Higher Fat Ration Formulations Minimize Energy Deficit During a Short Field Training Exercise

Abstract Introduction During short-duration (<7 days) military training and operations, personnel often experience energy deficits (energy intake < energy expenditure) because of high daily energy expenditures and logistical constraints that limit food availability. One potential approach to maximize energy intake while minimizing the weight of carried provisions is to increase the fat content of rations. Accordingly, the Close Combat Assault Ration (CCAR) has been developed as a higher fat, lower volume alternative to current short-duration U.S. Military ration, the First Strike Ration (FSR). However, the impact of consuming the CCAR, compared to the FSR is unclear. Materials and Methods This study determined the effects of consuming the CCAR, compared to the FSR, during a 5-day field training exercise (FTX) on energy intake, energy balance, and physical performance. Active duty service members participating in this parallel, single-blinded trial were randomized to consume either one CCAR (n = 29; 2,851 ± 62 kcal, 86 ± 4 g protein, 332 ± 9 g carbohydrate, 127 ± 4 g fat) or one FSR (n = 28; 2,914 ± 185 kcal, 89 ± 9 g protein, 430 ± 27g carbohydrate, 97 ± 13 g fat) daily during the FTX. Energy expenditure was measured by doubly-labeled water and energy intake was calculated by measuring consumption of provided rations. To assess physical performance, participants completed a maximum vertical jump, 300-yard shuttle sprint, and lower-body strength pull before and after the FTX. Results Energy expenditure was similar (P = .68) between CCAR (3,245 ± 238 kcal·day−1) and FSR (3,276 ± 317 kcal·day−1). Energy intake was higher (P = .001) in CCAR (2,194 ± 539 kcal·day−1) compared to FSR (1,914 ± 611 kcal·day−1) resulting in lower (P = .003) overall energy deficits during the training event in CCAR (32% ± 12%) versus FSR (42% ± 11%). Lower-body power, shuttle sprint time, and peak pull force were not different between groups (P ≥ .05). Self-reported reasons for underconsumption were similar across groups (P ≥ .05), with the most commonly cited factors being not liking the food, lack of time, and lack of appetite. Conclusions These data demonstrate that higher-fat rations, such as the CCAR, may be effective as a short-term nutritional strategy to attenuate energy deficits without affecting physical performance when lower weight and volume rations are required. However, persistent energy deficits were influenced by potentially modifiable factors such as ration acceptability and time constraints, highlighting the need for continued innovation in ration design and feeding strategies to optimize energy intake during military training. Clinical Trial Registration Identifier: NCT06261437.