Maximal fat oxidation, but not aerobic capacity, is affected by oral contraceptive use in young healthy women

Synthetic ovarian hormones contained in oral contraceptives (OC) may alter the aerobic capacity and lipid metabolism in oral contraceptive users (OC+) compared with non-users (OC-). The aim of this study was thus to investigate the differences between OC- and OC+ (1) in cardiorespiratory parameters at the anaerobic threshold (AT) and at the maximal aerobic capacity and (2) in the exercise intensity (Lipox(max)) at which lipid oxidation rate is maximal (MLOR). Twenty-one healthy untrained women (22.0 +/- A 0.6 years old) who took OC (OC+; low-dose monophasic OC, n = 11) or not (OC-; n = 10) performed two experimental exercise sessions. In the first one, cardiorespiratory parameters at the AT and at the maximal aerobic capacity were assessed during a maximal incremental exercise session. In the second one, Lipox(max) and MLOR were measured during a submaximal incremental exercise session. No significant difference was observed in cardiorespiratory parameters at the AT and at the maximal aerobic capacity between OC+ and OC- women. OC+ women showed higher MLOR (7.6 +/- A 1.9 vs 4.6 +/- A 1.0 mg min(-1) kg FFM-1; p < 0.01) that was elicited by higher Lipox(max) (45.2 +/- A 5.2 vs 36.2 +/- A 4.1 % of VO2max; p < 0.001) compared to OC- women. OC+ and OC- women did not differ in cardiorespiratory parameters at the AT and at the maximal aerobic capacity. However, OC+ women show higher MLOR and Lipox(max) compared with OC- women. The hormonal status appears to be an important MLOR and Lipox(max) determinant in untrained women.