When selecting a method, the following factors should be considered:
Research question and clinical application:
- Which body composition variables are to be quantified
- Clinical significance of these body composition compartments
- Desired level of accuracy and precision
- Validity of the method in the specific study population
- Availability of reference data for comparison
Feasibility and Resources:
- Number of participants and amount of time available
- Number and frequency of repeated measurements
- Level of participant burden and (dis)comfort
- Cost and availability of the equipment
- Staff skills, training and supervision
The tables below show practical and technical considerations as well as a selection schema based on study design, population of interest, measurements type and location of the mostly used methods available in field or laboratory settings.
Table 1. Practical and technical considerations when selecting a method
|Infrastructure||Some measures||Some types||Depends on site||✔||x||✔||x||✔|
|Quality control||✔||x||✔||✔||Up to 6 months*||-||-||✔|
Table 2. Decision schema for choosing a method based on study design, population, measurements type and location
|Fat & Lean tissues||x||FM + FFM||FM + FFM||x||FM + FFM||✔||FM + FFM||✔|
|Fat Distribution||Some measures||Some types||Depends on site||✔||x||✔||x||✔|
|< 5 Years||✔||x||✔||✔||Up to 6 months*||-||-||✔|
|≥ 5 Years||✔||✔||✔||✔||✔||✔||✔||✔|
✔ suitable, - limitations, x not suitable
FM = Fat mass, FFM = Free fat mass
*Not feasible from 6 months to 5 years old
Methods shown are the most frequently used
The first table summaries the practical and technical considerations such as cost, compliance, infrastructure, precision, quality control, training requirements and safety.
Cost includes the initial capital outlay to purchase the equipment and the costs associated with maintenance, servicing, data acquisition, which may include specialised staff, or consumables needed to perform the tests as well as cost of data analysis.
Procedures such as DEXA, and in particular the criterion method MRI, may have the highest degree of measurement accuracy, but are more expensive due to initial and ongoing costs required to support the equipment. With these techniques, participants are also required to be tested in a clinical/laboratory-based setting. Measurements of body composition obtained with BIA or skinfold thickness, have considerably lower costs associated with initial equipment purchases, and they may be more cost effective, especially for large scale epidemiological studies or studies requiring extensive follow-up. A Less cost-prohibitive method, with a high level of measurement accuracy is the deuterium method. However, compliance might be an issue due to urine samples collection and analysis.
DEXA or ADP measurements are also challenging to implement in pediatric populations, as participants are required to stay still during these procedures. In this age group, anthropometry and skinfolds are probably more practical.
In younger adults, DEXA, ADP and deuterium are accurate and precise methods when compared to the reference method 4-component model as the coefficients of determination (the R²) is between 0.95 and 0.98 (19). While, the BIA method has lower
accuracy compared to those tools as BIA is significantly affected by hydration status, Therefore instructions to participants, prior to the test are highly recommended to enable valid outcomes. Another important consideration when selecting a method
is safety . For example, DXA emits a low level of ionizing radiation and ethics committees may not permit repeated testing in young children within short periods of time.
infrastructure is also an important factor. Conventional anthropometry and devices with their own power source (e.g. BIA and portable ultrasound) are suitable tools for remote field-testing (where no access to powers source is available). Methods such as DEXA, ADP, MRI and deuterium require a clinical/laboratory-based setting with controlled ambient conditions and access to power sources. For DEXA, MRI and deuterium, specially trained technical staff are needed. The Ultrasound method is a safe procedure and systems are often portable and therefore this tool can be used in both clinical and field settings.
The second table shows a decision schema that provides a structure for choosing a body composition method with respect to population, study design, body region of interest and age of participants. We need to remember that the pragmatic needs of large scale
epidemiological studies differ from those of smaller scale clinical research. Hence, before selecting the method, consider the research question, the available resources; the study design (e.g. cross-sectional vs longitudinal). Often,
whole body two-component information (e.g., FFM and FM) is sufficient to answer a research question. Alternatively, it might be important to define where in the body a loss in adipose tissue is occurring. Therefore, you then need to consider
if the primary outcome is whole body or regional body composition data.
Other consideration includes the intended population as measuring body composition in young children or in pregnancy presents particular technological, practical, logistical and ethical challenges.