RT Journal Article SR Electronic T1 Body composition of extreme performers in the US Marine Corps JF BMJ Military Health JO BMJ Mil Health FD British Medical Journal Publishing Group SP e002189 DO 10.1136/military-2022-002189 A1 Adam W Potter A1 L D Soto A1 K E Friedl YR 2022 UL http://militaryhealth.bmj.com/content/early/2022/11/02/military-2022-002189.abstract AB Background The creation of highly muscled and strong fighters is a recurring theme in human performance enhancement concepts. Physical readiness standards, intended to prevent obesity in the military, produce contradictory objectives, hounding large individuals to lose weight because of confusion between body size and body composition. Through selection, specialised training and policy exceptions the US Marine Corps has successfully developed a unique group of large (body mass index (BMI) >30 kg/m2) and strong individuals, the body bearers (BB) who carry coffins of Marines to their final resting place.Methods We examined the relationship between adiposity and body size from nine male BB (age 25.0±2.1, height: 1.84±0.04 (1.80–1.92) m, BMI: 33.0±2.1 (30–37) kg/m2). Body composition was assessed by dual-energy X-ray absorptiometry (DXA), bioelectrical impedance (BIA) and tape measured abdominal circumference (AC)-based equations and from three-dimensional scanning (3DS).Results Measures were made of fat-free mass (FFM): 90.5±7.0 (82.0–106.7) kg, where FFM included total body water: 62.8±5.0 (55.8–71.8) L, representing 69±2 (67–73) % of FFM, along with calculated FFM index: 26.8±2.4 (24.4–32.9) kg/m2). DXA measures were made for bone mineral content 4.1±0.4 (3.5–4.9) kg, bone mineral density (BMD) 1.56±0.10 (1.37–1.76) g/cm2 and %BF 19.5±6.6 (9.0–27.8). Additional measures of percent body fat (%BF) were made by AC: 20.3±2.9 (15.2–24.6), BIA: 23.7±6.4 (9.8–29.2) and 3DS: 25.5±4.7 (18.9–32.2). AC %BF reasonably matched DXA %BF, with expected overprediction and underprediction at low and high DXA %BF. BIA %BF was affected by deviations from assumed FFM hydration (72%–73%).Conclusion These men are classified as obese by BMI but carried massive amounts of muscle and bone on their large frames, while presenting a range of %BF irrelevant to strength performance. BMI did not predict obesity and adiposity had no association with muscle mass and strength performance.Data are available on reasonable request. The data presented in this study are available on request from the corresponding author. The data are not publicly available due to privacy and associated regulatory constraints.