Purpose. The purpose of this study was to determine if participation in mandatory physical training (PT) by Reserve Officer Training Corps (ROTC) cadets would promote favorable body composition (BC) changes during the first year at university versus general population students with high and low levels of physical activity (PA). Methods. Thirty-seven (18.4 ± 0.7 years old), healthy, non-smoking, resident men, beginning their first semester at university were divided into 3 groups: Low Active (LA), HA (High Active) and ROTC cadets based on a two-mile run, and underwent measurements at baseline (beginning of freshman year) and follow-up (6 months after baseline). Measurements included BC by dual-energy x-ray absorptiometry (DXA) and circumference-based equations (CBE), 3-day food logs, physical activity assessment using the Godin Leisure-Time Exercise Questionnaire (GLTEQ), and two measures of self-efficacy. At baseline, all subjects completed fitness testing via the Army Physical Fitness Test (APFT) to predict fitness levels. Results. Percent body fat (BF) by CBE was highly correlated with percent BF (r=0.833, p<0.01), android fat (r=0.845, p<0.01), and fat mass (r=0.856, p<0.01) as measured by DXA. High Active students experienced greater losses versus LA and ROTC in percent body fat (-1.6% ± 2.5% vs. 1.9% ± 1.2% vs. 0.8% ± 2.2%, respectively) and fat mass (0.9kg ± 2.2kg vs. 2.3kg ± 1.7kg vs. 1.0kg ± 2.2kg, respectively) versus LA and ROTC students over the 6-month period. HA subjects also had significantly higher changes versus LA but not ROTC for lean mass (1.8kg ± 1.2kg vs. -0.2kg ± 2.1kg vs. 1.0kg ± 2.2kg, respectively). ROTC subjects were similar to LA students in all measures of BC change. ROTC and LA students had similar levels of activity, but significantly lower than HA subjects. No significant relationships were observed between dietary variables and self-efficacy and BC changes. Conclusions. These results suggest that PT conducted by ROTC is not sufficient to off-set gains in percent BF and fat mass, and additional PA may be required to promote favorable BC changes. Additionally, CBE are appropriate field measures of percent BF.