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  • Writer's pictureDr Shawn M. Carney

Body Composition Testing, BIA (and why they tell you more than your bathroom scale)!

With the modern understanding that body fat is metabolically active and a component of the neuro-endocrine-immune system, this non-invasive and inexpensive testing sheds light on risk of diabetes, heart disease, hypertension, inflammation and even associations with fatigue and thyroid disease.

natural treatment weight management body composition bia

'Bioelectrical Impedance Analysis' or 'Bioimpedance Analysis' (BIA) is a method of assessing your “body composition”— the measurement of body fat in relation to lean body mass. This can identify some far-reaching aspects of health or disease, by evaluating metabolic rate and status, cellular health, body hydration, and more.

The Trouble with that Tummy

Research has shown that body composition is directly related to health, with higher rates of fat or adipose tissue associated with multiple adverse consequences. A normal balance of body fat is associated with good health and longevity. Why? Because body fat is more than just the storage of excess calories. Body fat is metabolically active tissue which produces inflammatory cytokine messengers including IL-1, IL-6 and TNF-alpha, thereby potentially contributing to heart disease, insulin resistance, Type 2 diabetes, or other chronic illnesses. (1) In fact, one study with almost a thousand participants concluded "... we found that fat-free mass was lower and fat mass was higher in acutely ill and chronically ill patients than controls". (2) And the National Cancer Institute lists excess weight as a risk factor for several types of conditions:

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How Do BIA and Body Composition Testing Work?

BIA is much more sophisticated than your bathroom scale, but just as simple — and almost as quick.

The analyzer measures your tissue and fluid compartments— using an imperceptible electrical current passed through pads placed on your hand and foot, and crunching those values through mathematical algorithms developed which consider a person's height, weight, sex, age, and physical activity level. (5) The test is performed as the subject lies comfortably clothed on an exam table and repeated every four weeks over several months.

The basis for this technique is that in the body, highly conductive lean tissue contains large amounts of water and conducting electrolytes, which brings with them a LOW RESISTANCE electrical pathway. Fat and bone, on the other hand, are poor conductors and therefore HIGH RESISTANCE substances, with low amounts of fluid and conducting electrolytes present. Another value called 'reactance' is also measured, and can be thought of as the opposition to the prompt flow of electric current.

With these measurements secured, the calculations will provide insight into nearly a dozen values, all specific to that person's body and age. Some of the results generated are:

  • Fat - Well known as an energy storage mechanism of the body, it has more recently been re-defined due to its neuro-endocrine-immune system roles as pro-inflammatory and contributing to many chronic diseases.

  • Fat-Free Mass (FFM) - This value is literally, what would be left after all fat was removed from the body. Many people also refer to FFM as Lean Body Mass (LBM).

  • Total Body water (TBW) - TBW is literally the measurement for all water in the body, since fat is essentially 0% water, TBW is entirely contained in the FFM.

  • Intra-Cellular Water (ICW) - This is the portion of TBW that is located within the body's cells. Often, increases in this value are associated with improved nutrition status, mitochondrial function, and increased cell health.

  • Extra-Cellular Water (ECW) - As you may suspect, this is the portion of TBW located outside the body's cells. Examples of where ECW is found include, but are not limited to: blood plasma, spinal fluid, joint fluids, and edema. Increases in this compartment are sometimes associated with mineral imbalance, increased concentration of toxins in the extracellular space, and reduced cell health.

  • Body Mass Index (BMI) - A person's BMI is equal to their weight in kilograms divided by their height in meters, squared. BMI is commonly used as an indicator of whether someone is overweight. It is important to note, however, that somebody who is 'overweight' may not necessarily be 'over-fat'. A 5'10", 300lb couch potato and a 5'10", 300lb bodybuilder will have exactly the same BMI.

  • Basal Metabolic Rate (BMR) - This value calculates the number of calories a person will use per day, by virtue of simply being alive, lying still, and breathing.

  • Phase Angle - Technically, the phase angle is the angle between impedance and resistance. It is normally expressed in degrees and infers back to cellular health, providing information on the cell membrane potential at the tissue level. Lower phase angles appear to be consistent with low reactance and either cell death or a breakdown in the selective permeability of the cell membrane and lowered bioenergetics at the cellular level; these are undesirable. Higher phase angles appear to be consistent with high reactance and large quantities of intact cell membranes and body cell mass. Phase angle changes with sex and age. Studies with burn victims and sickle-cell disease have shown its ability to evaluate cell membrane function while changes in this value have been observed in trauma, sepsis and even cancer!

Preparation for the BIA and Body Composition Testing

This test is performed in a clinician's office and requires only nominal considerations when preparing to have it done. Remember the conductive medium in the body is water so standardizing pre-test preparation will reduce the influence of temporary hydration or dehydration on test results. Hence the preparation steps pretty much come down to refraining from activities which would dehydrate the body tissues, and thus skew a person's readings toward higher levels of fat and adipose tissue. The preparation checklist includes:

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  • Not exercising or being in a sauna within 8 hours of the analysis

  • Women not having their period when scheduled for the procedure

  • No consumption of caffeine or alcohol for 12 hours prior

  • refrain from use of body lotion, activities that induce sweating or would otherwise make the skin damp

  • Drink 2 to 4 glasses of water 2 hours prior to taking the test. You may void as needed.

  • Try to have subsequent measurements taken as close to the same time of day as possible

Beyond Fat and Muscle, BIA Illustrates Complex Endocrine Metabolic Dysfunctions

Specifically the phase angle, as explained above, can show derangement at the cellular level, though it is an indirect measurement in this application. Take for example, how a change in phase angle was the strongest predictor of poor prognosis among hemodialysis patients. (6) And of interest to the many people suffering from subclinical thyroid disorder, where their dysfunction is not pronounced enough to show on commonly run lab testing, another study showed that patients with both overt and subclinical thyroid disease had altered phase angle and BIA values. (7)

These values can thus spur treatment that otherwise may have been overlooked, as well as then be retested and point to the efficacy of such treatment. For those patients that wonder:

'How will I know these supplements are helping me?', an improved phase angle could be the answer you are looking for!

Check out our website page and learn more about body composition testing and BIA offered at Northeast Natural Medicine as part of our Firstline Therapy program!


  1. Zoico E, Roubenoff R. The role of cytokines in regulating protein metabolism and muscle function. Nutr Rev. 2002 Feb;60(2):39-51. doi: 10.1301/00296640260085949. PMID: 11852969.

  2. Kyle, Ursula G et al. “Body composition in 995 acutely ill or chronically ill patients at hospital admission: a controlled population study.” Journal of the American Dietetic Association vol. 102,7 (2002): 944-55. doi:10.1016/s0002-8223(02)90216-6.

  3. National Cancer Institute. Cancer Trends Progress Report. Prevention. Weight. Accessed 01-25-24.

  4. Heber D, Ingles S, Ashley JM, Maxwell MH, Lyons RF, Elashoff RM. Clinical detection of sarcopenic obesity by bioelectrical impedance analysis. Am J Clin Nutr. 1996 Sep;64(3 Suppl):472S-477S. doi: 10.1093/ajcn/64.3.472S. PMID: 8780366.

  5. Oldham, N M. “Overview of bioelectrical impedance analyzers.” The American journal of clinical nutrition vol. 64,3 Suppl (1996): 405S-412S. doi:10.1093/ajcn/64.3.405S.

  6. Maggiore, Q et al. “Nutritional and prognostic correlates of bioimpedance indexes in hemodialysis patients.” Kidney international vol. 50,6 (1996): 2103-8. doi:10.1038/ki.1996.535.

  7. Seppel, T et al. “Bioelectrical impedance assessment of body composition in thyroid disease.” European journal of endocrinology vol. 136,5 (1997): 493-8. doi:10.1530/eje.0.1360493.

The content and any recommendations in this article are for informational purposes only. They are not intended to replace the advice of the reader's own licensed healthcare professional or physician and are not intended to be taken as direct diagnostic or treatment directives. Any treatments described in this article may have known and unknown side effects and/or health hazards. Each reader is solely responsible for his or her own healthcare choices and decisions. The author advises the reader to discuss these ideas with a licensed naturopathic physician.


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