Exercise per se masks oral contraceptive-induced postprandial lipid mobilization

Because of their hormonal content, oral contraceptives may alter lipolytic activity under resting or exercise conditions in women. The aim of the present study was to compare lipid mobilization in a postprandial state at rest and during exercise in oral contraceptive users (OC+) versus nonusers (OC-). The metabolic (glucose, glycerol, free fatty acids) and hormonal (insulin, atrial natriuretic peptide (ANP), growth hormone, insulin-like growth factor-1 (IGF-1), and catecholamines) concentrations were determined in 11 OC+ (monophasic low-dose oral contraceptives) and 10 OC- during a resting and an exercise session (45 min at 65% maximal oxygen consumption). Results were expressed as plasma concentrations and area under the concentration versus time curve values. ANP concentrations were higher in OC+ compared with OC- women at baseline (p = 0.04). Plasma concentrations of glycerol (p = 0.04), free fatty acids (p = 0.04), ANP (p = 0.02), and noradrenaline (p = 0.04) were higher in OC+ compared with OC- when both sessions were pooled. The plasma growth hormone, IGF-1, and adrenaline concentrations were not significantly different between the 2 groups. When the effect of exercise was isolated to overcome food intake and daytime variations (exercise per se using the area under the curve), no difference was observed between groups for all metabolic and hormonal variables. Overall, oral contraceptives increased lipid mobilization in the postprandial state, but this effect was blunted when lipolytic activity was stimulated by exercise per se. Oral contraceptive-induced greater lipolytic mobilization could be partly explained by greater ANP levels in OC users.