Energy Expenditure and Water Turnover Assessed by Doubly Labeled Water during Manual Work in a Dry and Warm Environment

Abstract

Objective: During training and other strenuous physical activity in the mountains, deserts, and other wilderness areas, those consuming pre-packaged rations or take-along-food often have difficulty maintaining adequate energy, water and electrolytes, and carbohydrate intakes. This study assessed the effects of ad libitum consumption of a carbohydrate beverage supplement (8% maltodextrin sweetened with aspartame) on energy and carbohydrate intakes of physically active test volunteers. Methods: Energy and carbohydrate intakes of volunteers randomly assigned to receive either a carbohydrate beverage supplement (CHO) (n=32) or a non-caloric placebo beverage (PLACEBO) (n=31) during an 11-day field training exercise were assessed. Mean total energy expenditure (TEE), water turnover (R_H2O), and total body water (TBW) were measured in a sub-group of volunteers (CHO: n=10, PLACEBO: n=9) using the stable isotopes ²H₂O and H₂¹⁸O. Results: The CHO group had greater daily energy intake (EI_CHO: 12.8±0.6 MJ/day; EI_PLACEBO: 11.0±0.8 MJ/day; p<0.05) and carbohydrate intake (CHO: 470±139 g/day; PLACEBO: 317±68 g/day; p<0.05). No differences were observed in TEE (TEE_CHO: 18.41±4.40 MJ/day; TEE_PLACEBO: 16.12±2.70 MJ/day), TBW (TBW_CHO: 46.9±5.5 L; TBW_PLACEBO: 44.5±3.3 L) or water turnover (R_H2O–CHO: 5.6±1.1 L/day; R_{H2O–PLACEBO}: 5.1±0.7 L/day) between groups. Discussion: Providing a carbohydrate beverage may reduce energy and CHO deficits that commonly occur during recreational treks or in those working for extended periods in wilderness environments.