The normal relationship between fat and lean mass for mature (21–30 year old) physically fit men and women

Abstract

AbstractObjectiveDetermine if relative body fat (%BF) remains a biological norm in physically active, non‐obese American men and women and determine reference values for other components of body composition.MethodsParticipants (n = 174 men, 70 women) were physically fit U.S. Marine 2nd Lieutenants, in their third decade of physical maturity (age 21–30). Body composition was assessed by dual‐energy x‐ray absorptiometry (DXA) and bioelectrical impedance analysis (BIA); and body images were obtained by 3D body scans.ResultsFor men and women, respectively, %BF averaged 16.2 ± 4.1 (median 15.3), 24.3 ± 4.5 (median 23.8); fat‐free mass (FFM): 67.7 ± 7.2, 49.4 ± 5.3 kg; FFM index: 21.5 ± 1.8, 18.3 ± 1.6 kg/m2; and body mass index (BMI): 25.5 ± 1.9, 24.1 ± 2.2 kg/m2. Bone mineral content (BMC) was 5% of FFM; total body water (TBW) was 70%–72% of FFM. Physique remained similar between median and higher percentiles of %BF. Only small changes in key measures were noted across the six‐month training program.ConclusionsMean %BF of healthy active men and women in 2021 remains very similar to the 15% and 25% posited in 1980, suggesting that relative body fat has a normal fat‐lean relationship in physically mature humans. These data may bring new attention to sex‐appropriate %BF.