Effect of exercise intensity on fat utilization in males and females

This study was conducted to assess fat utilization across different exercise intensities and between males and females. Eleven males and 11 females completed a maximal test and four submaximal trials at 40%, 50%, 60%, and 70% VO2 peak. The VO2 peak and ventilatory threshold (VT) were assessed during the maximal test. Caloric expenditure (Cal), carbohydrate (COX), and fat oxidation (FOX) were measured during each submaximal trial. Maximal fat oxidation (Fmax) was determined as the intensity where the highest FOX was observed. There was no main effect of intensity on FOX. FOX was higher in (p < 0.05) in women than in men at 40% VO2peak. The Fmax occurred most frequently at 60% VO2peak and correlated with VT (r = 0.62) and VO2 peak (r = 0.64). In conclusion, despite the fact that Fmax is most frequently observed at 60% VO2 peak, rates of fat oxidation remained statistically similar across intensities from 40% to 70% VO2peak. Women oxidized more fat than men at 40% VO2peak, but this gender difference did not occur at higher intensities. It appears that exercising within the moderate intensity domain will produce similar rates of fat utilization.