Bioelectrical Impedance Analysis: Understanding your measurements

Last month, we launched our first advanced body composition analyser, the MA601. This sophisticated Bioelectrical Impedance Analysis (BIA) scale has been developed by our partners Charder and provides detailed body/fat/muscle measurements.

But what do the readings mean, and how can a BIA scale help you achieve fitness goals more easily? This blog post is an overview of what your readings are telling you.



Please note that this blog post is for general information and that all individuals should seek advice from appropriate qualified medical or fitness professionals.

Before you use the MA601

- For readings to be accurate, please ensure that the scan is carried out with shoes and socks off.

- Do not touch the user during the scan as this could affect the results.

- The user should use the bathroom before using the scale but should not carry out a workout beforehand.

- It’s also recommended that the user doesn’t consume any food or drink for two hours before the measurement.

Understandably, the scan is prohibited for those with electronic medical devices, such as pacemakers. Bioelectrical Impedance Analysis scalesa are also not recommended for those who are pregnant, have a prosthetic or amputation, have embedded metal or are under the age of 6, as this can provide inaccurate results.

Bioelectrical Impedance Analysis readings from the MA601

Using the MA601 takes a couple on minutes. You'll then be able to print out your results. We'll reference the print-out as we take you through the measurements and what they mean.

The entire results sheet can be viewed in full at the bottom of this guide.

Body Composition Analysis

At the top of the results page, you will immediately see the breakdown of the Body Composition Analysis. The human body is composed of a variety of factors that can be calculated and measured; the MA601 breaks this down into the four key parameters (water, protein, minerals, and fat), as these are considered the gold-standard for medical and fitness evaluation.

Total Body Water (TBW)

Total Body Water refers to the water contained in the tissues, blood, bones, and elsewhere in the body. This parameter is a good indicator of good body health, as it shows how hydrated the body is. The body needs water for transporting waste, helping organs to function, regulating body temperature, and digestion.

For an adult female, the ideal percentage is between 45% and 60% of body weight. An adult male should have between 50% and 65% Total Body Water.

TBW can also be divided into Intracellular Water (ICW) and Extracellular Water (ECW).

Intracellular Water (ICW)

Water that is located inside your cells is called Intracellular Water. This type of water plays an important role in allowing molecules to be transported to different organelles inside the cell. In a healthy person, intracellular water should make up two thirds of the Total Body Water. The other third should be made up of Extracellular Water (ECW).

Extracellular Water (ECW)

Water found outside of cells is called Extracellular Water, which helps tissue to function well. Nutrients are served to membrane-bound cells via extracellular water, such as sodium, potassium, calcium, chlorides and bicarbonates.

Body Water Analysis

For healthy users, the ICW:ECW proportion should be roughly 3:2. A normal range for these figures can be viewed on the right hand side of the Body Composition Analysis table.

An increased amount of ICW can signal a positive change in your body composition. When muscle cells become larger, they require more ICW in order to power their cellular functions. Increased ICW contributes to an increased lean body mass and can lead to an improved Basal Metabolic Rate (BMR), increased strength and a better immune system.

An increase in extracellular water can cause excess weight and swelling in your limbs. Imbalances may cause symptoms such as decreased mental alertness, nausea and dizziness or result in high blood pressure.

According to researchers, increased extracellular water is a key element in increased body fat. An increase in body fat is accompanied by an increase in extracellular water as well. In other words, body fat lacks adequate amounts of intracellular water.

Edema Index

The ICW and ECW results can then be used to calculate the Edema Index (EI). Kidney disease or inflammation, for example, could result in a high EI, so this is useful to identify risk.

The Edema Index calculation is ECW/TBW. The Edema Index result should ideally lie between 0.36 and 0.39.

Soft Lean Mass (SLM)

Soft Lean Mass is calculated by adding together TBW and Protein. This excludes the minerals that are found in the bones, which is used to calculate the Fat-Free Mass. The more lean body mass you have, the higher your metabolism is likely to be. Having a healthy percentage of lean body mass may make you less likely to become sick or to develop health problems such as heart disease or diabetes. Having a low lean body mass, however, may increase the risk of side effects from medications.

This should generally be between 60% to 90% of body weight.

Fat-Free Mass (FFM)

Fat-Free Mass is the difference between weight and fat mass. It is calculated by adding TBW, Protein and Minerals. A Fat-Free Mass of around 10-12% for men and 20-32% for women is ideal.

Body Fat Mass (BFM)

The Body Fat Mass is calculated by subtracting the Fat Free Mass (FFM) from the total body weight. BFM is the total mass of fat in the body and is useful for identifying the effectiveness of a training programme. The Normal Range is defined according to health risks and differing body composition, as women have higher body fat ranges than men. Body Fat Mass levels should be maintained to stay within the “Normal” range.

Muscle - Fat Analysis

This section is used to compare the body’s Total Body Weight, Skeletal Muscle Mass (SMM) and Body Fat Mass (BFM).

Skeletal Muscle Mass (SMM)

Skeletal Muscles Mass consists of three major muscle types: cardiac, skeletal and smooth.

SMM correlates with athletic performance, as it is under voluntary control and is used to power movement. This makes it a popular variable to track, as it is a good indicator for muscle gains and progress. When SMM is insufficient, joints bear a significant burden due to body weight, increasing the chance of injury.

It’s also worth noting that the higher the SMM, the better it is for the body. So, the “Over” result on this table should be referred to as “overachieving” for SMM, rather than “over the recommended amount”. In fact, we recommended training to reach the “Over” SMM level.

Obesity Analysis - Percentage Body Fat (PBF)

Body fat percentage is the proportion of fat mass compared to everything else (bones, muscles and water). This is useful for determining the specific cause of weight loss or gain.

Body Fat Percentage gives a good indication of body health, because it measures body fat and excludes other elements, such as water and muscle. Unlike Fat Mass, where a healthy reading will be different for everyone – because everyone has a different body weight – it is much easier to set yourself goals with Body Fat Percentage.

In this section, PBF is shown in correlation to different body types. A PBF that aligns with either an Overfat or Obese body type, means that there is increased risk for obesity-related diseases, such as diabetes or metabolic issues.

Visceral Fat Level (VFA)

Visceral obesity can occur even if a user's weight or BMI is within standards. If this occurs, it means a person may appear thin on the outside, but actually contain fat on the inside. Visceral fat level is used as an indicator for risk of obesity-related disease, and a level under 10 (low risk) is recommended.

Body Mass Index (BMI)

BMI is the most commonly used method of determining overall body health and whether a person is overweight or not. BMI is calculated by taking into account a person’s weight in kilograms divided by the square of their height in metres.

However, high-muscular users are often defined as “obsese” according to BMI, as BMI only uses weight and height and cannot distinguish between muscle and fat. This is why we recommend using the PBF figures.

As with the PBF, the user’s BMI is compared to different body types. These ranges are determined by the World Health Organisation (WHO), according to the risk of developing obesity-related disease.

Segmental Lean and Fat Analysis

Muscle imbalance may not be particularly noticeable in day-to-day life, but it’s a critical factor when it comes to high-intensity training, health, and exercise. Most clients work out to “look good” –but if the body scan indicates a left/right or upper/lower imbalance, we recommend first strengthening weaker segments to reduce risk of injury.

Once body muscle is balanced, risk of injury is decreased. At this point, training “for health and to minimize injury risk” can transition into training to “look good”.

The pentagon on the left represents the lean mass and the pentagon on the right represents fat mass. It’s important to know that the radar chart is affected by the proportion of muscle and fat in each segment. As such, when muscle increases, fat decreases in proportion, and vice versa. Therefore, it’s important to read the total kilograms of each section, in addition to looking at the percentage results. This means that, if a body is higher in body fat, then the black lined pentagon will be larger on the right hand chart.

By calculating this breakdown by segment, the scale can accurately generate results, in comparison to handheld or stand on scales, which estimate the rest of the body.

This is also related to the Body Balance Evaluation, which can be viewed at the top of the grey box on the right hand side of the page.

Body Type Analysis (BTA)

The Body Type Analysis table compares the user’s BMI to their PBF to determine the source of their weight, which is then plotted on this graph to categorise the user’s body type.

The benefits of doing this, is that the user can then see if they have hidden obesity. Thin fat, for example, is a person who has a relatively low body weight, which is made up predominantly of fat. So while they may appear thin on the outside, they are not actually healthy.

This table simplifies the post-examination stage, by showing the user exactly how they need to improve. If a person is “Over Fat”, then they need to reduce fat and build muscle, for example.

Body Balance Evaluation (BBE)

The Body Balance Evaluation covers how well-balanced your body is. Imbalances in different body segments can increase the risk of injury or posture-related health issues.

This section consists of a number of tick boxes. As is to be expected, a user should ideally have ticks across the top of the columns to show that they have a well-balanced body. However, if a section of the body is less developed than the other body, it can create an imbalance. By calculating the differences in mass between the arms, legs and the upper-lower body difference, clients can develop goals/targets for their future training.

Muscle Quality

At the bottom of the sheet is a small section on Muscle Quality. Muscle Quality combines variables such as gender and phase angle (more on that later) to estimate grip strength. Grip strength is a general indicator for muscle quality, and is useful in tracking, evaluating and improving physical fitness programs.

However, two people who have muscles of the same size, may not have the same muscle quality. One person may be stronger than the other, despite their muscles being the same size. This is because your muscles consist of two types of tissue.

Contractile tissue contracts and produces force, whereas connective tissue keeps the muscle together. Fat is also present in a muscle. The more contractile tissue a muscle consists of, the stronger it is and the higher the muscle quality is.

A good muscle quality score depends on your age and gender; we’ve summarised these ideal scores in the table below.

As you can see, muscle development is important for everyone. Most people train to improve muscle mass (which isn’t a bad thing!), but trainers can use the Result Sheet to help demonstrate that strength training to improve muscle quality is also very important.

Basal Metabolic Rate (BMR)

Basal Metabolic Rate is the number of calories burned by the body when you’re doing absolutely nothing. These calories are used for the body’s vital functions, such as breathing, blood circulation, brain function, cell growth and the regulation of body temperature.

The BMR is correlated using the FFM and Lean Mass figures, as a higher BMR requires more calories to sustain. The average woman can expect to have a BMR between 1,200-1,600 calories a day, whereas a man can expect a BMR between 1,600-2,000 calories a day.

The key benefit of knowing the BMR is that it can help the user to set an accurate, realistic calorie goal. The BMR rate is a calculation of the minimum amount of calories your body needs to function. It is based on the number of calories the body would need if resting for 24 hours. However, a person is not inactive for a full 24 hours, so this should be viewed as a theoretical calorie expenditure.

Total Energy Expenditure (TEE)

The Total Energy Expenditure is calculated for a normal day without significant activity. However, this is not exact and should not be viewed as such; actual energy expenditure will vary depending on a person’s Physical Activity Level (PAL) and their BMR.

Phase Angle

Bioelectrical Impedance Analysis (BIA) is typically about the quantity of certain things, however two similar users may not be equally healthy. Phase angle is an indicator of overall health, metabolic activity and nutritional status. Basically, people with healthier muscles/body cells have a younger body age, which results in a higher phase angle.

The higher the phase angle is, the healthier your body is. Typically a man will have a higher phase angle than a woman, and a phase angle tends to decrease with age. However, if your client is training hard then their phase angle should gradually increase. If it steadily decreases, then that may be a sign that something is wrong with the body.

It’s important to remember that a phase angle will change from person to person, so you should compare your phase angle with your previous readings, rather than someone else’s. Generally though, the phase angle range should be between 1 to 20 degrees. Typically it will be between 4.5-6.7 for males and 4.0-6.0 for females, but this will decrease as you age.

Certain factors can influence someone’s phase angle (such as their age, gender, and BMI), but there are also considerable differences between phase angle reference values across different populations. These differences are not only explained by age or BMI and may be due to differences between impedance analyzers.This means that phase angle values tend to differ based on the BIA device you’re using.

Below are two charts to help with your understanding of phase angles. There is one for males and one for females, so make sure you're looking at the correct chart.

Female Phase Angle Chart

Male Phase Angle Chart

Fat-free Mass Index (FFMI)

Fat-Free Mass Index (FFMI) and Skeletal Muscle Index (SMI) are conceptually similar to BMI, but they are more precise. The difference is that instead of total body weight, fat-free mass (FFM) and skeletal muscle mass (SMM) is used to distinguish the source of weight.

The Fat-Free Mass Index is used to evaluate the risk of a user being malnutritioned. For men, we recommend that this figure is higher than 16.6 kg/m2 and for women we recommend that this is higher than 12.9 kg/m2. These are the cut-off points.

Skeletal Muscle Index (SMI)

The Skeletal Muscle Index is the ratio of muscles in a user’s arms and legs in comparison to their height. It is used to evaluate the risk of Sarcopenia - the generalized loss of skeletal muscle mass and strength with age. In older people this has substantial tolls in terms of morbidity and disability.

Men should aim to have a score higher than 7.5kg/m2 to be within a healthy range. For women, the score should be higher than 5.67 kg/m2.

Health Score

Most of the individual output parameters on the Result Sheet have reference ranges, but to truly evaluate someone’s overall body composition status, you need to combine parameters and analyse the numbers together. The health score combines several output parameters, including fat-free mass, skeletal muscle mass, and body fat percentage to calculate an overall health score.

The Health Score figure is not the same as the Muscle Quality Score.

A normal health score should be between 70-80, anything lower than a 60 is considered a health risk. A health score between 80-90, implies that the user participates in regular physical activity. Usually, only a professional athlete will achieve a health score of 90+.

A low score is most commonly due to insufficient muscle, or too much fat (dangerously low levels of fat will also reduce the score, though this is uncommon). Trainers can examine the Result Sheet and explain that increasing muscle/reducing fat will help improve body composition, and thus health score. With effective training, clients will see their health score improve, creating motivation to persevere.

Control Guide

The Control Guide is basically the recommended next steps for the user by providing clear number goals. The Control Guide’s recommendations are defined by the needs of the athletic population (or those striving to become more fit), and not the “average person”. As such, there may be some differences between the Control Guide (fitness-focused, higher standards) and the Muscle-Fat Analysis, which uses normal ranges based upon BMI and body fat percentages relevant to the average population.

The target control shows the ideal weight of the client. This is generated using factors such as their current weight, their BMI and their fat percentage.

The weight control shows the difference between their actual weight and their target weight. Even if the actual weight is the same as the target weight changes may be recommended, for example due to a higher than recommended fat percentage.

Fat control and muscle control show the recommended increase/decrease in the respective areas.

Impedance

The MA601 measures the impedance, reactance and resistance of the five sections used on the Segmental Lean and Fat Analysis. These are right arm (RA), left arm (LA), trunk (TR), right leg (RL) and left leg (LL). 3 different frequencies are used as they have different properties when travelling through the tissue.

For example, lower frequencies do not have enough "power" to penetrate cellular walls, and go around it. Higher frequencies, on the other hand, can go through. By combining this data, we can more accurately calculate extracellular and intracellular water, as opposed to simply "total body water", like single-frequency devices.

In other words, more frequencies are more data for the algorithms to use for improved accuracy.

Further information

If you're an MA601 user, and you need further information about the measurements the scale provides, please message the Marsden team here.

If you use the Marsden MBF-6000 or or MBF-6010, use our guide to the measurements they provide which you can read here.

You can order your own Bioelectrical Impedance Analysis scale, the MA601 Advanced Body Composition Analyser here.

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