Similar rates of fat oxidation during graded submaximal exercise in women of different body composition

Background. Despite the specific challenges pregnancy, menopause and contraception imposes on women’s cardiovascular health, no study has currently evaluated substrate oxidation of women differing in body composition at various exercise intensities recommended for weight loss.Methods. A total of 35 healthy women (age 30.8±9.5 yr) classified according to their BMI in normal weight (NOR; ≤24.9 kg·m²), overweight (OVW; 25-29.9 kg·m²) and obese groups (OBE; ≥30 kg·m²) completed a submaximal graded test (intensities eliciting ~30%, 40%, 50% and 60% of maximum oxygen uptake). Blood lactate, perceived exertion and absolute and relative substrate oxidation for fat (OX_FAT) and carbohydrates (OX_CHO) were measured at each stage.Results. Perceived exertion and blood lactate increased as a function of exercise but did not differ across groups. There were no significant changes in absolute and relative OX_FAT across groups, or as a function of exercise intensity. Peak OX_FAT occurred at the 40%, 50% and 40% stages for NOR, OVW and OBE groups, respectively, with no significant differences across groups.Discussion. We measured no differences, but considerable inter-individual variation, in fat oxidation in women of different body composition. This result is in agreement with previous research based on exercise performed at constant rate and in independent participant groups. Exercise prescription should emphasize individualizing testing responses for efficient weight management.