Biohacking Kompakt

Treatment & Procedure

DEXA scan (body composition and bone density)

Biohacking

A DEXA scan, technically DXA for dual-energy X-ray absorptiometry, passes X-rays at two energy levels through the body and in this way separates bone, fat and fat-free tissue. In medicine it has been the standard measurement of bone density for decades. In the longevity and fitness scene it has become a body scan: body fat, the fat around the abdominal organs and the muscle mass of the arms and legs, in a few minutes and at a very low dose. The appeal is understandable, because scales and BMI cannot see what the weight consists of. For bone density the measurement is excellently supported; for the other values it measures precisely, but predicts less than is often promised.

In short

Bone density from a DEXA scan reliably predicts fractures: per standard deviation of lower density, fracture risk rises 1.5-fold, and at the hip 2.6-fold for hip fractures. Screening programmes with bone density measurement reduced hip fractures by 20 percent in three randomized trials with 42,009 participants. The radiation dose of a whole-body scan is 1 to 10 microsieverts. For body fat, visceral fat and muscle mass the measurement is highly repeatable, but its added value is open: visceral fat no longer independently predicted cardiovascular events after adjustment for BMI and waist circumference, and DXA lean mass was not consistently associated with falls, fractures or mortality in eight cohorts, whereas grip strength and gait speed were. Bone density is covered by statutory health insurance when there is a concrete reason for treatment; the German Commission on Radiological Protection has assessed a lifestyle measurement without a medical reason as not permissible.

What it is and how it measures

X-rays are attenuated to different degrees by bone, fat and fat-free tissue, and differently depending on their energy. Measuring at two energy levels makes it possible to calculate the proportions for each pixel. This produces two kinds of result: bone density at the lumbar spine and hip, expressed as a T-score compared with young adults, and, with a whole-body scan, body composition with fat mass, fat-free mass and bone mineral, broken down by trunk, arms and legs.

Newer analysis software also estimates visceral fat, that is the fat between the abdominal organs, in a section of the abdomen. For muscle mass, the fat-free mass of the arms and legs is added up and divided by height squared, the so-called ALMI. The European sarcopenia working group EWGSOP2 uses this value to confirm sarcopenia, with cut-offs of 7.0 kg/m² in men and 5.5 kg/m² in women. “Fat-free” means everything that is neither fat nor bone, so besides muscle it also includes water, organs and connective tissue.

Why people want this is obvious: anyone losing weight, for example with semaglutide, wants to know whether fat or muscle is disappearing. Anyone doing strength training wants to see progress that the scales do not show. And anyone thinking about longevity knows the message that muscle works like an organ and that belly fat has to be judged differently from hip fat. Other measurements from longevity diagnostics can be found under whole-body MRI and heart rate variability.

What is well supported

Bone density is one of the best-supported measurements in preventive medicine. It predicts fractures, its predictive power is of the same order as blood pressure for stroke, and screening programmes with bone density measurement have prevented hip fractures in randomized trials. The 2023 DVO guideline calculates fracture risk from age, sex, the total hip T-score and clinical risk factors and uses it to determine when treatment is considered or recommended, at a 3, 5 and 10 percent risk of hip and vertebral fractures over three years.

It is also well supported that DXA measures body composition with high repeatability: in healthy people, fat and fat-free mass varied by less than 1 percent between two measurements. Compared with body fat scales using bioelectrical impedance (BIA), DXA is the more accurate method, and visceral fat measured by DXA was clearly associated with later cardiovascular events in a large cohort.

What the studies show

Marshall 1996 – bone density predicts fractures

Meta-analysis of prospective cohorts from 11 study populations with about 90,000 person-years of observation and over 2,000 fractures in women. Per standard deviation of lower bone density, fracture risk rose 1.5-fold (95% CI 1.4 to 1.6). Prediction was strongest at the matching site: spine for vertebral fractures 2.3, hip for hip fractures 2.6. The authors compared the predictive power with that of blood pressure for stroke.

Merlijn 2020 – screening with bone density measurement reduces hip fractures

Meta-analysis of the three randomized trials ROSE, SCOOP and SOS with 42,009 participants from the general population. Screening for high fracture risk included at least a bone density measurement, after which people at high risk received anti-osteoporosis medication. Compared with usual care, hip fractures fell by 20 percent (HR 0.80; CI 0.71 to 0.91) and major osteoporotic fractures by 9 percent (HR 0.91). To prevent one hip fracture, 272 people had to be screened, 124 measured and 28 treated. All-cause mortality did not differ (HR 1.04).

Zhu 2025 – visceral fat and cardiovascular events

In the Australian Busselton study, 4,866 people aged 46 to 70 were measured by DXA and followed for a median of 7.9 years. Per standard deviation of additional visceral fat, the risk of cardiovascular events rose by 26 percent in men (HR 1.26) and by 30 percent in women (HR 1.30), and for coronary events by 28 and 40 percent respectively. After additional adjustment for BMI and waist circumference, the association was no longer independent. The authors leave open whether the DXA value improves risk assessment beyond simple body measurements.

Cawthon 2020 – muscle mass by DXA versus grip strength

The Sarcopenia Definitions and Outcomes Consortium analysed eight cohorts with 13,421 men and 4,828 women living at home; for mortality, follow-up averaged 8.8 years. Low grip strength predicted falls, hip fractures, mobility limitation and death, with risk ratios mostly between 1.2 and 3.0. Fat-free mass from DXA, relative to height, by contrast was not consistently associated with these events. Risk was highest in people who were both weak and slow.

Esco 2015 – body fat scales compared with DXA

45 university athletes were measured with a multi-frequency BIA and with DXA. BIA was on average 3.3 percentage points lower for body fat percentage and 2.1 kg higher for fat-free mass. The limits of agreement were ±5.6 percentage points for body fat and ±3.7 kg for fat-free mass: in an individual case the scales can therefore be clearly off, even if the group average is only slightly shifted.

Henriksen 2021 – how precise repeat measurements are

30 healthy people and 30 people with colorectal cancer were scanned twice in a row with repositioning. In the healthy participants, the measurement variation for fat, lean and total masses was between 0.40 and 0.88 percent, and for visceral fat 5.3 percent. The smallest reliably detectable change in healthy people was 484 g of fat mass, 618 g of lean mass and 81 g of visceral fat. Smaller differences between two scans cannot be distinguished from measurement noise.

What users report

No published surveys were found on people who use DXA as a longevity or fitness scan. From osteoporosis care there is an interview study with 18 patients who had had a fracture without major trauma and had been measured before: only 6 reported their result correctly. Nine interpreted “no news” as good news, six did not consider an abnormal result serious or accurate (Sale 2010). These are individual accounts, not proof of efficacy, but an indication that a measurement only has an effect once it is discussed in an understandable way.

Where the data stop

Even the well-supported bone density predicts a risk, not a fracture: according to Marshall 1996, the measurement cannot predict who will actually break a bone. Screening reduced hip fractures but did not measurably extend life. Without treatment and with a T-score above −1.0, the DVO guideline generally considers measurement intervals of more than five years sufficient.

For body composition, the decisive step is missing. No study shows that healthy people who track their body fat or muscle mass by DXA live healthier or longer. In 2015 the German Commission on Radiological Protection stated that there are no studies showing an influence on relevant endpoints in people with obesity or diabetes, and that the result does not lead to recommendations beyond those that are indicated anyway. In Busselton, visceral fat lost its independent predictive value as soon as waist circumference and BMI were known. For muscle, strength and gait speed count for more than measured mass in the large cohorts; that is why EWGSOP2 puts strength first and uses mass only for confirmation. An abnormal ALMI value in a strong person means something different from the same value in a weak person.

For follow-up measurements: changes below about half a kilogram of fat or lean mass are within measurement noise, and for visceral fat the variation of just over 5 percent is considerably larger.

Status, approval and legal

In Germany, bone density measurement by DXA is covered by statutory health insurance when concrete findings suggest targeted drug treatment, for example after a fracture typical of osteoporosis, with an already diagnosed osteoporosis or before planned high-dose cortisone therapy; this is how Techniker Krankenkasse summarises the rules of the Federal Joint Committee (G-BA). As early detection without such indications it is a self-pay service. The basic fee under the German medical fee schedule is around 30 euros, and the price range as a self-pay service was 30 to 70 euros according to the consumer advice centre (Verbraucherzentrale) in 2022. For body composition there is no insurance coverage and no reliable public price overview.

The 2023 DVO guideline recommends offering basic diagnostics with bone density measurement from age 70, from age 50 in a risk constellation judged relevant by a physician, and promptly after any fracture from age 50.

Under radiation protection law, every use of X-rays on humans requires a justifying indication: a physician with expertise in radiation protection must determine that the health benefit outweighs the radiation risk (§ 83 German Radiation Protection Act). In 2015 the German Commission on Radiological Protection assessed that DXA without a medical indication is not permissible, that body composition measurements to monitor obesity or diabetes, to prevent sarcopenia and in sports medicine are only permissible within approved studies, and that assessing athletic performance is not a medical indication. For the early detection of osteoporosis after menopause, it considered DXA not justified without additional risk factors.

Safety

The radiation dose is among the lowest in X-ray diagnostics. The German Commission on Radiological Protection gives an effective dose of 1 to 10 microsieverts for the whole-body scan, 0.2 to 15 for the lumbar spine and 1.5 to 10 for the hip; for comparison, 10 to 2,500 microsieverts for conventional X-rays and 100 to 3,000 for quantitative computed tomography. In 2015 the German Commission on Radiological Protection named a technical weight limit of 140 kg body weight.

The real risk lies in interpretation: a T-score is a comparison with young adults, not a verdict, and differences between two scans below the smallest detectable change are neither progress nor decline. Anyone who measures regularly also adds up the dose. With an abnormal bone result, the assessment of overall fracture risk belongs in the hands of a physician.

BK-Score Supported, with caveats

Human evidence7
Mechanism7
Safety data8
Hype gap5
Track record of use9

Evidence 7, because bone density is as well supported as a measurement as few values are: a meta-analysis of 11 cohorts with about 90,000 person-years shows a 1.5-fold higher fracture risk per standard deviation of lower density, and at the hip a 2.6-fold higher risk of hip fractures, and three randomized screening trials with 42,009 participants reduced hip fractures by 20 percent; for body fat, visceral fat and muscle mass, by contrast, there are only observational data and no study showing a benefit of the measurement in healthy people. Mechanism 7, because the physics of the measurement is understood and its repeatability has been measured, but the chain from the measured value to health is closed only for bone density. Safety 8, because the radiation dose is precisely quantified at 1 to 10 microsieverts for the whole-body scan and the measurement has been routine for decades; how misunderstood results play out has hardly been studied. Hype 5, because bone measurement is promoted soberly, but the longevity values promise more than they deliver: in Busselton, visceral fat no longer independently predicted cardiovascular events after adjustment for BMI and waist circumference, and DXA lean mass was not consistently associated with falls, fractures or mortality in 8 cohorts. Use 9, because bone density measurement has been guideline-based routine for decades; as a pure lifestyle measurement without a medical reason, however, the German Commission on Radiological Protection considers it not permissible. Direction mixed: positive for bone density, open for body fat, visceral fat and muscle mass as longevity markers.

The score rates the state of knowledge, not the substance. “Safety data 8” means well studied – not harmless. “Track record of use 9” means used long and widely – that is not proof of efficacy.
Subjective assessment by Biohacking Kompakt based on published scoring rules – not a scientific rating and not a medical recommendation. Rules and all ratings (German)

Frequently asked questions about DEXA scans

What does a DEXA scan measure?

A DEXA scan uses X-rays at two energy levels to measure bone density at the spine and hip and, as a whole-body scan, body composition: fat mass, fat-free mass and bone mineral, broken down by body region. Analysis software also estimates visceral fat and the muscle mass of the arms and legs.

Is a DEXA scan more accurate than a body fat scale?

Yes. In a comparison study with 45 female athletes, a multi-frequency BIA was on average 3.3 percentage points below DXA for body fat, and in individual cases off by up to 5.6 points. In healthy people, DXA measures with a variation of less than 1 percent between two scans.

How high is the radiation exposure from a DEXA scan?

Very low. The German Commission on Radiological Protection gives 1 to 10 microsieverts for the whole-body scan and 10 to 2,500 microsieverts for conventional X-rays. Nevertheless, every measurement in Germany requires a justifying indication from a physician.

Does health insurance pay for a DEXA scan?

For bone density measurement, yes, when concrete findings suggest targeted drug treatment, for example after a fracture typical of osteoporosis or with known osteoporosis. As early detection without a reason it is a self-pay service, costing 30 to 70 euros according to the consumer advice centre in 2022. Body composition is not covered by statutory health insurance.

Does the DEXA value for visceral fat say more than a tape measure?

Based on the data so far, hardly. In the Busselton study with 4,866 adults, visceral fat predicted cardiovascular events, but no longer independently after adjustment for BMI and waist circumference. Whether the DXA value improves risk assessment beyond that is open.

How meaningful is muscle mass from a DEXA scan?

Limited. In eight cohorts with more than 18,000 older people, DXA lean mass was not consistently associated with falls, fractures or mortality, whereas grip strength and gait speed were. The European definition of sarcopenia therefore puts strength first and uses mass for confirmation.

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Information only, not medical advice and not a usage or dosage recommendation. Prescription-only and unapproved substances belong in the hands of a physician. Last updated: 2026-10-15.