Military training is conducted to develop individual and team skills in a progressive manner to prepare trainees to be able to perform their chosen job role. In undertaking these activities trainees are exposed to physically demanding tasks which will elicit physiological adaptations, intended to improve role-related fitness. However, long physically active days combined with sub-optimal nutritional intake can potentially be detrimental to health, impair performance and increase injury risk. The aim of the research presented in this thesis is to evaluate the nutritional behaviours of British Army Officer Cadets (OCs), in relation to their physical activity during military training, to inform evidenced based nutritional strategies to improve physical health and performance. The first four studies in this thesis report data collected during three different military training settings: on the academy grounds(CAMP; nine days), on field exercise (FEX; five days), and a training period that was a combination of the two (MIX; nine days). Study 1 quantified the Energy Intake (EI) and macronutrient intake of OCs during these settings. Energy intake was lower than thresholds in military nutritional guidelines and carbohydrate and protein intake were below athletic guideline thresholds. Study 2 showed that EI was lower than Energy Expenditure (EE) during training (indicating a negative Energy Balance; EB), however OCs body mass did not change over training (indicating EB). It has been suggested that body
mass maintenance during negative EB may be a consequence of reduced metabolic functions in compensation for a lack of available energy. Study 3 estimated the Energy Availability (EA) of OCs during the same training periods and demonstrated EA to be low during times of field exercise, due to high EE and low EI. Study 4 showed that during FEX the distribution of energy and macronutrient (in particular protein) intake was suboptimal, perhaps reflecting sporadic eating due to limited time to eat. A nutrition intervention was therefore explored in Study 5 to investigate if two protein-rich supplements per day (217 kcal, 23.3 g protein, 13.6 g carbohydrate and 8.2 g fat; compared to a control group - no supplement) for 8 days could mitigate physical performance decrements associated with periods of negative EB during FEX. The FEX involved prolonged load carriage activity and resulted in a 2-day period of negative energy balance and low EA. The protein-rich supplement increased protein intake above athletic guidelines. However, pre- and post-FEX physical performance did not differ,
irrespective of group. In summary, the research presented in this thesis is the first to quantify the nutritional behaviours of military personnel in relation to the physical demands across a range of military training settings which can be used to inform evidenced-based feeding interventions.