Body Composition Assessment
Body composition assessment measures the relative amounts of fat, lean tissue and other components that make up body mass.
It is widely used in occupational health, professional fitness assessment, sports science, healthcare, rehabilitation and human performance testing.
Different methods provide different levels of detail and accuracy, ranging from practical field assessments such as skinfold measurement to professional ultrasound and body-composition systems.
Cartwright Fitness provides professional body composition equipment, assessment tools and evidence-led guidance for organisations that need consistent and repeatable measurements.
What Is Body Composition?
Body composition describes the components that make up total body mass.
Depending on the method used, an assessment may estimate or measure:
Body fat percentage
Fat mass
Fat-free mass
Lean mass
Muscle thickness
Body water
Body weight alone cannot distinguish between these components.
Two individuals can weigh the same but have very different body compositions.
Why Measure Body Composition?
Body composition assessment can help practitioners:
- establish baseline physical status
- monitor changes over time
- support health and fitness assessment
- track rehabilitation or training
- contribute to occupational fitness programmes
- support sports-performance profiling
- provide more information than body weight alone
The most appropriate method depends on the purpose of the assessment and the level of measurement required.
Body Fat Percentage
Body-fat percentage represents the proportion of total body mass estimated or measured as fat tissue.
For example:
Body mass = 80 kg
Body fat = 20%
Body-fat percentage should not be interpreted in isolation.
Professional interpretation should consider the participant, the measurement method, the purpose of the assessment and the limitations of the technique being used.
Methods of Body Composition Assessment
There is no single method that is appropriate for every professional environment.
Common approaches include:
Skinfold measurement
Ultrasound body composition
Bioelectrical impedance analysis
Anthropometry
Professional weighing and measuring systems
Each method uses a different approach and has its own strengths, assumptions and limitations.
The most important consideration is to use an appropriate method consistently.
BodyMetrix Pro Ultrasound Body Composition
BodyMetrix Pro is a professional ultrasound system for measuring body fat and muscle thickness.
Unlike traditional skinfold testing, ultrasound allows practitioners to assess tissue thickness without pinching the skin.
The system can also provide a visual representation of the tissue being measured, helping practitioners monitor changes in fat and muscle over time.
BodyMetrix Pro is particularly relevant for professional environments where repeatable body-composition measurement and progress tracking are important.
Applications include:
Health and fitness assessment
Sports performance
Personal training
Clinical nutrition
Body-composition monitoring
Professional client assessment
BodyMetrix Pro combines a portable ultrasound probe with dedicated software for recording measurements and tracking changes.
It provides an alternative to traditional skinfold assessment for practitioners who want a more advanced method of evaluating subcutaneous fat and muscle thickness.
Featured professional system
BodyMetrix Professional Ultrasound System
For practitioners who want a portable ultrasound approach to measuring subcutaneous fat and muscle thickness, explore BodyMetrix Pro.
Ultrasound vs Skinfold Testing
Skinfold and ultrasound assessments both aim to provide useful information about subcutaneous tissue, but they use different measurement methods.
Skinfold Testing
Skinfold calipers physically pinch and measure a fold of skin and subcutaneous fat at defined anatomical sites.
The measurements are then entered into a prediction equation.
Ultrasound Body Composition
Ultrasound uses a probe to assess tissue beneath the skin.
Systems such as BodyMetrix Pro can be used to measure fat and muscle thickness without physically pinching the skin.
For professional practitioners, ultrasound may provide a useful alternative when visualising and monitoring changes in tissue thickness is important.
The results from different methods should not automatically be treated as interchangeable.
Skinfold Testing
Skinfold measurement remains a practical field method used to estimate body composition.
A practitioner uses skinfold calipers to measure subcutaneous fat thickness at defined anatomical sites.
The measurements are then entered into a published prediction equation.
Depending on the protocol, the result may be used to estimate:
Body density
Body-fat percentage
Skinfold testing can be useful where a portable and relatively low-cost assessment method is required.
Jackson–Pollock 3-Site Skinfold Assessment
The Jackson–Pollock 3-site method is one of the most widely recognised skinfold-based body-composition approaches.
The protocol uses three sex-specific skinfold sites together with age to estimate body density.
Body density can then be converted into estimated body-fat percentage using an appropriate equation such as the Siri conversion.
Cartwright Fitness provides a free Jackson–Pollock 3-Site Skinfold Body Fat Calculator.
Skinfold Calipers
Professional skinfold assessment requires appropriate calipers and consistent measurement technique.
A skinfold protocol should define:
measurement site
anatomical landmarks
side of the body
number of measurements
measurement timing
caliper placement
which readings are recorded
Small differences in technique can affect the result.
For repeat assessments, the same protocol and preferably the same practitioner should be used wherever possible.
Estimated vs Measured Body Fat
This distinction is important.
Skinfold equations estimate body composition.
The result depends on:
- the measurement technique
- the prediction equation
- the population in which the equation was developed
- the participant’s characteristics
The result should therefore be described as an estimated body-fat percentage.
Other systems use different forms of measurement and modelling.
Professional reports should always make clear which method was used rather than treating every body-fat percentage as directly equivalent.
Anthropometry
Anthropometry is the measurement of physical dimensions of the human body.
Common anthropometric measurements include:
Height
Body mass
Skinfold thickness
Circumferences
Limb measurements
Body dimensions
Anthropometry is widely used in health, research, occupational assessment and sports science.
Consistent measurement technique is essential if results are going to be compared over time.
Height and Weight Measurement
Height and body mass are among the most fundamental measurements used in professional physical assessment.
Reliable measurements require suitable equipment and standardised procedures.
These measurements can also be used alongside:
Body composition
Relative strength
BMI
Aerobic fitness calculations
Professional weighing and measuring systems are particularly useful when small changes need to be tracked accurately.
Bioelectrical Impedance
Bioelectrical impedance analysis, commonly known as BIA, estimates body composition by measuring the body’s resistance to a small electrical current.
Depending on the device, outputs may include:
Body fat percentage
Fat-free mass
Muscle mass
Body water
Results can be influenced by factors including:
hydration
food intake
exercise
time of day
device type
Repeat assessments should therefore be performed under similar conditions wherever possible.
Choosing a Body Composition Method
The most appropriate method depends on what you need to measure.
For example:
Skinfold calipers may be appropriate when a portable, low-cost field assessment is required.
BodyMetrix Pro ultrasound may be preferable when practitioners want to assess fat and muscle thickness and track tissue visually over time.
Professional body-composition analysers may be appropriate when a wider range of body-composition outputs is required.
The starting point should always be:
What information do you need from the assessment?
Body Composition in Occupational Fitness
Body composition may form part of a wider occupational fitness assessment.
However, body composition should not automatically be treated as a direct measure of job capability.
The relevance of any body-composition measure depends on the physical demands of the role and the purpose of the assessment.
A professional occupational fitness programme may combine:
Aerobic fitness
Strength
Power
Flexibility
Body composition
Role-specific physical capability
Explore Occupational Fitness Assessment
Body Composition in Sport
Body composition can be relevant to sports performance where body mass, muscle mass or power-to-weight ratio influences performance.
Sports programmes may use body-composition assessment to:
monitor training adaptation
track changes over time
support nutrition planning
profile athletes
monitor rehabilitation
The most appropriate measurement method depends on the sport and the level of precision required.
Body Composition in Health Assessment
Body composition can provide useful context in professional health assessment.
For example, changes in total body mass may not show whether weight change is primarily due to:
fat mass
lean tissue
muscle
body water
Body-composition assessment can therefore provide information that body weight alone cannot.
Results should still be considered alongside other relevant health and physical measurements.
Standardising Body Composition Testing
Body-composition measurements can be influenced by technique and testing conditions.
A professional protocol should define:
- equipment used
- participant preparation
- measurement sites
- hydration considerations
- time of day
- number of measurements
- calculation or analysis method
- reporting units
For repeat testing, these conditions should be kept as consistent as possible.
Body Composition Equipment
Cartwright Fitness supplies professional equipment for body-composition and anthropometric assessment.
This includes equipment for:
Ultrasound body composition
Skinfold measurement
Professional weighing
Height measurement
Body-composition analysis
Anthropometry
The appropriate equipment depends on the method being used and the level of measurement required.
Explore Professional Fitness Testing Equipment
Seca Body Composition Equipment
Seca is a recognised manufacturer of professional medical weighing, measuring and body-composition equipment.
Cartwright Fitness supplies Seca products for healthcare, occupational-health and professional assessment environments.
Free Body Composition Assessment Tools
Cartwright Fitness provides a free professional Jackson–Pollock 3-Site Skinfold Body Fat Calculator.
The wider Professional Assessment Tools library also includes assessments for:
Aerobic fitness
Strength
Power
Flexibility
View All Professional Assessment Tools
Body Composition Assessment Batteries
Body composition is often more useful when considered alongside other physical measurements.
A professional assessment battery might include:
Aerobic fitness
→ Strength
→ Power
→ Flexibility
→ Body composition
This creates a more complete physical profile than any single measurement alone.
Explore Professional Fitness Assessment
Recording Body Composition Results
Professional organisations may need to record more than a single body-fat percentage.
A complete assessment record may include:
participant details
body mass
measurement method
measurement sites
individual measurements
calculation method
estimated or measured outcome
previous results
assessment date
This becomes increasingly important when the same participant is assessed repeatedly.
Cartwright Assess
Cartwright Assess is being developed to bring multiple professional physical assessments into one participant record.
Body-composition measurements will sit alongside:
Aerobic fitness
Strength
Power
Flexibility
within the same professional assessment platform.
The intended workflow is:
Measure → Record → Interpret → Compare → Report
Evidence-Led Body Composition Assessment
A professional body-composition result should make clear how it was obtained.
Where appropriate, Cartwright Fitness assessment resources identify:
- measurement protocol
- equipment
- measurement sites
- calculation or analysis method
- whether the result is measured or estimated
- reference population
- limitations
- supporting evidence
This helps practitioners interpret results consistently rather than treating every body-composition number as equivalent.
Professional Body Composition Assessment
Evidence & reference sources
Anthropometric methods depend on standardised landmarking, measurement technique and appropriate interpretation. Recent review evidence highlights meaningful differences between skinfold protocols, while ISAK maintains international standards and accreditation for anthropometric assessment.
Skinfold measurement protocols and standards: review ISAK international anthropometry standards
Cartwright Fitness provides the equipment, assessment tools and software infrastructure needed to support professional body-composition testing.
The starting point should always be:
What do you need to measure, and what level of measurement is appropriate?
From there, practitioners can select an appropriate method ranging from field-based skinfold assessment to professional ultrasound systems such as BodyMetrix Pro.
The objective is not simply to generate a body-fat percentage.
It is to create a measurement that is consistent, interpretable and appropriate for the purpose of the assessment.