At just about every gym you go into these days, you’ll see a sign advertising InBody scans. Or, maybe it’s even a freebie thrown in when you buy personal training. They say it will tell you your body composition and help you reach your goals – can it?
Can a little machine with handles really tell you your body fat%, lean mass, and body composition? If you asked 10 years ago, we’d tell you not so much. However, with advancements in technology, our answer has changed. Are InBody results accurate?
What Is InBody?
InBody is a brand of advanced body composition analyzers that use something called bioelectrical impedance analysis (BIA) to measure the composition of your body.
Body fat percentage
Muscle mass
Visceral fat
Total body water (intracellular & extracellular)
Basal metabolic rate (BMR)
Segmental analysis (muscle/fat in each arm, leg, and torso)
Now, there are numerous types of BIA analyzers out there, with bathroom scales being the most common. However, while InBody uses BIA, its technology is more sophisticated.
Uses Multiple Frequencies. Normal BIA uses a single frequency to measure body composition. On the other hand, InBody sends multiple frequencies through your body and measures each body segment (arms, legs, torso) separately.
Uses Multiple Electrodes. Normal BIA generally has you either stand on a scale with electrodes or hold a pair. InBody has you stand on electrodes and hold a pair.
Uses Other Biometrics To Calculate Measurements. Normal BIA generally just uses a standard equation. InBody also adjusts for height, age, and water balance.
InBody Vs. DEXA: Is InBody Accurate?
When talking about body composition analyzers, DEXA (Dual-Energy X-ray Absorptiometry) is generally considered the gold standard. It’s medical-grade equipment that uses two low-energy X-Ray beams, which are absorbed into your body.
Fat
Muscle
Bones
If you want to know how body composition testing holds up, you compare it to DEXA, as it sets the bar.
As such, there have been several studies, and InBody has actually shown very impressive results.
Study 1. A study from 2020 tested three models: InBody230, InBody720, and InBody770. It found that InBody had a very high correlation (≥ 0.98) across several days.¹
More interesting is that the higher models provided minimal benefits when compared to their entry-level counterparts.
Study 2. In 2021, a study used InBody230 on 10-12-year-old children. It also found very good accuracy when compared to DEXA.²
Nearly perfect associations (0.97−0.99)
Excellent absolute inter-device reliability(0.04−1.9%)
Excellent relative inter-device reliability (0.98−1.00)
While small, the primary issue in readings concerns fat and muscle measurements.
Muscle mass is underestimated
Fat mass is overestimated
While there is some error with the exact fat and muscle reading, it’s small and still reliable for use.
Study 3. In 2024, the InBody770 was tested on healthy military personnel. It took tests at multiple parts of the day to test its variability and found almost perfect correlation (0.98–0.99).³
When measurements were compared to DEXA, it was also highly accurate, with an acceptable margin of error for measurements.
Body fat percentage: Slightly underestimated (- −4.0 ± 2.8%)
Fat mass: Slightly underestimated (- −2.9 ± 2.0 kg)
Lean mass: Slightly overestimating (+2.8 ± 2.1 kg)
Keep in mind that InBody has numerous models available, and not every one has been tested.
However, they all use the same technology, and as we saw with the first study, even the entry-level machine performed amazingly.
What Causes Differences In InBody Readings?
You have probably heard users speak about getting wildly different readings. There can be several reasons for this, either caused by machines or the user.
Machine-Caused Differences
Error can be caused by machines, but it usually comes down to poor maintenance or software issues.
Calibration & Maintenance. Poorly maintained or uncalibrated machines can drift over time, especially if not serviced regularly.
Electrode Wear or Damage. Dirty, corroded, or worn contact points (hand or foot electrodes) can reduce conductivity and affect results.
Firmware/Software Versions. Slight differences in how raw impedance is interpreted can exist across firmware updates or regional versions.
This can easily be mitigated by using a machine that is regularly updated and maintained.
User-Related Issues
A major cause simply comes down to the user and how they use the machine.
Hydration Status: BIA uses electrical frequencies that travel at different speeds through different tissues. Muscle holds onto water, so your hydration can affect measurement.
Dehydration = falsely low lean mass, high fat
Overhydration = falsely high lean mass, low fat
Food/Water Intake: Eating or drinking before the test can skew intra-/extracellular water readings.
Exercise Before Scan: Raises temperature and shifts water into muscles. This leads to reading high muscle and lower fat.
Bladder/Bowel Fullness: Extra fluid/mass in the torso can slightly alter readings
Menstrual Cycle (for women): Water retention during menstruation may increase total body water and affect fat/muscle estimates.
Time of Day: Morning = most consistent. Later in the day, fluctuations from meals, movement, and hydration accumulate.
How To Optimize Your InBody Results
While InBody has come a long way with technology and its accuracy, there are some things to make sure your results are as accurate as possible.
1. Do it first thing in the morning, before eating or drinking. Food, fluids, and caffeine can temporarily alter total body water and skew results.
2. Always use the bathroom beforehand. Bladder or bowel contents affect your weight and can slightly distort fat and water measurements.
3. Avoid exercise for at least 6–12 hours before. Intense training causes temporary shifts in fluid distribution (e.g., swelling in muscles), which can misrepresent lean mass or hydration.
4. Wear similar, light clothing (or none if private). Clothes add variable weight and can affect segmental analysis if they cover electrodes or contain metal.
5. For women, test during the same menstrual phase—ideally mid-cycle. Avoid scans during menstruation or PMS, when water retention can falsely elevate fat mass or ECW ratios.
6. Simulate the reading every time. Once you start, do your best to repeat your readings as closely as possible. For example, use the same machine, wear the same clothes, and go at the same time.
Final Verdict: Are InBody Scales Actually Reliable?
After reading all the research on the newer models, we were actually impressed with how accurate InBody seems to be.They have likely gotten some bad impressions due to people either assuming they’re BIA, like your normal bathroom scale, OR due to maintenance or user error. While there is some error and variability, if you use InBody as we directed above, it is a highly reliable piece of equipment to help guide you on your fitness journey.
References
McLester CN, Nickerson BS, Kliszczewicz BM, McLester JR. Reliability and Agreement of Various InBody Body Composition Analyzers as Compared to Dual-Energy X-Ray Absorptiometry in Healthy Men and Women. J Clin Densitom. 2020;23(3):443-450. doi:10.1016/j.jocd.2018.10.008 https://pubmed.ncbi.nlm.nih.gov/30472111/
Larsen MN, Krustrup P, Araújo Póvoas SC, Castagna C. Accuracy and reliability of the InBody 270 multi-frequency body composition analyser in 10-12-year-old children. PLoS One. 2021;16(3):e0247362. Published 2021 Mar 26. doi:10.1371/journal.pone.0247362 https://pubmed.ncbi.nlm.nih.gov/33770106/
Looney DP, Schafer EA, Chapman CL, et al. Reliability, biological variability, and accuracy of multi-frequency bioelectrical impedance analysis for measuring body composition components. Front Nutr. 2024;11:1491931. Published 2024 Dec 3. doi:10.3389/fnut.2024.1491931 https://pubmed.ncbi.nlm.nih.gov/39691170/
