Higher Usual Energy Intake, Body Mass, Body Mass Index, and Fat Free Mass Index Are Associated with Lower Attrition from an Arduous Military Selection Course (P23-005-19)

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Abstract Objectives To determine whether usual energy intake and body composition are associated with attrition from an arduous military selection course characterized by energy deficit and strenuous physical events, including fitness tests, loaded road marches, runs, land navigation, and an obstacle course. Methods Energy intake and body composition were assessed in U.S. Army Soldiers (n = 776) at the start of a military assessment and selection course. Usual energy intake (kcal) over the previous year was estimated from a 127-item Block food frequency questionnaire. Body composition measures, including body mass (kg), body mass index (BMI, body mass in kg/height in m2), fat free mass index (FFMI, fat free mass in kg/height in m2), and fat mass index (FMI, fat mass in kg/height in m2) were assessed by calibrated scale and 3-site skinfold caliper measures. Associations between energy intake, body composition, and demographics were determined with analysis of variance. Logistic regression was used to determine likelihood of attrition [odds ratio (OR), 95% confidence interval (CI)] based on quartiles of energy intake and body composition. Models were adjusted for age, education, duration of aerobic exercise, duration of strength training, smoking status, and smokeless tobacco use. Results Soldiers that were younger (18–24 y), engaged in longer duration of aerobic exercise (≥200 min/wk) and strength training (≥400 min/wk), had more education (≥some college), and were smokeless tobacco users had higher energy intakes (P < 0.05). Higher energy intake was associated with higher body mass and FFMI (P < 0.05). After adjustment, Soldiers with higher energy intake, body mass, BMI, and FFMI were less likely to fail the strenuous course (Q1 vs. Q2, Q3, and Q4: OR range = 0.25–0.54; 95% CI lower bound range = 0.15–0.33; 95% CI upper bound range = 0.46–0.87). FMI was not associated with attrition. Conclusions Optimization of body composition by adequate consumption of calories prior to a physically demanding military selection course may be associated with reduced attrition. Funding Sources Supported by U.S. Army Medical Research and Materiel Command. The opinions or assertions contained herein are the private views of the authors and are not to be construed as official or reflecting the views of the Army or the Department of Defense. Supporting Tables, Images and/or Graphs