Body composition, not body weight: the seca mBCA Ultra arrives at SŌMA, a first for Bali
Published by SŌMA Aesthetics and Longevity Club · Written and medically reviewed by Dr Muhammad Nadim (M.Biomed) · Updated 30 September 2026
SŌMA Aesthetics and Longevity Club is the first clinic in Bali to use mBCA Ultra. It is a high-precision, medical-grade body composition analyser of the kind used in hospital nutrition and obesity units rather than gyms, and in 24 seconds it reports what a bathroom scale cannot: how much of the body is fat and how much is muscle, where the fat sits, how body water is distributed and how healthy the cells are. The clinic uses it to run its medical weight-management programme with Wegovy and Mounjaro, to measure rather than estimate in body contouring, and as a core marker in the OPTIMIZE and FUTURE-PROOF longevity programmes. A doctor reads every scan with the patient.
Why weight was never the right number
A scale collapses everything into one figure. It cannot distinguish two kilograms of fat from two kilograms of muscle, or fat loss from a night of poor hydration. That mattered less when the tools for losing weight were slow. It matters a great deal now that GLP-1 medicines can remove 15 to 20 per cent of body weight in a little over a year, because a share of what comes off is lean tissue.
The figures are worth knowing. In the DEXA substudy of the STEP 1 trial of semaglutide 2.4 mg (140 participants), total fat mass fell by 19.3 per cent over 68 weeks, visceral fat by 27.4 per cent and lean body mass by 9.7 per cent; the ratio of lean to fat improved, but lean tissue still declined. In the SURMOUNT-1 substudy of tirzepatide (160 participants, 72 weeks), fat mass fell by 33.9 per cent and lean mass by 10.9 per cent, which means roughly a quarter of the weight lost was lean tissue. Those are averages. An individual patient may be losing far less muscle than that, or far more, and the only way to know is to measure.
That is the case for the device. Weight loss is visible on a scale. Fat loss, muscle preservation and visceral fat are visible only with a proper body composition measurement, and those three decide whether a weight-loss programme was worth doing.
What is the seca mBCA Ultra
Seca is a German medical-scales manufacturer, and the mBCA (medical Body Composition Analyzer) is its clinical BIA platform. The Ultra is the current top model: an 8-point bioelectrical impedance platform with a handrail, contactless ultrasonic height measurement and software that plots every parameter over time from the second scan onwards. The patient stands on it barefoot, holds the rails, and the report is on screen 24 seconds later.
What separates it from a body-fat scale at home or the analyser at a gym is validation. Consumer devices estimate body composition from equations tuned on whichever population the manufacturer tested. seca's algorithms were checked against reference methods in peer-reviewed studies, largely from Kiel University: fat-free mass against the four-compartment model (R² 0.98), total body water against deuterium dilution (R² 0.98), extracellular water against sodium bromide dilution (R² 0.95) and skeletal muscle mass against whole-body MRI (R² 0.97), the closest thing to counting the muscle directly. A separate study confirmed that the fat-free mass and muscle equations hold in people with a BMI of 30 or more, which is precisely the group most analysers misjudge. The reference ranges it uses come from studies of several thousand adults across ethnicities and ages, including a 2023 dataset that set normal values for visceral fat, fat mass index, skeletal muscle index and the water ratio in nearly 2,000 adults aged 18 to 97. The papers are listed at the end.
It is not a DEXA scan, and that should be said plainly. DEXA measures bone density, which BIA cannot, and DEXA remains the research standard for lean mass. What the mBCA provides is reference-validated fat, muscle and water measurements with no radiation, in under a minute, repeatable every month. For tracking a person over time, which is what a clinic needs, that is the more practical tool.
What the scan measures, and what each number means for the patient
Measurement | What it is | What it tells the patient and the doctor |
Fat mass and fat mass index | Total body fat, in kg and as an index adjusted for height | The number that should fall on a weight-loss programme; the index allows comparison with reference ranges rather than a bare percentage |
Fat-free mass | Everything that is not fat: muscle, organs, bone, water | Should hold steady or rise while fat falls; a drop is the early warning that prompts a change of plan |
Skeletal muscle mass, total and by limb | Muscle in each arm, each leg and the trunk, validated against MRI | The tissue most at risk on GLP-1 medicines, the tissue EMS body sculpting is meant to build, and the tissue that predicts independence in later life |
Visceral adipose tissue | Fat packed around the organs inside the abdomen | The fat most closely linked to insulin resistance, fatty liver and cardiovascular risk; it usually falls fastest and matters most |
Total body water, extracellular and intracellular water | How much water the body carries and where it sits | A rising extracellular share can indicate inflammation, fluid retention or muscle loss; it also shows when a change on the scale was water rather than fat |
Phase angle | A raw electrical measure of cell membrane integrity and cell mass | Falls with illness, undernutrition and ageing; rises with training and recovery; one of the few whole-body markers of cellular health measurable in a clinic |
Bioelectrical impedance vector (BIVA) and body composition chart | Hydration and cell mass plotted against a reference population | Shows at a glance whether a change is lean tissue, fat or fluid, and whether the patient is drifting towards sarcopenia or sarcopenic obesity |
None of these numbers means much on its own, and a printout without a doctor is only a printout. At SŌMA the report is read against the patient's history, blood results and goals, and the changes to the plan are written down. That is the part the device cannot do.
What the scan adds to diagnosis
For the patient, the first benefit is a more accurate picture of risk than weight or BMI can give. Several patterns that a scale misses are common in clinic. A person of normal weight can carry a high proportion of body fat and little muscle, a state sometimes called normal-weight obesity, and a person with a high BMI can be heavily muscled with a healthy fat mass. Visceral fat can be high at a modest waist size, and it is the fat most closely tied to insulin resistance, fatty liver and cardiovascular risk. Muscle can be low for a person's age and sex long before it shows as weakness; the European consensus on sarcopenia accepts bioelectrical impedance as a method for estimating muscle quantity in that assessment. A shift in body water can masquerade as fat gain or fat loss. And phase angle gives an indication of cellular health and nutritional status that no other routine clinic measurement provides.
Each of these changes what is recommended. A normal-weight patient with high fat mass and low muscle is directed towards resistance training and protein before any aesthetic body treatment. Raised visceral fat is read with HbA1c, fasting insulin, lipids and hs-CRP from the patient's blood panel, and becomes a metabolic conversation rather than a cosmetic one. A low skeletal muscle index in mid-life is treated as a preventive priority. The scan also establishes a reference point: the second scan, and every one after it, is compared against the first, and trend lines rather than single readings drive decisions.
In the weight-management programme with Wegovy and Mounjaro
SŌMA's GLP-1 programme already required a comprehensive metabolic blood panel before the first pen. The scan now sits beside it. Before a patient starts semaglutide or tirzepatide, the baseline is recorded: fat mass, visceral fat, skeletal muscle by limb, water distribution and phase angle. The patient is then scanned every four weeks, at the same dose review where side effects, appetite and eating pattern are discussed.
The picture the doctor wants to see month to month is simple: fat mass and visceral fat falling, skeletal muscle flat or falling far more slowly than fat, extracellular water steady, phase angle holding. When that is the picture, treatment continues and the dose is titrated as planned.
When it is not, the scan changes the plan, and this is where the patient benefits most. If muscle is being lost faster than expected, the remedy is rarely the medication; it is protein, resistance training and sometimes a slower dose escalation so that appetite does not fall below what the muscles need, and the patient receives a specific protein target and a training prescription rather than a general instruction to eat more. If the scale has stalled but the scan shows fat still falling and water rising, that is a plateau in name only, and the patient is told so before losing heart. If visceral fat is falling while the scale barely moves, that is a good month regardless of what the scale says. When the patient reaches target and the taper is planned, the scan confirms that what has been kept is muscle, which matters for resting metabolism and for holding the result after the medicine stops.
One further point from clinical experience. Patients on these medicines often report that they have lost their shape as the weight comes off, and it is usually the arms and legs where the muscle has gone. Seeing the segmental numbers turns a vague worry into a specific, correctable target.
In body contouring
Body contouring is the area of aesthetic medicine with the most before-and-after photographs and the least measurement. SŌMA prefers to measure. For EMS body sculpting, which contracts the muscles of the abdomen, glutes, arms or thighs thousands of times in a session, the relevant question is whether the treated area gained muscle over the series. Segmental skeletal muscle mass answers it. For fat-dissolving injections and the other slimming treatments on the body menu, the scan gives a baseline and a follow-up for total and trunk fat, so that the result is a number rather than an impression.
It also prevents treating the wrong problem. A patient who asks for fat reduction on the abdomen but whose scan shows high visceral fat and low muscle is a weight-management or metabolic patient first and a contouring patient second. The report makes that conversation easier to have, and it spares the patient a treatment that would not have addressed the cause.
In longevity and preventive medicine: the OPTIMIZE and FUTURE-PROOF programmes
SŌMA's longevity medicine starts from the premise that healthspan is measurable. Blood work, biological-age testing and now body composition are the three measurements from which everything else follows. OPTIMIZE is built around hormones, metabolism and body composition, so the scan sits at its centre: it is how the doctor judges whether a hormone or metabolic intervention is building muscle and shedding visceral fat, or merely moving the scale. FUTURE-PROOF uses it as a longevity marker in its own right.
Three parameters do most of the work here, and each has a preventive purpose. Skeletal muscle mass, compared against age-matched reference ranges, screens for sarcopenia long before it shows as weakness, and the muscle a person carries in mid-life is a good predictor of how they will function in their seventies. Visceral fat is a cardiometabolic risk marker, read together with HbA1c, fasting insulin, lipids and hs-CRP from the patient's blood results, and rising visceral fat prompts the metabolic conversation before it becomes a blood-sugar problem. Phase angle, which rises with training and good nutrition and falls with illness and age, is a whole-body measure of cell health that can be repeated every quarter. A 2025 study of 741 Indonesian adults with central obesity, run on a seca mBCA at a teaching hospital, found that phase angle tracked with skeletal muscle index and that the extracellular water ratio tracked with fat mass index and visceral fat, a useful confirmation that these markers behave the same way in a Southeast Asian population as in the European reference data.
On a programme the patient is scanned at the start, at each quarterly review and at the annual re-assessment, and the trend lines are what the doctor acts on: a falling phase angle or muscle index leads to a training and protein plan, and sometimes a review of hormones or sleep; rising visceral fat leads to a metabolic work-up. The value to the patient is that drift is caught while it is still reversible with training, nutrition and, where indicated, treatment, rather than after it has become a diagnosis.
What the doctor adds to the printout
Bioelectrical impedance rests on assumptions, and a good clinician knows them. Hydration shifts the numbers, so patients are scanned under the same conditions each time, and a reading taken after a long-haul flight or a heavy training session is discounted. Recent meals, alcohol, the menstrual cycle and a bout of illness all move water and therefore the estimates. A single scan is a snapshot; the trend across scans is the evidence. And the numbers become useful only when they are set against the patient's blood results, goals and what is realistic for their age and starting point. That readout takes about fifteen minutes, and it is the part of the appointment the clinic considers most important.
Preparation is simple: a morning slot where possible, no heavy meal in the two to three hours before, no alcohol or hard training the night before, an empty bladder, light clothing, bare feet and no metal. Patients with a pacemaker or another implanted electronic device, and patients who are pregnant, should say so before booking; BIA is not used in those cases.
Scans are included in the weight-management programme and in OPTIMIZE and FUTURE-PROOF. A standalone scan with a doctor's readout can be booked by message.
Questions patients ask about the scan
What is the seca mBCA Ultra?
A medical-grade body composition analyser made by seca in Germany. It uses 8-point bioelectrical impedance analysis with contactless ultrasonic height measurement, takes 24 seconds, and reports fat mass, fat-free mass, skeletal muscle mass (total and by limb), visceral fat, body water and its distribution, phase angle and a bioelectrical impedance vector. SŌMA in Uluwatu is the first clinic in Bali to have one.
How accurate is it compared with a DEXA scan?
The seca mBCA's algorithms were validated in peer-reviewed studies against reference methods rather than against another BIA device: fat-free mass against the four-compartment model (R² 0.98), total body water against deuterium dilution (R² 0.98), extracellular water against sodium bromide dilution (R² 0.95) and skeletal muscle mass against whole-body MRI (R² 0.97), including in people with a BMI of 30 or more. It is not a DEXA scan and does not measure bone density, but for tracking fat, muscle and water over time it is among the most accurate non-imaging methods available, with no radiation.
Do patients lose muscle on Wegovy or Mounjaro, and how would they know?
Some, yes. In the STEP 1 DEXA substudy of semaglutide 2.4 mg, fat mass fell 19.3% and lean mass 9.7% over 68 weeks; in the SURMOUNT-1 substudy of tirzepatide, fat mass fell 33.9% and lean mass 10.9% over 72 weeks, so roughly a quarter of the weight lost was lean tissue. A scale cannot show which side of that line an individual is on. A body composition scan every four weeks can, and at SŌMA it is built into the weight-management programme.
How often should a patient be scanned?
At baseline, then every four weeks while on a GLP-1 medicine or in an active body-contouring series, and every three months on a longevity programme. Scans are taken at the same time of day under the same conditions so that the numbers are comparable.
How should a patient prepare, and who should not be scanned?
A morning appointment where possible, no heavy meal in the previous two to three hours, no alcohol or hard exercise the night before, and an empty bladder. Light clothing; shoes, socks, watches and jewellery are removed. Patients with a pacemaker or another implanted electronic device, and patients who are pregnant, should say so before booking; bioelectrical impedance is not used in those cases.
How much does a body composition scan cost at SŌMA?
Scans and the doctor's readout are included in the medical weight-management programme (from IDR 4,500,000 per month, covering the consultation, GLP-1 medication and body composition tracking) and in the OPTIMIZE and FUTURE-PROOF programmes. A standalone scan with a doctor's consultation is also available; the current price is confirmed on enquiry. All prices exclude 11% government tax.
Can a patient have a scan without joining a programme?
Yes. Many patients want a baseline before a trip, a training block or a decision about medication. The patient receives the full report, a doctor explains it, and any next step is the patient's decision.
