Table 1.

Most commonly used total body composition methods

Method	Basis	Assumptions	Body composition measured
Whole body plethysmography (Bod Pod)11	Body volume and weight to determine density	Density of fat and lean mass is constant with age, BMI, and ethnicity	Two compartments, fat and fat free mass
DXA22	Absorption of two different energy X‐rays	X‐ray absorption is directly related to bone, fat, and lean mass	Direct measure of bone density, fat, and lean mass does not measure muscle mass
Bioelectrical impedance/bioelectrical spectroscopy16, 17	Resistance and reactance to a single or multiple frequency (BIS) electrical current	Resistance and reactance values are associated with body water content	Value is strongly associated with total body water, including intracellular and extracellular; does not measure muscle mass
24‐h urine creatinine34	Excretion of creatinine in a 24‐h urine collection	No urine is lost during collection period; no dietary creatinine; creatinine excretion reflects total body creatine pool; creatine pool size is a measurement of muscle mass	Total body creatine pool size, skeletal muscle mass
D3‐Creatine dilution37	Enrichment of D3‐creatinine in single urine sample	Urine D3‐creatinine represents muscle D3‐creatine enrichment; creatine pool size is a measurement of muscle mass	Total body creatine pool size, skeletal muscle mass