Relationships Between Sleep And Body Composition Changes In US Army Basic Combat Training

Insufficient sleep is a common challenge in the military. Rigorous training phases, such as Basic Combat Training (BCT), are often associated with changes in habitual sleep characteristics. In a recent study, trainees reported decreases in sleep quality and habitual sleep duration during BCT, with the majority (~76%) reporting <7 hours of sleep per night, which is less than the general recommendation for adults. Poor sleep characteristics are associated with higher BMI, increased body fat (BF), and decreased lean mass (LM). While previous work demonstrates that BCT favorably alters body composition, the influence of sleep characteristics on body composition changes during BCT are unknown. PURPOSE: To understand relationships between sleep characteristics and changes in body composition during BCT. METHODS: Participants were 1608 trainees (female = 553), mean age 20.83 ± 3.7 years (range 17-39). During the first (T1) and final (T2) weeks of BCT, trainees completed the Pittsburgh Sleep Quality Index, which measures sleep quality and duration, and had their body composition assessed using dual-energy X-ray absorptiometry. Linear mixed models were used to examine the relationships between sleep changes and body composition changes. RESULTS: Findings are presented in Table 1. Trainees who reported a decrease in sleep duration from T1 to T2 lost less BF than those who reported an increase or no change in sleep duration across BCT. Changes in sleep quality were not related to changes in fat mass. Neither changes in sleep duration nor quality were related to changes in lean mass. CONCLUSION: Healthy body composition is associated with improved physical performance, fewer musculoskeletal injuries, and lower all-cause discharge from military service. This analysis provides important evidence that encouraging healthy sleep habits during BCT may facilitate healthy body composition changes during training, which can positively influence overall training outcomes. - Table 1 Δ Lean Mass (kg) Δ Fat Mass (kg) β (95%CI) P β (95%CI) P Change in Sleep Duration Increase -0.021 (-0.293, 0.251) 0.88a 0.210 (-0.203, 0.624) 0.319a No Change - - - - Decrease 0.170 (-0.036, 0.376) 0.106a 0.399 (0.086, 0.712) 0.013a Change in Sleep Quality Increase -0.101 (-0.369, 0.167) 0.46b -0.168 (-0.575, 0.239) 0.418b No Change - - - - Decrease -0.139 (-0.348, 0.070) 0.192b -0.145 (-0.463, 0.172) 0.370b