Density of fat-free body mass: relationship with race, age, and level of body fatness.
The two-compartment body composition method assumes that fat-free body mass (FFM) has a density of 1.100 kg/l. This study tested the hypothesis that FFM density is independent of race, age, and body fatness. Subjects were 703 black and white subjects, ages 20-94 yr, with body mass index (BMI) 17-35 kg/m2. Body composition was assessed using a four-compartment model based on tritium dilution volume, body density by underwater weighing, bone mineral by dual-energy X-ray absorptiometry, and body weight. No relationship was observed between FFM density and race or BMI. A tendency was observed for a lower FFM density only in older white women. The difference in percent body fat (delta fat) between the four-compartment model and underwater weighing was < 2% for all groups. Race, age, and BMI explained only 2.3 (women) and 1.4% (men) of the variance in delta fat, whereas the total body water fraction of FFM explained 77%. In contrast to current thinking, these results show that the assumption of constant FFM density is valid in black, elderly, and obese subjects.
Visser
M
M
Department of Human Nutrition, Wageningen Agricultural University, The Netherlands.
Gallagher
D
D
Deurenberg
P
P
Wang
J
J
Pierson
R N
RN
Heymsfield
S B
SB
D000273:Adipose Tissue / Q000033:anatomy & histology*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D044383:Black People; D001823:Body Composition; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D044465:White People