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DEXA Scan vs InBody: Which Is More Accurate for Body Composition?

  • Mar 19
  • 3 min read

Updated: Apr 9

If you have ever stepped on an InBody machine at the gym and wondered how accurate the results really are, you are asking the right question. InBody and other bioelectrical impedance analysis (BIA) devices are convenient, but their accuracy gap compared to DEXA is significant. This matters when you are making decisions about your training, nutrition, or health.



How Each Method Works


DEXA (Dual-Energy X-ray Absorptiometry) passes two low-dose X-ray beams through your body. Because fat, muscle, and bone each absorb X-rays differently, the scanner directly measures the mass of each tissue type across every region of your body. It is a direct measurement, not an estimate.


InBody and other BIA devices send a weak electrical current through your body via hand and foot electrodes. The device measures how much the current is impeded (resistance) and uses algorithms to estimate how much of your body is water, fat, and lean tissue. The key word is "estimate." BIA does not directly measure fat or muscle. It measures electrical impedance and then calculates body composition from that.


The Accuracy Gap: What the Research Shows


DEXA is considered the clinical gold standard for body composition measurement, with an accuracy margin of approximately 1 to 2 percent for body fat percentage.


InBody devices have shown to carry a margin of error of 3 to 15 percent under real-world conditions.


In percentage terms, this difference is substantial.


If your true body fat is 25%, DEXA will likely read between 23% and 27%. An InBody might read anywhere from 20% to 30%. That is a 10-percentage-point spread. That is the difference between being classified as healthy and being classified as at-risk.


A large 2025 study of 1,000 healthy adults compared the InBody 770 against DEXA under typical (non-fasted, uncontrolled hydration) conditions. The InBody underestimated fat mass by an average of 3.7 kg in men and 1.9 kg in women, and underestimated body fat percentage by about 4.2 percentage points in men. The study also found particularly large discrepancies for visceral fat estimates.


The Hydration Problem


This is the single biggest issue with BIA accuracy. Because InBody measures electrical impedance through body water, anything that changes your hydration level changes your results:

  • Drinking 500 mL of water (roughly two cups) has been shown to shift BIA body fat estimates by 2 to 3 percent.

  • Dehydration causes BIA to overestimate body fat because less water means higher electrical resistance.

  • A recent meal, a coffee, alcohol, or exercise within a few hours of testing can all shift results meaningfully.

  • Time of day matters. Most people are more hydrated in the evening than in the morning, producing different readings on the same day.


DEXA measures tissue density directly via X-ray absorption. It is largely unaffected by hydration fluctuations, meal timing, or recent exercise. This is why DEXA is the reference standard used in research studies, including the studies that validate (or invalidate) BIA devices.


What InBody Cannot Measure


Beyond accuracy, there are measurements that DEXA provides which InBody simply cannot:


  • Bone mineral density. DEXA measures your bone density across the whole body. InBody cannot assess bone health at all. This matters for anyone concerned about osteoporosis or long-term skeletal health.


  • Accurate visceral fat. While InBody does report a visceral fat area estimate, research shows large discrepancies between InBody visceral fat readings and those measured by DEXA or CT scans. DEXA visceral fat measurements correlate strongly with CT (the true gold standard for visceral fat) at r = 0.93.


  • True regional fat distribution. DEXA provides precise android (waist) and gynoid (hip) fat measurements and the A/G ratio. This is a clinically validated marker of cardiovascular risk. BIA regional estimates are derived from impedance in each limb segment, which is less precise.


When Does InBody Make Sense?


InBody is not useless. It has legitimate applications:


  • Quick, low-cost progress checks between DEXA scans, as long as you control hydration and timing.


  • Tracking broad trends over time (months) when you cannot access DEXA regularly.


  • Gym-based screening where the goal is motivation rather than clinical precision.


But for establishing an accurate baseline, making clinical or training decisions, tracking body recomposition, measuring visceral fat, or assessing bone health, DEXA is the clear choice. The accuracy gap between the two methods is too large to ignore when the data actually matters.



At Precision Body Lab in Miranda, we use clinical-grade DEXA technology to give you body composition data you can trust. Book your scan today and see what your body is actually made of and not what an algorithm estimates.


Ready to see your own results?


Book a DEXA body composition scan at Precision Body Lab - Sydney's dedicated DEXA clinic in Miranda. Trusted by 1,000+ clients, rated 5 stars on Google.



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