Effect of Caffeine Intake on Fat Oxidation During and After Aerobic Exercise in Women Using Oral Contraceptives: A Randomized, Double-Blind, Crossover Trial.

Despite extensive research on the effects of caffeine intake on fat oxidation during and after aerobic exercise, its effects on women using oral contraceptives (OCs) remain unclear. This study investigated the effects of caffeine intake on fat oxidation during and after aerobic exercise in women using OCs. This study included 13 sedentary women using OCs. The subjects completed three consecutive 10-min bouts of cycling at 40% peak oxygen uptake separated by 10-min rest periods. Each session was conducted 60 min after intake of either caffeinated coffee (CAF; 5 mg/kg) or decaffeinated coffee (CON) in a randomized, double-blind, crossover design. Serum caffeine concentrations were measured before intake, preexercise, immediately postexercise, and 30, 60, and 90 min postexercise. Fat oxidation was measured before intake, preexercise, during exercise (EX1 and EX2), immediately postexercise, and 30, 60, and 90 min postexercise. The serum caffeine concentration in the CAF was significantly higher than that in the CON preexercise, immediately postexercise, and 30, 60, and 90 min postexercise (all p < .001). Fat oxidation in the CAF was significantly lower than that in the CON before intake (p < .05) but higher than that in the CON immediately postexercise (p < .05). The change in fat oxidation in the CAF was significantly higher than that in the CON at preexercise, EX1, immediately postexercise, and 30, 60, and 90 min postexercise (all p < .05). This study suggests that caffeine intake before exercise enhances fat oxidation during and after exercise in women taking OCs.