Although hormonal responses to exercise performed in fed state are well documented, far less in known about the effect of a single exercise bout, performed after overnight fasting, on cardio-respiratory responses and hormones secretion. It has been reported that recently discovered hormones as leptin and ghrelin may affect cardiovascular responses at rest. However, their effect on the cardiovascular responses to exercise is unknown. This study was designed to determine the effect of overnight fasting on cardio-respiratory responses during moderate incremental exercise. We have hypothesised that fasting/exercise induced changes in plasma leptin/ghrelin concentrations may influence cardiovascular response. Eight healthy non-smoking men (means±SE.: age 23.0±0.5 years; body mass 71.9±1.5 kg; height 179.1±0.8 cm; BMI 22.42±0.49 kg. m-2 with VO2max of 3.71±0.10 l. min-1) volunteered for this study. The subjects performed twice an incremental exercise test, with the increase of power output by 30 W every 3 minutes. Tests were performed in a random order: once in the feed state-cycling until exhaustion and second, about one week later, after overnight fasting-cycling until reaching 150 W. In the present study we have compared the results obtained during incremental exercise performed only up to 150 W (59±2% of VO2max) both in fed and fasted state. Heart rate measured during exercise at each power output, performed in fasted state was by about 10 bt. min-1 (p= 0.02) lower then in fed subjects. Respiratory quotient and plasma lactate concentration in fasted state were also significantly (p< 0.001) lower than in the fed state. Pre-exercise plasma leptin and ghrelin concentrations were not significantly different in fed and fasted state. Exercise induced increase in hGH was not accompanied by a significant changes in the studied gut hormones such as ghrelin, leptin, and insulin, except for plasma gastrin concentration, which was significantly (p= 0.008) lower in fasting subjects at the power output of 150 W. Plasma [IL-6] at rest before exercise performed in fasted state was significantly (p= 0.03) elevated in relation to the fed state.