Objective: Alterations in the autonomic nervous system (ANS) may cause impairment in the metabolic processes that can lead to weight gain. The purpose of this study was to determine the difference between the resting energy expenditure (REE) and the resting ANS activity in overweight/obese and normal-weight healthy subjects. Method: Group 1 consisted of 18 subjects with BMI 1 25 kg/m 2 , and 20 subjects with BMI ranging from 20 to 25 kg/m 2 formed group 2. Measurements of low-frequency (LF) and

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... high-frequency (HF) power components expressed in normalized units (LFnu, HFnu) and LF/HF ratio were assessed for analysis of heart rate variability, and simultaneously REE measurement was performed. Results: The mean LFnu (27.2% increased) and the LF/HF were higher and the mean HFnu was lower (29.9% decreased) in group 1 than in group 2 (p ! 0.01). Although a statistical difference was observed in REE between groups, REE per kilogram corrected for fat-free mass (REE FFMcorr ) was 21.47 8 2.92 kcal/day/kg in group 1, and 21.56 8 1.90 kcal/day/kg in group 2, and this difference was not statistically significant (p 1 0.05). Conclusion: We concluded that REE FFMcorr in overweight/ obese and normal-weight subjects were similar despite elevated sympathovagal balance in overweight/obese individuals, and REE FFMcorr should be used to avoid misestimating the REE in obese and normal-weight subjects.