Background: This study aimed to evaluate the effects of compact food bar (CFB) designed on cardiopulmonary function in men athletes who serve in military service. Materials and Methods: In this randomized, single-blind, controlled clinical trial, 46 men of military staff were arranged into 2 groups and studied for 28 days; one branch used 3 packs daily, 700 kcal each, of CFB with Functional compounds (Caffeine and L-arginine) and the other group used regular food during training course. Maximal oxygen uptake (VO₂ Max) in vitro with cardiopulmonary exercise test, body composition, and physical activity were assessed and recorded at baseline and end of the study period. Results: VO₂ Max (P = 0.05) significantly increased in CFB group compared with baseline. Moreover, VO₂ Max (P = 0.01), VO₂/HR (P = 0.04), oxygen uptake/heart rate (VO₂/HR) (P = 0.03), and ventilation per minute/oxygen uptake (VE/VO₂) (P = 0.03) significantly increased in CFB group compared with control group. In comparison, there was no significant difference in mean ventilation per minute/carbon dioxide production (VE/VCO₂) (P = 0.41), ventilation per minute (VE) (P = 0.69), and breathing frequency (P = 0.056). No significant effect of CFB was found on weight, body mass index (P = 0.23), lean body mass (P = 0.91), and body fat mass (P = 0.91). Conclusion: Our results show that intervention with CFB is more effective than regular diet in improving cardiopulmonary function in men athletes who serve in military service.