The purpose of this study was to examine how the maximal fat oxidation rate is affected in two groups of women with different fat mass percentages. Thirty-four women with sedentary behavior (aged 18–25 years) were divided into 2 groups according to their body fat percentage. (<32% of body fat was considered as a threshold following American College Sport Medicine [ACSM] indications). Body fat percentages were assessed by anthropometry, then subjects performed an adapted graded exercise test on a treadmill to determine maximal oxygen consumption and fat oxidation rates during exercise. There were significant differences (p<0.05) in maximal cardiorespiratory capacity (34.4±4.4 vs 30.4±10.4 mL x kg-1 x min-1) and maximal fat oxidation rates (0.39±0.05 vs 0.31±0.06 g x min-1) between the lower risk group when compared to the higher risk group. There was no correlation between body fat percentage (BF%) and fat oxidation rates in both groups. In conclusion, cardiorespiratory capacity and substrate oxidation are different when two groups of women divided by ACSM recommendations are considered and these results could help clinicians and trainers to prevent weight gain and/or promote body fat and body weight loss.