly.
Enter positive values to calculate an illustrative threshold.
This approximation converts relative precision using the first value. An exceeded threshold is not proof of muscle gain, fat loss or a clinically important change. Hydration and protocol differences still matter. Values stay in your browser.
Source: ISCD precision assessmentCommon questions about results
What is a good body fat percentage on a DEXA scan?
There is no single percentage that suits everyone. Published tables describe a reference population, not a target. Check the scanner, age group and sex group, then discuss the result alongside your health, strength, nutrition and reason for testing.
Why is my DEXA percentage different from my smart scale?
DEXA and bioimpedance scales estimate body compartments using different measurements and assumptions. Hydration and preparation can also affect comparisons. Neither an automatic correction factor nor combining both methods into one trend is reliable.
What does ALMI mean?
Appendicular lean mass index is arm and leg lean tissue divided by height in metres squared. It is one measure of muscle quantity. It does not measure strength and cannot diagnose sarcopenia by itself.
Is a Z-score of -1 bad?
ISCD describes adult Z-scores above -2.0 as within the expected range for age. That wording is a reference comparison, not a complete assessment of bone health. Ask your GP about the scan site, report conclusion and your medical history.
How often should I have another scan?
Agree on an interval that answers a useful clinical or training question. The reason for testing, expected change, scanner precision and whether the scan is for bone density or body composition all matter. There is no universal schedule for everyone.
Does lean mass mean muscle mass?
No. Lean soft tissue includes water and organs as well as muscle. Bone mineral content is reported separately. A change in lean tissue can reflect more than a change in muscle.
Can I compare results from GE and Hologic?
Do not treat values from different scanner families as interchangeable. Software, calibration, region definitions and reference databases differ. Ask the clinic whether a meaningful comparison is possible before interpreting a change.
Does a whole-body scan diagnose osteoporosis?
A body composition scan is not a substitute for a diagnostic bone density assessment at appropriate sites. Your GP or specialist interprets bone health findings alongside age, menopause status, fracture history and other relevant information.
How do I know if a change is larger than measurement variation?
Ask the clinic for its least significant change for the measurement. At 95% confidence, the usual calculation is 2.77 times measured precision error. Our calculator is an illustration and cannot replace the clinic’s precision assessment or confirm why a number changed.
Keep the result useful
Save the original report, including its scanner details and reference notes. At a later appointment, bring the earlier copy rather than relying on a rounded value entered in an app. Ask whether preparation, positioning and software were comparable, and whether the change is large enough to influence the decision you are making.
Return to all report measurements ↗ · Plan your next conversation ↗