InBody is a body composition analyser used in clinics, gyms and hospitals. It estimates how much of your body is muscle, fat and water rather than giving a single weight figure. The BWA 2.0 is the clinical-grade model, distinct from the simpler machines found in most gyms.
The question worth asking before you rely on the numbers: how accurate is it, and what should you actually do with the results?
How InBody works
InBody uses bioelectrical impedance analysis. A small, imperceptible electrical current passes through the body. Different tissues conduct it differently. Muscle holds a lot of water and conducts well; fat holds little and resists. The device measures that resistance and estimates composition from it.
Two design features distinguish clinical InBody devices from a bathroom smart scale.
Segmental measurement. A smart scale sends current up one leg and back down the other, measuring your lower body and estimating the rest. InBody measures each limb and the trunk separately through hand and foot contacts, which is why it can report imbalances between left and right.
Multiple frequencies. Different frequencies penetrate cell membranes differently, allowing intracellular and extracellular water to be distinguished. This is what makes body water analysis possible, and it is the main capability the BWA model adds.
How accurate is it, honestly?
The realistic answer: very good for tracking change, less reliable as an absolute figure.
Bioelectrical impedance produces an estimate derived from an equation, not a direct measurement. Compared against DEXA, generally treated as the reference standard, BIA readings can differ by a few percentage points of body fat in either direction, and the discrepancy tends to be larger at the extremes of body composition.
That sounds like a serious limitation, and for a one-off measurement it is. But it matters much less than people assume, for one reason.
The error is broadly consistent. If the device reads two percent low for you, it will read roughly two percent low next month too. So the difference between two measurements remains meaningful even when the absolute number is slightly off. That is what most people actually need: reliable direction of travel.
Why hydration is the biggest variable
Since the method depends on how water conducts electricity, anything affecting body water affects the result.
Being dehydrated typically makes body fat read higher than it is. Being over-hydrated does the reverse. Eating shortly before, exercising shortly before, drinking alcohol the night before, and the menstrual cycle all shift readings.
This is not a flaw so much as a condition of use. For repeatable results:
- Same time of day, ideally morning
- Fasted, or consistently timed after eating
- Before exercise, not after
- Normally hydrated, neither dehydrated nor having just drunk a large volume
- After using the bathroom
- Same point in the menstrual cycle where applicable
- No alcohol the previous day
- Bare feet, and remove heavy jewellery
Consistency of conditions matters more than which device you use. That is the single most useful principle in body composition tracking.
What the numbers actually mean
Skeletal muscle mass
Often the most useful figure. If you are training, this is what should be rising. Muscle gain is slow, so expect small changes over months rather than weeks.
Body fat percentage
The headline number, and the one most prone to over-interpretation. Reference ranges are population averages, not personal targets.
Visceral fat
Fat around the organs, which carries different health implications from subcutaneous fat. Clinically among the more meaningful outputs.
Segmental analysis
Genuinely useful and frequently overlooked. Notable differences between limbs can reflect training habits, an old injury, or compensation patterns worth discussing.
Phase angle
A raw measurement rather than an estimate, sometimes used as an indicator of cellular health and nutritional status. Because it comes directly from the impedance measurement rather than an equation, it avoids some of the estimation error.
Body water balance
The ratio of extracellular to total body water. Shifts can reflect fluid retention or inflammation, which is the main reason the BWA model exists.
InBody compared with other methods
DEXA is more accurate and also measures bone density, but involves a small radiation dose, costs more, and is impractical for frequent tracking.
3D body scanning such as STYKU measures shape rather than composition. It captures circumferences and visible change consistently, which is often what people actually care about, but composition figures derived from surface shape are inferred rather than measured.
Skinfold callipers are cheap and reasonably consistent in skilled hands, but highly dependent on the operator and limited to subcutaneous fat at sampled sites.
Smart scales use the same underlying principle but with fewer contact points and simpler equations. Readings will not match a clinical device, and the two should not be compared.
Combining methods works well. InBody for composition, 3D scanning for shape. They answer different questions.
How often should you measure?
Every four to twelve weeks suits most goals. Meaningful composition change takes time, and weekly measurement mostly captures noise rather than progress.
The exception is a structured programme with close supervision, where more frequent measurement may be appropriate.
Interpreting results sensibly
Track trends, not single points. One measurement is a snapshot with error attached.
Expect non-linear change. Plateaus are normal and not a sign of failure.
Watch muscle and fat separately. The most common useful finding is that weight has barely moved while fat has fallen and muscle risen. A scale would have shown you nothing at all.
Do not chase a number. Reference ranges are population statistics. Fixating on a specific figure is rarely useful and occasionally harmful.
A note on healthy use
Frequent measurement suits some people and not others. If tracking numbers tends to make you anxious, or drives restriction, less frequent measurement is the better choice, and there is no obligation to measure at all. Strength, energy, sleep and how clothes fit are all legitimate measures of progress.
If your relationship with food or your body feels difficult, that is worth raising with your GP, and body composition scanning may not be the right tool at the moment.
Who should not use InBody
Bioelectrical impedance passes a small current through the body and is generally not recommended if you have a pacemaker or other implanted electronic device. Tell the clinic beforehand.
It is also generally avoided in pregnancy, as the estimating equations are not validated for it.
Frequently asked questions
Is InBody more accurate than a smart scale?
Yes, meaningfully. Segmental measurement and multiple frequencies give considerably more information and better reliability than a two-contact scale.
Why do my gym and clinic readings differ?
Different models, electrode placement and estimating equations. Readings do not transfer between devices. Pick one and stay with it.
Does the test hurt?
No. The current is imperceptible. You stand holding handles for around a minute.
How long does it take?
The scan itself takes about a minute. Allow longer for the consultation that makes the results useful.
Can it detect health problems?
It is not a diagnostic test. Some outputs, such as visceral fat and body water balance, carry health relevance worth discussing with a clinician, but it does not diagnose anything.
What should I wear?
Light clothing, bare feet. Remove heavy jewellery. Keep it consistent between measurements.
Body composition analysis in Chiswick
We use InBody BWA 2.0 alongside STYKU 3D body scanning at Omnia Lifestyle, 8-9 Bedford Corner, The Avenue, Chiswick, London W4 1LZ, a short walk from Turnham Green station. Limited parking is available on request when booking.
Every scan includes a consultation, because the numbers are only useful once someone explains what they mean, what they do not mean, and how often it is genuinely worth measuring.
Learn more about InBody BWA and STYKU, compare the different scanning methods, or book an assessment.
This article is general information, not medical advice. Body composition measurements are estimates and should be interpreted alongside your health history.
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