Section

Assessing Adiposity

Summary of Methods Table

Table 1: Summary of methods to measure body composition from infancy through adolescence

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Assessing Adiposity – Dual Energy X-Ray Absorptiometry (DXA)

Assessing Adiposity – Methods Not Feasible in Population-level Research

Method	Age/weight limits	Indicators of weight status and excess adiposity/Estimate(s) of Body Fat	National Reference Data for U.S. Population of Children	Advantages	Disadvantages
Anthropometry Stature/ Recumbent Length and Weight	All ages	Weight for length Body Mass Index	YES (birth and older)	Simple and quick measurements Noninvasive and safe measurements Highly acceptable to participants Inexpensive and portable equipment Minimal staff training	Does not measure body fat Provides only an indicator of weight and obesity status
Anthropometry Skinfold Thicknesses	All ages	Site specific and sum of skinfold thicknesses Total body fat predicted by regression equations	YES (ages 2 months and older)	Relatively simple and quick measurements Noninvasive and safe measurements Acceptable to participants Inexpensive and portable equipment	Greater staff training and skill required Greater privacy needed to conduct measurements Requires greater child compliance; movement may cause inaccuracies particularly in younger children Measures only subcutaneous fat at various body locations Requires age- and sex-specific predictive equations that may not always be available for the study population of interest
Anthropometry Waist Circumference	Recommended for ages 8 years and older	Abdominal girth Surrogate for abdominal visceral fat /central fat distribution	YES (ages 8 years and older)	Relatively simple and quick measurements Noninvasive and safe measurements Moderate to high acceptability to participants Relatively inexpensive and portable equipment	Greater staff training and skill required Greater privacy needed to conduct measurements Greater source of embarrassment for children during measurement Includes both abdominal visceral and subcutaneous adipose tissue Difficult to find and measure anatomic location of waist consistently over time and on participants with obesity.
Bioelectrical Impedance Analysis (BIA)	All ages	Measures the impedance or resistance to the flow of an electrical current through the body to estimate TBW Total FM and total FFM predicted by regression equations	NO	Relatively simple and quick measurements Noninvasive and safe measurements Moderately acceptable to participants Inexpensive and portable equipment	Requires participant preparation such as fasting and no exercise in advance that may make it less feasible to conduct with children Requires greater compliance; movement may cause inaccuracies particularly in younger children Effects of growth and development on the limb and trunk in children violates key assumptions in using BIA to estimate fat mass unless age-, sex- and race/ethnicity-specific predictive equations are incorporated into the device being used.
Air Displacement Plethysmography (ADP)	Birth to 6 months (up to 8 kg) using PEA POD 6 years and older (35 kg to 200 kg) using BOD POD 2-5 years old using Adapter Insert made for BOD POD	Measures body volume used to estimate body density Total FM and Total FFM predicted by regression equations	NO	Relatively short duration to conduct test Noninvasive and safe measurements Moderate to high acceptability to participants	Greater staff training and skill required Greater privacy needed to conduct measurements Greater source of embarrassment for children during measurement due to need for tight-fitting clothing Equipment is expensive and not portable; only one manufacturer of equipment; generally found in specialized research centers or hospitals Requires participant preparation such as fasting in advance that may make is less feasible to conduct with children Requires greater compliance; movement may cause inaccuracies particularly in younger children
Dual Energy X-Ray Absorptiometry (DXA)	All ages (some instruments have an upper weight limit)	Instrument-specific software algorithms are used to calculate the various values for bone mineral content, “bone-free” lean mass or FFM, and FM	YES (ages 8 years and older)	Relatively short duration to conduct test Noninvasive and safe measurements Moderate acceptability to participants	Requires skilled and certified technicians to conduct test or physicians Greater privacy needed to conduct measurements Equipment is most expensive and not portable; generally found in specialized research centers or hospitals Requires greater compliance and movement may cause inaccuracies particularly in younger children; young children must be restrained Low dose ionizing radiation exposure (less than single day’s exposure from natural sources at sea level) Requires manufacturer/instrument specific algorithms that may not be available for the population of interest

Method

Age/weight limits

Indicators of weight status and excess adiposity/Estimate(s) of Body Fat

National Reference Data for U.S. Population of Children

Advantages

Disadvantages

Anthropometry
Stature/ Recumbent Length and Weight

All ages

Weight for length
Body Mass Index

YES (birth and older)

Simple and quick measurements
Noninvasive and safe measurements
Highly acceptable to participants
Inexpensive and portable equipment
Minimal staff training

Does not measure body fat
Provides only an indicator of weight and obesity status

Anthropometry
Skinfold Thicknesses

All ages

Site specific and sum of skinfold thicknesses
Total body fat predicted by regression equations

YES (ages 2 months and older)

Relatively simple and quick measurements
Noninvasive and safe measurements
Acceptable to participants
Inexpensive and portable equipment

Greater staff training and skill required
Greater privacy needed to conduct measurements
Requires greater child compliance; movement may cause inaccuracies particularly in younger children
Measures only subcutaneous fat at various body locations
Requires age- and sex-specific predictive equations that may not always be available for the study population of interest

Anthropometry
Waist Circumference

Recommended for ages 8 years and older

Abdominal girth
Surrogate for abdominal visceral fat /central fat distribution

YES (ages 8 years and older)

Relatively simple and quick measurements
Noninvasive and safe measurements
Moderate to high acceptability to participants
Relatively inexpensive and portable equipment

Greater staff training and skill required
Greater privacy needed to conduct measurements
Greater source of embarrassment for children during measurement
Includes both abdominal visceral and subcutaneous adipose tissue
Difficult to find and measure anatomic location of waist consistently over time and on participants with obesity.

Bioelectrical Impedance Analysis (BIA)

All ages

Measures the impedance or resistance to the flow of an electrical current through the body to estimate TBW
Total FM and total FFM predicted by regression equations

Relatively simple and quick measurements
Noninvasive and safe measurements
Moderately acceptable to participants
Inexpensive and portable equipment

Requires participant preparation such as fasting and no exercise in advance that may make it less feasible to conduct with children
Requires greater compliance; movement may cause inaccuracies particularly in younger children
Effects of growth and development on the limb and trunk in children violates key assumptions in using BIA to estimate fat mass unless age-, sex- and race/ethnicity-specific predictive equations are incorporated into the device being used.

Air Displacement Plethysmography (ADP)

Birth to 6 months (up to 8 kg) using PEA POD
6 years and older (35 kg to 200 kg) using BOD POD
2-5 years old using Adapter Insert made for BOD POD

Measures body volume used to estimate body density
Total FM and Total FFM predicted by regression equations

Relatively short duration to conduct test
Noninvasive and safe measurements
Moderate to high acceptability to participants

Greater staff training and skill required
Greater privacy needed to conduct measurements
Greater source of embarrassment for children during measurement due to need for tight-fitting clothing
Equipment is expensive and not portable; only one manufacturer of equipment; generally found in specialized research centers or hospitals
Requires participant preparation such as fasting in advance that may make is less feasible to conduct with children
Requires greater compliance; movement may cause inaccuracies particularly in younger children

Dual Energy X-Ray Absorptiometry (DXA)

All ages (some instruments have an upper weight limit)

Instrument-specific software algorithms are used to calculate the various values for bone mineral content, “bone-free” lean mass or FFM, and FM

YES (ages 8 years and older)

Relatively short duration to conduct test
Noninvasive and safe measurements
Moderate acceptability to participants

Requires skilled and certified technicians to conduct test or physicians
Greater privacy needed to conduct measurements
Equipment is most expensive and not portable; generally found in specialized research centers or hospitals
Requires greater compliance and movement may cause inaccuracies particularly in younger children; young children must be restrained
Low dose ionizing radiation exposure (less than single day’s exposure from natural sources at sea level)
Requires manufacturer/instrument specific algorithms that may not be available for the population of interest