How to read your DEXA results.

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.

Calculate it from the report

Take the total fat mass, not total body weight. Convert height to metres, multiply that height by itself, then divide fat mass by the result. For the invented example, 24.5 ÷ (1.68 × 1.68) gives approximately 8.68 kg/m². Dividing 68 kg body weight by height squared would calculate BMI instead.

Height errors matter because the denominator is squared. If you cannot find height on the report, ask the clinic which value it entered. A report without FMI can still contain enough information to calculate it, provided the fat mass covers the whole body rather than just the trunk or a limb.

Read the classification in context

Kelly and colleagues proposed FMI categories by matching their prevalence to established BMI categories at age 25 in the US reference population. The category names in the table are the authors’ terminology. They are not a personal diagnosis, a treatment plan or an Australian screening recommendation.

FMI separates fat mass from lean tissue in its numerator, unlike BMI. That makes it useful for describing body composition, but it does not measure where fat is stored, physical fitness, nutrition adequacy or metabolic health. Two people with the same FMI can have different reasons for testing and different needs.

The classification and a percentile table are also different tools. A category uses a specified boundary; a percentile locates a value in a selected distribution. Do not treat a shift across a rounded category boundary as proof of an important biological change.

What to compare over time

If adult height is unchanged, FMI mainly follows measured fat mass. Check that repeat scans use the same whole-body definition and comparable preparation. A change in the reported height can alter FMI without any change in fat mass. Keep the original report values so the calculation can be checked.

When looking at a GE report, the scanner-specific Imboden FMI percentiles provide a separate population comparison. The Kelly classification originated from Hologic NHANES data and should not be treated as an interchangeable manufacturer-specific diagnostic scale. Ask which interpretation your clinic uses and why.

Avoid turning a category into a goal

The purpose of the table is to explain a term you may see on a report. It cannot determine a suitable body composition for an athlete, someone recovering from illness or a person with a history of restrictive eating. A practitioner considers symptoms, training demands, medical history and the reason for testing alongside the scan.

There is no recommended timetable for moving between FMI categories. If you are changing nutrition or training, agree on what outcome matters and how it will be assessed. Energy, recovery and performance may be more useful immediate observations than a small movement in one index.

Keep the compartments separate

Total lean tissue is not the same thing as total muscle. DEXA separates estimated fat, lean soft tissue and bone mineral compartments. A result labelled lean plus BMC combines two of those compartments. Before comparing reports, check whether the bone mineral component is included in each number.

Appendicular means the arms and legs. Appendicular lean mass is the combined lean soft tissue in those regions. Research may use the term appendicular skeletal muscle mass for this DEXA-derived estimate, but the scanner does not directly isolate every muscle fibre. Region boundaries and positioning affect the analysis.

Calculate the index

ALMI divides appendicular lean mass in kilograms by height in metres squared. Our invented example uses 17.6 kg and 1.68 m: 17.6 ÷ 1.68² is about 6.24 kg/m², displayed as 6.2. This is separate from the example’s total lean tissue value of 41.0 kg.

If your report uses a different abbreviation, check the definition. Some indices divide by BMI rather than height squared. Values using different denominators cannot be read against the same cut-point. Keep the original units and formula in your tracking notes.

What the research cut-points mean

EWGSOP2 is a European consensus on sarcopenia, primarily concerned with older people. Its approach puts low strength at the centre of assessment; low muscle quantity or quality helps confirm the condition, and physical performance informs severity. A scan number alone does not complete that assessment.

The table below shows the consensus cut-points. They are not athlete reference ranges and were not designed to classify a healthy young adult’s training progress. A 25-year-old with an ALMI of 7.5 is not “nearly sarcopenic” on the basis of that value. Equally, a value above a listed boundary does not prove that strength or function is normal.

What changes lean tissue readings

Fluid balance and stored carbohydrate can influence measured lean tissue. Food, drink, exercise and recent illness can make repeat conditions less comparable. This is why a short-term increase should not automatically be described as kilograms of new muscle.

For training follow-up, record preparation and ask for the clinic’s precision assessment. At an illustrative 2% precision on 50 kg lean tissue, the 95% least significant change calculation is 2.77 kg. That is not a universal scanner limit. Use the clinic’s own measured LSC when available.

Discuss the scan alongside strength, recovery, daily function and the training programme. Nutrition and resistance exercise are topics a practitioner may discuss, but the report alone cannot prescribe protein intake, loading or a rescan date. Choose a repeat test only when the result is likely to influence a decision.

Read the label before the colour

Visceral fat is fat inside the abdominal cavity. It is different from all abdominal fat and from the android region used in body composition analysis. A report can contain both an android measurement and a VAT estimate without those labels referring to the same compartment.

GE CoreScan reports can give VAT mass and volume. Hologic software can report VAT area and mass. Software version and analysed region matter as well as the manufacturer name. Do not transfer a number from one unit to a threshold in another unit.

What a population median tells you

The GE table summarises medians reported in a US iDXA cohort of 649 adults. A median is the middle of the reference distribution, not a recommended upper limit. The broad 25 to 49 age group also contains people at many different stages of life.

Our invented example has VAT of 0.62 kg and 655 cm³. Those are slightly above the reported female median of 0.55 kg and approximately 579 cm³ for ages 25 to 49 in that cohort. That observation does not label the example healthy or unhealthy, and it cannot determine a treatment need.

A report’s coloured categories may come from a manufacturer-specific interpretation system. We have not independently verified the requested Hologic manual thresholds for the exact software version, so they are not reproduced here as advice. Ask your clinic for its current manual and reference.

Accuracy is not interchangeability

Validation research compares DEXA estimates with another imaging method such as CT. Agreement at a group level does not mean every individual estimate is exact, or that two manufacturers’ values can be swapped. Later cross-system research specifically examines these differences.

When tracking, use the same scanner and analysis protocol where possible. Ask whether a software change or region adjustment affects comparability. Keep the complete report rather than recording only a colour label or one rounded number.

What to do with a concerning result

Discuss your visceral fat result with your GP. The useful question is how it fits your history and other relevant findings, not simply whether it is above a cohort median. Your GP may consider measurements and tests beyond the scan. The DEXA report is one piece of that conversation.

A dietitian or other treating practitioner can help translate agreed goals into practical steps. A generic target number or guaranteed timeline would miss differences in health, medication, training and circumstances. If repeating the test, agree what decision the new result would inform and ask about VAT-specific repeatability.

Do not calculate a personal risk percentage from the table. The table describes the published population; it does not measure your chance of a future event. A change smaller than the clinic’s reliable measurement threshold may also be difficult to distinguish from ordinary variation.

Android and gynoid are regions

Android refers to an abdominal region; gynoid refers to a region around the hips and upper thighs. The software draws these regions using its analysis rules. An android result is not a direct synonym for visceral fat, because abdominal tissue includes other compartments.

An android-to-gynoid ratio may compare regional fat percentages. Read the report definition before calculating it yourself. Dividing android fat kilograms by gynoid fat kilograms is a different operation if the report expects a ratio of percentages.

Use the matching reference table

Imboden and colleagues published GE-specific percentiles for android/gynoid and trunk/limb ratios. Their sample was predominantly Caucasian US adults scanned on Lunar Prodigy or iDXA. The tables do not establish a universal ratio that everyone should aim below.

The study’s reversed ranking puts lower values towards the higher numbered percentiles. This presentation describes the distribution in that source. It does not turn a regional ratio into a fitness grade, nor does a low ratio necessarily mean that all relevant health measures are favourable.

Trunk/limb and trunk/leg ratios are not interchangeable. A denominator containing all limbs includes the arms as well as the legs. The name, units and formula should be recorded along with the value. The exact region definitions are part of the measurement.

A small asymmetry is not an injury diagnosis

Left and right regions let a practitioner compare corresponding limbs. Compare the same compartment on both sides: left arm lean tissue with right arm lean tissue, for example. Comparing fat on one side with lean tissue on the other creates a meaningless difference.

Our example shows a 0.3 kg lean difference. We do not call this “normal” or “under typical asymmetry”, because a universal threshold is not established by the cited tables. Positioning, analysis boundaries, limb size and the reason for the test all affect what a difference means.

What matters at a repeat appointment

Ask whether the regions were reviewed and drawn consistently. A small change in a boundary can shift tissue from one region into another without changing whole-body composition. This can make a regional result look different while the total remains similar.

If the question concerns injury or function, a clinician also needs symptoms, examination and relevant history. DEXA alone cannot identify why a side differs or prescribe a rehabilitation programme. A repeated asymmetry can be worth discussing without being treated as proof of a problem.

Keep regional comparisons within the same scanner system and protocol when possible. There is no general number of weeks after which a ratio should improve. Agree on the question and the likely size of a useful change before booking another scan.

BMC and BMD answer different questions

Bone mineral content is a measured mineral mass, usually reported in grams. Bone mineral density from DXA is mineral mass relative to projected bone area, usually g/cm². Neither number is the weight of the whole skeleton, and a larger BMC does not automatically mean stronger bones.

Whole-body body composition reports may display BMC, total-body BMD and scores. A diagnostic bone density examination uses a specific protocol and accepted sites. A total-body value should not be substituted for a hip or spine result when interpreting diagnostic thresholds.

Which adults use T-score classification?

A T-score compares BMD with a young-adult reference. ISCD applies the WHO classification in postmenopausal women and men aged 50 or older, using accepted diagnostic sites. The criteria may also be applied during the menopausal transition. That does not make age alone a reason to order a scan.

For hip T-scores, the ISCD position uses a uniform White female reference and NHANES III for femoral neck and total hip. Lumbar spine reference databases are supplied by manufacturers. These conventions explain the calculation; they do not mean the reader belongs to that reference population.

How to read the bands

The WHO Study Group report, Technical Report Series 843, describes normal bone density, low bone mass and osteoporosis categories. A T-score of -1.0 sits in the normal band; values below -1.0 but above -2.5 fall in the low bone mass band; -2.5 or lower reaches the densitometric osteoporosis threshold in the appropriate setting.

A fragility fracture and other clinical factors can change assessment and management. The traditional severe osteoporosis description combines the osteoporosis BMD threshold with fragility fracture. A website cannot establish whether an injury was a fragility fracture or whether a diagnostic criterion applies to your particular examination.

Follow the report into a GP conversation

Discuss the scan site, conclusion and reason for testing with your GP. Your practitioner considers fracture history, medicines and other risk factors as well as BMD. A category is not the whole assessment, and a report without a concerning category does not rule out all fracture risk.

Follow-up testing is chosen when it can answer a clinical question. Comparing BMD across machines requires appropriate cross-calibration, and the facility’s own least significant change matters. Do not apply the body composition lean-mass calculator to a bone density result.

Medicare eligibility and clinical interpretation are separate questions. A qualifying item has a descriptor and interval conditions; a schedule fee is not the same as the clinic’s charge. The Medicare guide explains the current published items so you can check them with the referring doctor and clinic.

A reference comparison, not a percentage

A Z-score of zero is at the reference mean. A negative number is below that mean and a positive number is above it. A Z-score of -1 does not mean that bone density is one per cent low, or that someone has lost a fixed amount of bone. The scale reflects the reference distribution.

Z-scores and percentiles both describe comparison with a reference, but they are not interchangeable labels. The relationship depends on the distribution and the method used. Copy the score exactly as reported instead of turning it into a percentage without the appropriate reference calculation.

When Z-scores are preferred

ISCD prefers Z-scores rather than T-scores in women before menopause and men younger than 50. The terminology also differs: a Z-score of -2.0 or lower is described as below the expected range for age, while a value above -2.0 is within the expected range for age.

This wording should not be replaced with T-score category names. In particular, osteoporosis cannot be diagnosed in men under 50 using BMD alone. The practitioner needs the clinical setting and other findings. Children require a separate paediatric approach and are outside these adult explanations.

What does a Z-score of -1 mean?

It means the measurement is one standard deviation below the selected age-matched mean. Under the adult terminology above, that number is within the expected range for age. It does not provide an all-clear for every bone-health concern, and it does not diagnose low bone mass using the T-score bands.

If the score was unexpected, ask about the measured site, the reference database and the report’s conclusion. The clinic can check whether age and other relevant demographic inputs were entered correctly. A useful discussion starts with the whole report rather than a single signed number.

Comparisons between visits

An age-matched score can change partly because the reference comparison changes as someone gets older. Keep the absolute BMD value, scan site and scanner details as well as the score. A change in Z-score alone is not a direct measure of kilograms or percentage of bone gained.

The facility’s measurement precision and cross-calibration rules apply to follow-up bone density. Ask whether an observed BMD difference reaches the facility’s least significant change. A different scanner or database may make score comparisons misleading even when the printed numbers look similar.

Discuss bone density findings with your GP, especially when the report flags an unexpected value or you have relevant fracture or health history. The scan is a measurement used in an assessment. The appropriate next step may be clarification of the report, review of other risk factors or further clinical investigation rather than simply repeating the scan.