Body weight and body composition changes during military training and deployment involving the use of combat rations: a systematic literature review

Dismounted military personnel operate in physically and psychologically demanding environments, with energy intake from combat rations often falling short of their requirements, leading to reductions in body weight and changes in body composition, which can impact both their health and performance. This review systematically investigated the effects of the continual use of combat rations for periods of 3-40 d on body weight and/ or body composition in military personnel engaged in training or deployment. In all, ten databases were searched from their inception until October 2016. Outcome data were described narratively, with studies assessed for quality and risk of bias. A total of thirty studies undertaken over 3-34 d were included. Studies were rated positive, neutral or negative in quality according to the Academy of Nutrition and Dietetics Quality Checklist, with many at risk of bias. Reductions in mean body weight varied, from a negligible decrease of 0.1% during 8 d of combat training to a substantial decrease of approximately 8.3% during 12 d of energy restriction during a US Army Ranger course. Decreases in fat mass, fat- free mass and percentage body fat were also reported. There is thus evidence that the continual use of combat rations for periods of 3- 34 d results in reductions in body weight and body composition changes which, in some scenarios, may impact on the performance of troops. Body weight and composition should be routinely monitored before and after field activities, and at more regular intervals depending on the length, intensity and type of activity being undertaken.