Evaluating lower limits of body fat percentage in athletes using DXA

Body fat percentage (BF%) is routinely measured in athletes to monitor training and dietary interventions. Dual energy x-ray absorptiometry (DXA) is widely considered the gold standard body composition measurement technique, but DXA BF% values measure consistently higher than other techniques. Therefore, the main purpose of this study is to determine the lowest DXA-estimated whole-body fat mass in free-living athletes with unrestricted access to food. In this cross-sectional analyses, 732 participants across 18 competitive sports (643 athletes; 88 %) plus two (male and female) "non-athlete" male and female cohorts (89 non-athletes; 12 %) underwent a whole-body DXA scan using a Horizon A Hologic™ device (software version 13.6.0.5; TBAR 1209), performed and analyzed by a single operator. The average BF % in 454 males (20.9 ± 3.8 years) was 18.2 ± 4.9 % (range 10.3 - 37.2 %), with basketball players having the lowest BF% (15.3 ± 2.6 %) and non-athletes having the highest BF% (21.6 ± 5.4 %) (1-way ANOVA between 10 teams: F = 12.3; p < 0.0001). The average BF% in 278 females (21.3 ± 5.5 years) was 27.1 ± 5.1 % (range 16.2 - 45.3 %), with runners having the lowest BF% (23.5 ± 3.5 %) and non-athletes having the highest BF% (31.7 ± 6.3 %) (1-way ANOVA between 10 teams F = 12.9; p < 0.0001). In absolute values (kg), the average body fat for males was 19.9 ± 8.0 kg (range 6.7 - 62.0 kg) and 18.9 ± 6.4 kg (range 9.2 - 49.7 kg) for females. These data suggest that the lower limits of whole-body fat mass in free-living competitive athletes is approximately 10 % for males and 16 % for females. Whether these DXA-derived fat thresholds represent "healthy" levels, or how much of these DXA-derived fat depots represent essential fat stores located within lean soft tissue mass, remains unclear.