How Low Can You Go - Minimum Body Fat In 732 Athletes/non-athletes Using Dxa Scans

Body composition, particularly body fat percentage (BF%), is used to evaluate training and diet in sport. Dual energy x-ray absorptiometry (DXA) scans are fast becoming the gold standard measurement technique (3-compartment model) but measures higher BF% values compared with other (2-compartment) techniques. PURPOSE: To 1) evaluate the linearity and lower limit thresholds for BF% using a DXA scan and 2) assess relationships between lean, fat, and bone mass in a cohort of college-aged athletes (88%) and non-athletes (12%). METHODS: In this cross-sectional analyses, 732 different participants across 18 competitive sports (643 athletes; 88%) and two non-sports teams (89 non-athletes; 12%) underwent a whole-body DXA scan using a Horizon A Hologic™ device (software version 13.6.0.5; TBAR1209 calibration). All scans were performed and analyzed by a single operator, with the feet excluded when height > 1.96 m. RESULTS: 454 males (20.9 ± 3.8 years) and 278 females (21.3 ± 5.5 years) completed whole-body scans. Average BF% was 18.2 ± 4.9% (range 10.3 - 37.2%) for males and 27.1 ± 5.1% (16.2 - 45.3%) for females. A significant negative correlation was noted between total lean mass (kg) vs. BF% when data were combined (r = -0.35;p < 0.0001; N = 732). When data were separated by sex, a significant positive correlation was seen in the male subgroup (r = 0.32;p < 0.001; N = 454), with no significant correlation seen in the female subgroup (r = 0.10; p = 0.09; N = 278); highlighting a curvilinear relationship between total lean mass vs. BF% (see Figure). Bone mineral content (BMC) was positively related to total lean mass (r = 0.87;p < 0.0001) and negatively related to BF% (r = -0.46; P < 0.0001) only when data were combined (N = 732). CONCLUSION: Using a DXA scan, the relationship between lean mass and BF% appears curvilinear, with a minimum healthy threshold (i.e., essential fat) for collegiate athletes being 10% in males and 16% in females. Bone mass is more strongly related to lean mass than BF%.