Just like scales don’t tell us the whole picture about your body’s health, we haven’t been getting the full story about body composition analysis…

It’s starting to become commonly accepted that scales and body mass index (BMI) are on their way out.

Why not scales or BMI anymore?

Scales tell you how much you weigh in kg or lbs and BMI is a simple calculation using your height to weight (kg/m^2).

Both measures have been used in the past by doctors, personal trainers, nutritionists, and large population studies to assess health.

However, they are not without their flaws.

For example, if you’re a bodybuilder with 5% body fat but a high muscle mass, then the number on the scale and your BMI would both be higher than it “should” be according to those measurements and you’d likely be classified as “obese”.

And, equally, you could have a “healthy range” for weight, but a higher fat mass and lower skeletal muscle mass, so a scale shows that you’re in a “healthy” range but in actuality, it’s skeletal muscle mass that’s a more important clinical target parameter vs weight in that situation (for example, in patients with chronic obstructive pulmonary disease, sarcopenia, frailty, cancer cachexia, chronic glucocorticoid therapy, and others).

Scales don’t tell the full story.

These flaws are why body composition analyzers have been invented.

Body composition analyzers indicate exactly what your body is made up of; fat mass, fat-free mass, and more — and that tells us more than simple, outdated anthropometric measurements like BMI and weight.

There’s a high degree of diversity in body composition (for example, normal fat mass or increased adiposity, gyroid or visceral obesity, sarcopenia or athletic nutritional status, normal hydration or excess body fluid) and it’s inaccurately reflected by simple anthropometric measures.

Noninvasive and inexpensive measurement of total and regional skeletal muscle is of great practical importance; detailed body composition analyses have a clinical application, research basis, and high-performance use on an individual level and have become an important tool in large-scale studies.

But a valid body composition measure isn’t easy to obtain because the measurements need to be cost-effective, non-invasive, high reproducible, convenient and easy to use.

In this context, whole-body magnetic resonance imaging (MRI) and dual X-ray absorptiometry (DXA) are considered as valid reference methods however, the use of more simple and inexpensive bioelectrical impedance analysis (BIA) has become more and more popular, and increasingly accurate based on the latest and updated technology.

The new generation of BIA devices provides very high precision and accuracy because of the…

  1. Segmental measurement of arms, legs, and the trunk that could reduce the assumptions about body shape.
  2. Accurate measurement of both resistance and reactance at a spectrum of frequencies from 1 to 1000 kHz. (Huh? Why does this matter? Keep reading, friend!)
  3. Higher precision of posture and contact to electrodes.

We’re accepting body composition technology as the new scale and they’re becoming widely used — but some of them aren’t without their flaws as well…

Let’s debunk the myths and reveal the truths when it comes to body composition analysis.

First, how does a body composition analyzer work?

Basically the way a body composition analyzer works is as a bioimpedance analysis; the human body is regarded as an electrical conductor in an alternating current circuit and its alternating current resistance (impedance) is measured.

Uhhhh, what does that mean?

Basically, the technology can determine the different tissues in your body based on how fast a low pulse travels through your body and the resistance levels.

The length, cross-section, and material properties have an impact on electrical conductors impedance. For example, for humans length means height, cross-section means waist circumference (as one measurement), and the material means body water compared to cell tissue.

Body water is a good electrical conductor (allows energy to pass easily) while cell tissue acts as a capacitor (stores energy).

Age, gender, physical fitness, and ethnicity also have an impact on impedance when it comes to the human body.

If the alternating current is applied at different frequencies, individual parameters can be specifically determined. So if low frequencies are used then the proportion of extracellular water can be determined directly because alternating current at these frequencies is hardly able to penetrate cell walls. Cell walls and intracellular water have a very minor impact on impedance.

If you measure these parameters as well as the weight, height, age, and gender of an individual the body composition of an individual can be determined and then assessed!

…doesn’t that seem too simple (good) to be true?

Yes, it does. And, well, it is.

It used to be touted that if you step on or hold any one of these machines it would spit out perfectly accurate numbers.

But with greater analysis and increases in technology, research has proven that that’s a myth.

The device set-up and formulas used to analyze the data can make or break the results given… and this is where there’s more to it.

The comparability and accuracy of formulas used to determine body composition are based on the results of what is referred to as validation studies compared to reference methods of the gold standard, so must be evaluated critically as the validation studies were performed with differing reference methods and, in all respects, heterogenous reference populations. In addition, the study results cannot necessarily be transferred to other manufacturers’ devices for technical reasons.

The variance explained by segmental bioimpedance analysis (BIA) equations ranged between 97% for total skeletal muscle mass, 91-94% for limb skeletal muscle mass, and 80-81% for visceral adipose tissue. There are no differences in results based on supine (lying down) and standing position for the test. Segmental assessments compared to conventional wrist-ankle measurements have an improved prediction. And when compared to DEXA, MRI-based BIA equations are more accurate for predicting muscle mass. But while the BIA results can correctly identify ethnic differences in muscularity and visceral adiposity, research on the comparison of bias revealed some ethnical effects on the accuracy of BIA equations. So a correction factor for certain ethnicities may be required.

Compared with conventional whole-body wrist-ankle methods, BIA measurements with an “8-electrode system” that uses a 4-electrode setup in different arrangements around the body allow for a segmental analysis of body composition.

The common belief that BIA analyzers that incorporate foot and hand contact points for standing on four metal plates and holding a rod with the fingers and thumb of each hand (eg. Seca, Tanita, Omron, or BioSpace) have significant disadvantage because of the high resistance of the body ankle and wrist (>50% of whole-body resistance) but only contribute 1.8% to body weight is now refuted. Because it uses segmental impedance measurements this technology provides a significantly better prediction compared to conventional wrist-ankle technology. And moreover, this system may, therefore, compensate for ethnic differences in body shape (eg. length and muscularity of extremities compared with the trunk) and may, therefore, be more accurate than BIA measurements based on conventional wrist-ankle technology with 4 electrodes only.

The discrepancies in the assumptions of a homogenous bioelectrical model that lead to a higher measurement error is associated not only with body shape, but also…

  • ageing (decreasing limb relative to trunk diameter)
  • obesity (apple and pear shape of body fat distribution)
  • and ethnic differences (in trunk relative to leg length and regional adiposity and muscularity).

It’s why segmental BIA was used to develop two indices that represent the relative contribution of trunk and extremities to total body conductivity and help to correct for differences in body shape.

The findings show that differences in BIA biases for a BIA equation are more device-specific than population specific. If a device applies ethnic-specific correction factors to equations for prediction of skeletal muscle mass and visceral adipose tissue it results in a more accurate prediction of skeletal muscle mass when compared to DXA.

This improvement in BIA technology has overcome previous limitations and lacking validity.

(To demonstrate the room for error, even within an MRI analysis the coefficients of variation for repeated measurements of skeletal muscle mass and visceral adipose tissue were 1.8% and 1.5% and the technical error for three repeated readings of the same scan by the same analyst for skeletal muscle mass and visceral adipose tissue was 2.4% and 1.97% respectively (coefficient of variation).)

This is why BIA technology — some more than others — has been increasingly accepted as the new gold standard for body composition analysis.

The high accuracy of the generated prediction equations can be attributed to the following reasons;

  • High reproducible positioning of the participants for the BIA measurement that is facilitated by variable handrail positions depending on the height of the person
  • 8 electrodes are used and therefore the upper body, lower body, left side, and right side of the body are assessed
  • The new indices that were developed from measured values to represent the relative contribution of trunk and extremities to total body conductivity could adjust for differences in body shape that contribute to inaccuracies in previous BIA measurements

You want to look for a body composition analyzer that has that technology.

One device; the Seca medical Body Composition Analyzer, is a phase-sensitive 8-electrode medical BIA device that covers a full range of frequencies from 1 to 500 kHz and allows a segmental analysis of the whole body. Seca collaborated with universities, institutes, research centres, and hospitals to study and develop its own predictive formulas for determining the following parameters for the arms, legs, torso, and the whole body;

  • Total body water (TBW)
  • Extracellular water (ECW)
  • Fat-free mass (FFM)
  • Skeletal muscle mass (SMM)

So what CAN a body composition analyzer like that evaluate now?

In its entirety, for example, the Seca body composition analyzer has the ability to evaluate…

ENERGY: to determine a person’s energy expenditure and energy reserves.

These parameters include;

Fat mass

Fat mass index

Energy stored in the body

Resting energy expenditure*

Total energy expenditure

*No bioimpedance measurement is required for the resting energy expenditure parameters because it’s determined with the aid of height, weight, and the automatic BMI calculation. It’s a shortfall because it’s a general population approach to analyzing resting energy expenditure but it’s not as accurate or personalized based on an individual’s metabolic rate compared to a metabolic test.

FUNCTION/REHABILITATION: to determine a person’s level of fitness and allow the success of a training regime or plan to be assessed.

These parameters include;

Fat-free mass

Fat mass

Fat mass index

Skeletal muscle mass

FLUID: to determine a person’s fluid status.

These parameters include;

Total body water (TBW)

Extracellular water (ECW)

Ratio of extracellular water to total body water (ECW/TBW) [%]

Bioimpedance vector analysis

HEALTH RISK: to provide an overview of body composition and compare the results with values for healthy people — a body composition which deviates from the normal range is an indicator which can be used to assess the risk to health.

These parameters include;

  • Phase angle
  • Visceral adipose tissue
  • Bioimpedance vector analysis
  • Fat mass index
  • Fat-free mass index

So depending on what you’re looking to evaluate you would be looking at different body composition analyzer parameters. For reference, the equations of this analyzer always show normal ranges for each parameter.

Why a bioimpedance analysis device over other body composition analysis methods?

You may have heard about DEXA (dual-energy x-ray absorptiometry) machine which can be used as a body scan in multiple different applications. DEXA uses radiation for its analysis; two x-ray beams are aimed at the bones.

The amount of radiation used during one of these scans is less than 2 days of exposure to natural background radiation (NBR). But, according to the HARP act, you need a referral from a doctor for a DEXA scan in Ontario. As well, DEXA reports on fat mass, bone mineral content, and fat-free mass, but it is not able to measure muscle mass.

Body composition analyzers such as Seca are radiation-free which means you can test more frequently without worrying about dosing and the bioimpedance devices are specifically designed to be able to measure muscle mass.

There are bioimpedance devices that you can step on or hold with your hands to give you an idea of your body composition and then there are some that you step on and hold with your hands.

So what’s the difference between them?

If the device is only attached to two limbs then it does a poor job of transmitting the pulse throughout your entire body. The more advanced technology, with four touchpoints, is segmental which means it breaks the body into regions.

Another big flaw with some machines is treating every body as though all bodies are exactly the same. They’re not, and that’s exactly why you do these assessments. But the technology needs to account for that.

The Seca machine we use, because of this proven research, has the ability to account for gender and ethnicity biases that can be found in the analysis by other machines.

As well, not all body composition machines are able to measure hydration status aka water. For example, changes in hydration measured via DEXA show up as changes in fat-free mass.

The body composition analyzers that use an 8-point method (flow of low alternating current and the measurements of impedance are performed for each side of the body using a pair of foot electrodes and 3 pairs of hand electrodes) can be analyzed based on scientifically-established formulas to determine the parameters of total body water (TBW), extracellular water (ECW), fat-free mass (FFM), and skeletal muscle mass (SMM) for arms, legs, torso, and whole body.

The current “gold standard” for body composition analysis comprises a combination of methods, some of which are highly technical and very time-consuming, for determining individual parameters. It’s been accepted that bioimpedance analysis is a method for rapid, simple, and non-invasive assessment of body composition.

Note: Google defines “gold standard” in medicine and statistics as “a gold standard test is usually the diagnostic test or benchmark that is the best available under reasonable conditions. Other times, a gold standard is the most accurate test possible without restrictions.”

What does this mean? Why would you want to know these numbers?

The results displayed graphically can assist in…

  • Determining energy expenditure and energy reserves as a basis for nutritional advice
  • Assessing metabolic activity and the success of a training program (eg. within the framework of rehabilitation or physiotherapy)
  • Determining a patient’s fluids status
  • Determining the general state of health or, in the case of a previously-known disease, assessing the severity
body composition analysis
How does this change your game?

Well, it depends on what game you’re playing.

Weight management?

Body composition analyzers display both fat mass and fat-free mass to understand what is making up the numbers on the scale.

Metabolic, “unhealthy” persons with insulin resistance often exclusively lose water weight when commencing with weight reduction so the ability to quantify water retention and assess body water over time to evaluate these effects can help with the loss of water at the beginning and then weight staying at a standstill.


The additional information with precise results (fat, water, muscle mass — not only weight) can enhance nutrition plans and optimize individual care.

For example, in a clinical application, accurate body composition measurement helps to detect cachectic states and body water (cachexia; weakness and wasting of the body due to severe chronic illness — in more than 22% of tumour patients cachexia is the immediate cause of death) and this allowed for the monitoring and adapting of nutritional state during therapy in order to reduce mortality. Edema may mask the substantial loss of fat and muscle mass so the measurement of water has to be taken into account when assessing a patient’s prognosis. When treating diabetes a reduction of fat mass while preserving skeletal muscle mass is indicated so the accurate monitoring of fat and muscle mass helps to assess a plan’s efficacy.

Sports medicine and fitness goals?

A differentiated body composition analysis can help optimize physiotherapy/rehabilitation and fitness training.

Closely monitoring changes in body composition during injury, forming rehabilitation goals, segmental analysis of muscles (arms, legs, trunk) helps to define specific physiotherapy treatment and monitor the implementation over time. The evaluation of fat and muscle mass is valuable in commencing competition training or pre-season training camps and assessing the efficacy of training plans. Experienced coaches and sport physicians may define cut-off values for specific sports or certain positions in order to optimize performance capacity. For young athletes, they often lack skeletal muscle mass as they develop and custom-made, tailored muscle development training can be applied to increase muscle performance and prevent deficits and injuries. And on the other end of the spectrum, monitoring the phase angle may evaluate overtraining and exhaustion because an insufficient recovery and inadequate supply of nutrition can cause a phase angle decrease so it results in inflammatory reactions of the body cells (increased extracellular water).

General health?

Additional information beyond weight can enhance decisions, optimize plans, and increase care.

Body composition analysis results can indicate the precursors for diabetes and arteriosclerosis in patients with obesity, deficiency symptoms for patients who are underweight, and reduced muscle mass and metabolic rates for patients of a normal weight. Evaluating body water and edema (a condition characterized by an excess of watery fluid collecting in the cavities or tissues of the body) is of vital importance in many medical fields; like nephrology, intestinal, hepatorenal, and cardiac patients. Monitoring the total body water, extracellular water, and water distribution helps to detect and control edema. The segmental analysis of the extremities (arms, legs, and trunk) can monitor muscle function which can be applied to diabetology, training management in athletes, rehabilitation, and physiotherapy.

The values are compared to normal ranges so it’s ideal for detecting clinical relevances, tracking response to treatment, detecting early signs of sarcopenia and other health precursors, and improving outcomes.

Monitoring body composition lays the foundation for individualized, proactive treatment. The results are simple to understand and easy to know precisely what changes to make to have the biggest impact. The reliable data gives insight on an individual’s health status and that helps to make treatments and plans more effective. This non-invasive assessment provides accurate, rapid results in under 30 seconds as well as an immediate overview of your health status. Individuals are then engaged in their plan and understand the best approach and how to optimize results, so it’s easily motivating to achieve your goals. Healthy body composition is the foundation for maximum performance, for preventing disease, and for feeling well.

But it is important to assess what technology and device you use to give you accurate and relevant insight for your body.

If you choose the right one, body composition analyzers can provide non-invasive, quick, accurate results for individuals and on a greater scale, its application can assist in our population’s weight loss, general health, patient care, and fitness performance.