Abstract Background Fasting prior to anesthesia is considered aspiration prophylaxis. However, prolonged food and drink restrictions may increase the risk of other complications. The aim of this study was to assess whether a carbohydrate-enriched drink (Nutricia™ preOp®), recommended by the enhanced recovery after surgery (ERAS) protocol, can improve body hydration in fasting healthy individuals. Methods Measurements were done with the bioelectric impedance analysis with a Fresenius body composition monitor. Body composition, total body water, water distribution, and hemodynamic parameters were measured at the beginning of the study and after 10 h and 12 h of fasting. Patients fasted for 10 h and then were divided into two groups: the control (n = 40) and the pre-op group (n = 41). The pre-op group received 400 mL of Nutricia™ preOp®, as suggested in the ERAS guidance. The two-tailed Student’s t test was used to compare two groups with normally distributed data and homogenous variances; if variances were heterogeneous, Welch’s test was used. The Mann-Whitney U test was used to compare two groups with non-normal data distribution. p