BCM
Body Cell Mass (BCM)
Body Cell Mass is defined by the manual as intracellular water plus protein — the part of the body made up of the cells of your own tissues.
Short answer
Body cell mass is intracellular water plus protein, that is fat free mass stripped of water outside the cells and of bone. It is useful above all where extracellular water is raised and fat free mass might therefore look better than the true state of the tissue.
- Body cell mass (BCM)35.9 kg
- Extracellular mass (ECM)18.8 kg
What the value represents
Fat free mass also contains water outside the cells, bone and other tissue that does not itself work metabolically. Body cell mass is an attempt to filter that part out and leave only what the cells consist of: their internal water and their protein.
The manual defines it directly as the sum of intracellular water and protein and calls it the total amount of cells that make up tissue.
The practical point lies in what the value leaves out. The manual recommends it as an indicator for nutritional assessment precisely where fat free mass or BMI could be distorted — in older adults and in people with oedema, fluid retention or ascites, where extracellular water is raised and fat free mass is overhydrated. The measurement itself, though, does not establish nutritional status.
- The mass of the cellular component of the body in kilograms: intracellular water and protein.
- The part of fat free mass made up of your own cells, without extracellular water and without bone minerals.
- A companion to fat free mass in situations where extracellular water is raised.
- It does not represent the number of cells, their function, or nutritional status as a diagnosis.
How the value is produced
- A calculated value under the relationship BCM = intracellular water + protein.
- Intracellular water is derived from measured impedance; protein is calculated and the manual gives no equation for it. The uncertainty of both inputs therefore propagates here.
- The complementary quantity is extracellular mass, which the manual defines as fat free mass minus body cell mass. Their ratio appears on the result sheet as ECM/BCM.
- On the Evaluation Result Sheet, T-scores and Z-scores against manufacturer data are shown for body cell mass according to the catalogue.
- The reference range in brackets is a comparison against a reference; the manual does not publish the formula for it.
How to read the current value
- Read the value against the reference range in brackets. Absolute kilograms cannot be compared between people — a larger and more muscular person naturally has more cell mass.
- The manual gives no threshold or interpretive bands for this value. Work with the range on your sheet and with the trend rather than inventing thresholds.
- More useful than the absolute value is the ratio of cell mass to extracellular mass (ECM/BCM). A shift in that ratio describes a change in the balance between the cellular and non-cellular components.
- T-scores and Z-scores on the evaluation sheet express position relative to the manufacturer reference set, not to a clinical norm.
How to read change over time
- Body cell mass changes more slowly than body water alone, because the protein component grows and falls with tissue. Follow it at intervals of months.
- A rise together with a rise in muscle mass, protein and intracellular water is a consistent picture of a real gain in tissue.
- A fall in cell mass while fat free mass holds steady or rises means the balance has shifted towards the extracellular component. Check the ECW/TBW and ECM/BCM ratios.
- During weight reduction, holding on to cell mass is a more favourable signal than merely holding fat free mass, because the latter can also be preserved by retained water.
General principles: how to read change between measurements →
What to read it with
- Intracellular water and protein – the two components body cell mass consists of.
- The ECM/BCM ratio – expresses the relationship between the extracellular and cellular parts of fat free mass.
- The ECW/TBW ratio – shows whether water has shifted into the extracellular space.
- Fat free mass – the parent quantity that body cell mass gives a complementary view of.
- Phase angle – another indicator tied to the state of cell membranes.
- Skeletal Muscle Mass – the main tissue in which cell mass is contained.
Common misunderstandings
- Body cell mass is not a count of cells. It is their estimated mass in kilograms.
- It is not a nutritional diagnosis. The manual recommends it as an indicator for nutritional assessment, but the assessment is made by a professional, not by the device.
- It is not the mass of your organs. It covers the cellular component of all tissues, including muscle.
- A higher value is not automatically better. It makes sense to interpret it against the reference range and in relation to extracellular mass.
What can affect the result short term
- Hydration status, because intracellular water is the main component of the value.
- Training shortly before the measurement, which changes perfusion and fluid distribution.
- Food and drink before the measurement; the manual recommends measuring fasted.
- Time of day and body position before the measurement.
- The quality of electrode contact and correct posture during the measurement.
- The menstrual cycle, during which body water fluctuates.
What to do next
- Use body cell mass as a companion to fat free mass wherever you suspect the latter could be distorted by retained fluid.
- Always open the ECM/BCM ratio and the ECW/TBW ratio alongside it. The kilograms alone carry less information than their distribution.
- Follow it at intervals of months together with muscle mass and protein. The three together describe the development of active tissue.
- Take nutritional questions to a nutrition professional or a doctor. The value is an input to an assessment, not its outcome.
What the value does not determine
- It does not diagnose malnutrition or any other condition.
- The manual gives no thresholds or interpretive bands for it.
- It shares the uncertainty of both the intracellular water estimate and the protein calculation, for which the manufacturer gives no equation.
- It is not among the parameters validated against DEXA in the manufacturer internal study.
- Values are not interchangeable between devices or methods.
On terminology
- The manual gives body cell mass as an indicator used in nutritional assessment. It is neither the assessment itself nor a diagnosis.
- Extracellular mass (ECM) is defined as fat free mass minus body cell mass — not to be confused with extracellular water (ECW).
When to discuss it with a professional
Unintended weight loss, swelling or a sustained decline in body cell mass belong with a doctor or a nutrition professional. The measurement does not establish these states.
In more depth, with sourcesIn more depth: why BCM complements fat free mass where fat free mass failsExpand the detailed explanation
Fat free mass is the sum of body water, protein and minerals, and therefore also includes extracellular water and bone minerals — tissue that is not itself metabolically active cells. The manual therefore defines body cell mass as intracellular water plus protein, and additionally introduces extracellular mass as fat free mass minus body cell mass. The ECM/BCM ratio then describes how lean tissue divides between the two parts.
The manual explicitly recommends body cell mass as an indicator for nutritional assessment in older adults and in people with oedema, fluid retention or ascites. The reason is structural: in these states extracellular water rises, fat free mass is overhydrated and can look preserved even as the cellular component declines. The ESPEN clinical guidelines on bioimpedance point to the same limitation in general terms when they name altered fluid distribution as a situation in which body composition estimates are less reliable.
Body cell mass shares its physiological basis with phase angle, which the manual defines as the arctangent of the ratio of reactance to resistance and links to cell mass and the structural integrity of membranes. Expert reviews of phase angle use it precisely as an indicator related to cell mass and membrane state. The two values therefore complement each other well: cell mass describes quantity, phase angle describes electrical properties. Neither on its own establishes nutritional or health status.
Sources
- InBody 970 Result Sheet Interpretation (ENG_A_211104) — InBody Co., Ltd.
- Bioelectrical impedance analysis – part II: utilization in clinical practice — Clinical Nutrition (ESPEN guidelines)
- Bioelectrical phase angle and impedance vector analysis – clinical relevance and applicability — Clinical Nutrition
On this page
Related values
Related articles
Where to find it
The first table at the top of the result sheet, labelled Body Composition Analysis.
- Reviewed by
- MojeInBody content team
- Date
An InBody measurement is not a diagnostic tool. Results do not determine health status and do not replace a medical examination.
FAQ
Frequently asked questions
Answers to what people ask most often about this value.
What is the difference between body cell mass and fat free mass?
Fat free mass covers body water, protein and minerals — including water outside the cells and bone minerals. Body cell mass, per the manual, is only the sum of intracellular water and protein, that is the cellular component of tissue.
Why does the manual recommend BCM in older adults and people with oedema?
Because in these states extracellular water rises, and fat free mass as well as BMI can look better than the true state of the tissue. Body cell mass leaves extracellular water out, which makes it more informative in that situation.
What BCM value is fine?
The manual gives no thresholds or interpretive bands for body cell mass. You can orient yourself by the reference range in brackets on your sheet and by your own trend under comparable conditions.
Explanations make the most sense alongside your own trend.
The public guide is open to everyone. The client portal adds your own value, history and the context of a specific measurement.