InBody Body Composition, Charleston SC

Reviewed by Ashley Harwyn, PA-C, ABAAHP | A4M Board Certified | Updated October 4, 2026

An InBody scan estimates body water, lean mass, and fat from one electrical reading. Here is what each number means, what moves it, and how to use it well.

An InBody scan at our Charleston and Mount Pleasant offices passes a small alternating current through your body and records how much your body resists it. From that one reading, software estimates your body water, then your lean mass and fat mass, using equations rather than a direct look inside.[1][2] So the scan is good at showing change over time, and less trustworthy as a single exact number.

You stand barefoot on the foot electrodes and hold the hand electrodes, because bare skin has to touch them for the current to pass.[6] The catch is that body water shifts with what you ate, drank, and did that day, and the printout shifts with it.[1][5] That is why we read it next to your lab work, never alone.

Key takeaways

The device measures one thing directly, your body's resistance to a small current, and estimates body water, lean mass, and fat mass from it with equations.[1][2]
In a large clinical study, the authors judged BIA and DEXA interchangeable for describing groups but not individuals, and BIA often read lean mass high and fat mass low.[3]
Basal metabolic rate and the visceral fat level are calculated, not seen. A CT comparison found limited accuracy for visceral fat by BIA.[4][6]
Food, drink, recent exercise, skin temperature, and body position all change the reading, so conditions need to match from scan to scan.[1][5]
The maker warns people with pacemakers not to take the test and urges extra caution early in pregnancy.[6]
The trend across several scans matters more than one printout, and it means most next to your waist size and labs.

Section 01 / Under the hood

What the scan records, and what it works out from that

Bioelectrical impedance analysis, or BIA, rests on a simple chain of assumptions. The more easily the current flows, the more body water the device assumes you carry, and the more body water, the more lean tissue it assumes you have.[1][3] The only thing the machine actually records is impedance, which is the body's opposition to that current, along with your weight on the scale.

Everything after that is math. Software turns impedance into total body water, then estimates fat-free mass from body water.[3] Fat mass is simply what is left of your weight once fat-free mass is counted. An expert panel convened by the National Institutes of Health concluded that BIA gives a reliable estimate of total body water under most conditions.[1] The European Society for Clinical Nutrition and Metabolism (ESPEN) found that it works well in healthy people with stable fluid balance, when the equation suits the person's age, sex, and race.[2]

One clinical study using one analyzer. Your own device and body will differ, which is why matched repeat scans matter.

Number on the report	How it is produced	How much weight to give it
Total body water	Estimated from impedance	The most dependable output under most conditions[1]
Fat-free (lean) mass	Calculated from body water with an equation	Good for trends; read 3 to 8 kg above DEXA in many BMI ranges[3]
Fat mass and body fat percent	Weight minus fat-free mass	Read 2.5 to 5.7 kg below DEXA in many BMI ranges, with poor agreement for one person[3]
Basal metabolic rate	A formula applied to fat-free mass[6]	An estimate built on an estimate, not a measured calorie burn
Visceral fat level	Estimated from impedance, shown on a 1 to 20 scale[6]	Limited accuracy against CT in a study of 414 adults[4]

Before you step on

What to mention before your scan

Choose any line that fits you. None of these is a diagnosis. They are points to raise with Ashley so the scan is safe and the numbers are readable.

The pattern is plain: the further a number sits from the raw reading, the more assumptions it carries. Basal metabolic rate and visceral fat sit at the end of a chain of calculations. That makes them rough guides, most meaningful against your own earlier scans taken the same way.

What the scan is good for

A quick estimate of body water, plus lean and fat mass worked out from it, that becomes genuinely useful when the same device is used under the same conditions and you follow the direction across several scans.

Where it gets oversold

Treating one printout as an exact body fat figure, reading the visceral fat level or metabolic rate as if they were measured directly, or comparing a scan taken after a workout and a big drink with one taken fasting.

Section 02 / Against the reference

How close does it come to a DEXA scan?

DEXA, short for dual-energy X-ray absorptiometry, sends two X-ray beams of different energy through the body to separate fat, lean tissue, and bone. Researchers treat it as the reference method for body composition.[3] It needs radiology equipment and costs more, which is why quick impedance scans are so common.

One large study compared the two methods across 3,655 measurements in adults followed at a hospital nutrition unit in France for malnutrition, obesity, or eating disorders.[3] For people with a BMI from 18.5 to under 40, BIA put fat-free mass 3.38 to 8.28 kg higher than DEXA, and fat mass 2.51 to 5.67 kg lower.[3] The authors judged the methods interchangeable for describing a group, but found agreement for an individual lacking at every BMI.[3] That study used a different analyzer, so the exact gap will vary, but the lesson holds: one reading is not a precise answer for one person.

ESPEN adds two limits. It does not recommend BIA for routine assessment at the extremes of BMI or when hydration is abnormal. And while it supports following people over time in a BMI range of 16 to 34, it says those results must be read with caution.[2]

The visceral fat number deserves its own warning. A study of 414 adults aged 40 to 82 in China compared a single-frequency BIA device with CT scans and found poor agreement.[4] Used as a yes-or-no screen, it correctly flagged visceral obesity in 65% of the women and 76% of the men who had it on CT, and correctly cleared 69% and 70% of those who did not.[4] Other analyzers may do better or worse, but no impedance scan looks at the fat around your organs directly.

Basal metabolic rate is not measured either. The manufacturer states it uses the Cunningham formula, 370 plus 21.6 times fat-free mass.[6] That means the calorie figure can only be as good as the lean mass estimate under it. If lean mass reads high, so does the metabolic rate.

Section 03 / Moving targets

Why the numbers move from one day to the next

The NIH panel listed the things that change a BIA reading: body position, hydration, food and drink, air and skin temperature, recent physical activity, and even the surface you are measured on. Its conclusion was that reliable results require these to be standardized and controlled.[1]

Drinks matter more than most people expect. In a study of 95 healthy young adults, drinking 600 mL of a sports-style carbohydrate and electrolyte drink raised body weight and the visceral fat estimate within 30 minutes, and both were still higher 90 minutes later.[5] The authors advise no fluids for at least 90 minutes before a scan.[5] Their organ fat did not change in 90 minutes. Their water did.

Exercise and heat matter too. The manufacturer explains that a workout raises blood flow and skin temperature, which lowers impedance, so it advises testing before exercise. It also advises skipping a shower or bath right before the scan, testing on an empty stomach, and using the bathroom first.[6]

The menstrual cycle plays a part as well. The maker notes that body water tends to build during the luteal phase, which can raise lean mass and lower body fat percent on the report. The size of the effect differs from person to person, and the maker suggests avoiding scans in the luteal and menstrual phases.[6] If you have periods, compare scans taken at the same point in your cycle.

Meals, drinks, and activity stack up as the day goes on, so booking repeat scans at the same hour is the simplest way to keep those factors steady.[1]

Want numbers you can actually compare? Call 843-981-0870 to book a scan. We set it up the same way every visit and read it alongside your labs and waist measurement, never on its own.

Section 04 / Safety first

Who should not have the scan

If you have a pacemaker, a defibrillator, or any other implanted electronic device, tell us before anything else, and we will not scan you. The manufacturer tells people with pacemakers not to take the test as a precaution, while noting a report of supervised testing in patients with pacemakers.[6] We follow the maker's warning. Implants that are not electronic, such as a cardiac stent or other metal implant, are a different matter: the maker says they do not pose a safety problem.[6]

Pregnancy calls for a pause. The maker says its device meets the international safety standard for medical electrical equipment and has been used in pregnancy research. It still advises extra caution early in pregnancy and leaves the final decision to the mother.[6] A body fat estimate is not what guides care during pregnancy, so we would rather wait until after delivery.

A scan is also hard to read at a very low or very high BMI, or when fluid balance is off, such as with swelling or dehydration.[2] If that applies to you, we will say so and lean on other measures.

Section 05 / Using it well

Making the scan worth your time

A single InBody printout is a snapshot of your body water that morning. A series of printouts taken the same way can show a real direction. To get there:

Use the same device, at the same time of day, every time.
Skip exercise, a shower, a meal, and large drinks beforehand, and use the bathroom first.[5][6]
Step on barefoot with clean, dry skin on the electrodes.[6]
If you have periods, aim for the same phase of your cycle.[6]
Judge the direction over several scans rather than reacting to one.

Pair the scan with a tape measure. The National Heart, Lung, and Blood Institute notes that carrying most of your fat around the waist rather than the hips raises the risk of heart disease and type 2 diabetes. Risk climbs with a waist over 35 inches for women or over 40 inches for men, measured just above the hipbones after you breathe out.[7] Blood pressure and labs fill in the rest.

At Solcara Health, Ashley Harwyn, PA-C reviews each scan alongside your history, labs, and goals. She is board certified in anti-aging and functional medicine and holds ABAAHP certification. You can be scanned at our office at 496 Bramson Ct in Mount Pleasant or at The Longevity Club, 163 Rutledge Ave in downtown Charleston. If you are losing weight on a medical weight loss plan, matched repeat scans can help show whether the change is coming mostly from fat or from lean tissue.

Medical Weight Loss

Where repeat scans can help show what kind of weight is coming off. Read Medical Weight Loss.

Annual Full Panel Labs

The blood work that gives any scan its context. Read Annual Full Panel Labs.

Nutritional Therapy

For turning a trend into practical changes in how you eat. Read Nutritional Therapy.

Cardiac Health

If your waist size or visceral fat estimate raises heart-risk questions. Read Cardiac Health.

If you are starting a weight loss medication

Read what GLP-1 weight loss costs in Charleston.

Ask Ashley

Ashley Harwyn, PA-C PA-C, ABAAHP · Founder, Solcara Health Online

Tap a question to ask

How does an InBody scan work? You stand barefoot on the foot electrodes and hold the hand electrodes while a small alternating current passes through your body. The device records how much your body resists it. Software then uses that resistance, your weight, and equations to estimate body water, lean mass, and fat mass.

What do the numbers on the report actually tell me? Total body water is the most dependable output. Lean mass and body fat percent are calculated from it and are best used to track your own trend. Basal metabolic rate comes from a formula based on estimated lean mass, not a measured calorie burn. The visceral fat level is an estimate, and a study comparing BIA with CT found limited accuracy.

Is it as accurate as a DEXA scan? No. In a large study of adults at a hospital nutrition unit, the authors judged BIA and DEXA interchangeable for describing groups, but not individuals, and BIA often read lean mass several kilograms higher and fat mass several kilograms lower than DEXA. A single result is an approximation. Repeat scans under matched conditions are better at showing your direction.

How often should I repeat the scan? No guideline sets a fixed schedule. Because hydration, meals, and exercise shift the numbers from day to day, frequent scans mostly capture water changes. Scans spaced several weeks apart, taken at the same time of day with the same preparation, are more likely to reflect real change.

Can I have a scan if I have a pacemaker or I am pregnant? If you have a pacemaker, a defibrillator, or another implanted electronic device, we will not scan you, because the manufacturer warns people with pacemakers not to take the test. Non-electronic implants such as stents are a different case. During pregnancy, the manufacturer advises extra caution, especially early on, and a body fat estimate does not guide pregnancy care, so we would rather wait until after delivery.

How should I prepare? Come at the same time of day as your last scan. Skip exercise, a shower or bath, a meal, and large drinks beforehand, since a sizable drink can raise the visceral fat estimate for at least 90 minutes. Use the bathroom first. If you have periods, book at the same point in your cycle as last time.

A scan read in context, not in isolation

Book an evaluation at The Longevity Club, 163 Rutledge Avenue downtown, or our Mount Pleasant office.

BOOK A CONSULTATION →

Or call 843-981-0870

About the author

Ashley Harwyn, PA-C, founder of Solcara Health in Charleston, South Carolina.

Ashley Harwyn, PA-C, ABAAHP

Founder, Solcara Health · Diplomate, American Board of Anti-Aging Health Practitioners (ABAAHP)

Ashley has practiced medicine for more than fifteen years. Her path into it began at home, with a family member born with a congenital heart defect and a childhood spent watching how much the quality of a clinician's attention could change the shape of a life. She has since practiced across a range of settings, including medical mission work in Uganda, before founding Solcara to build the kind of practice she kept wishing existed, one that treats patients as whole people and tells them the truth about what the evidence does and does not support.

Full bio →

Medical Disclaimer: This page is for educational and informational purposes only and does not constitute medical advice, and reading it does not create a patient-provider relationship. It describes general medical information and categories of care, not a recommendation that any individual start, stop, or change any test, treatment, or medication. Any diagnosis or treatment decision requires evaluation by a qualified, licensed clinician who knows your personal and family history. Consult a qualified healthcare provider before making medical decisions. Information reflects sources available as of October 4, 2026.

Ashley Harwyn, PA-C, ABAAHP, is a Diplomate of the American Board of Anti-Aging Health Practitioners (ABAAHP) through A4M and the founder of Solcara Health. Solcara serves South Carolina from Downtown Charleston (163 Rutledge Ave, Ste 202, The Longevity Club) and Mt. Pleasant (496 Bramson Ct, Ste 120).

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