The aim of this study was to determine and evaluate resting energy expenditure (REE) and the utilization of nutritional substrates in 14 polytrauma patients in the ICU. Was also assessed level of impact Overhydration (OH) on the accuracy of the determination. Diagnostic investigations using indirect calorimetry (IC) was performed in 9 men and 5 women (age 30 ± 15 years, BMI 27.5 ± 9.4 kg·m-2) with polytrauma (ISS 41 ± 16). For more accurate sizing of REE and extent of utilization of nutritional substrates were used equations derived from the equation of Weir, not Softwear calorimeter. Using IC volumes were determined only inspired an expired oxygen and carbon dioxide. To determine the rate of OH was used bioimpedance analysis methods using BCM. Almost 86% (8 men and 4 women) examined patients showed hypermetabolism. Average REE value was 2241.38 ± 854.27 kcal·day-1, which represented an average increase of prediction of 38.09 ± 49.09% due to the physiological condition. A statistically significant relationship was demonstrated between REE determined using the Weir equation according and the Harris-Bennedict equation without (P = 0,01) with deduction of OH (P = 0,007) only in men. In clinical practice, significant correlations were established between the REE-IC and BSA (P < 0,01), LTM (P < 0,05),...