Table 1 Summary of assumptions underlying different techniques, their availability, and their main advantages and disadvantages.

Technique	Assumptions made	Reference data	Availability*	Advantages/disadvantages
Skinfolds – raw	Constant skin protein content	Y	+++	For: simple measure of regional fat
				Against: no information on lean mass
Skinfolds – equations	Skinfolds ∝ whole body fat	N	+++	For: simple and quick
				Against: population specific, poor accuracy in individuals and groups
Body mass index	Var weight  =  var fat	Y	+++	For: simple and quick
				Against: measures nutritional status not body composition
Waist circumference	Waist ∝ central fat	Y	+++	For: simple, quick, robust measure of abdominal fat
				Against: not so accurate as measure of internal visceral fat
Impedance	Conductivity ∝ body water	N	++	For: simple and quick
				Against: population specific; poor accuracy in individuals and groups
DXA	Constant attenuations of FFM and F	N	++	For: accurate for limb lean and fat
				Against: radiation exposure; whole body bias ∝?size, sex, fatness
Densitometry†	Constant Dffm and Df	N	+	For: acceptable two‐component technique
				Against: effects of disease on lean mass reduce accuracy
Isotope dilution	Constant Hffm	N	+	For: only technique acceptable in all age groups
				Against: delayed results; inaccurate if disease affects Hffm
MRI	Electromagnetic properties	N	+	For: accurate for regional AT
				Against: expensive, limited availability, measures AT not fat
TOBEC	Conductivity ∝ body water	N	+	For: acceptable two‐component technique
				Against: rarely available, accuracy unknown
TBK	Constant K in cell mass	N	+	For: measures functional component of body composition
				Against: rarely available, poor accuracy for fatness
Multicomponent models	Constant Dprot and Dmin,	N	+	For: most accurate approach, all measurements acceptable
	constant mineral composition			Against: expensive, specialist research approach

*Availability: +, low; ++, medium; +++, high.

†Densitometry by air displacement plethysmography (Bodpod)

AT, adipose tissue; D_f, density of fat; D_ffm, density of fat‐free mass; D_min, density of mineral; D_prot, density of protein; F, fat; FFM, fat‐free mass; H_ffm, hydration of fat‐free mass; K, potassium; Var, variability.