Debra A Bemben

Metabolic effects of oral contraceptives. Implications for exercise responses of premenopausal women.

Low dose oral contraceptives (OCs) minimize the risk for cardiovascular disease. Both the dose and type of the progestin determine the type of effects on carbohydrate and fat metabolism. Androgenic effects of progestins on lipid metabolism are linked to an increased risk for coronary heart disease. OCs estrogen and progestin either have antagonistic or potentiating effects on metabolism so the net effect of an OC hinges on the balance of estrogen and progestin and on the dose and androgenic nature of the progestin. Mild hyperinsulinemia and reduced insulin sensitivity still occur in women using the newer low dose OC formulations. Physical exercises positive effects on blood lipids and lipoproteins may counteract the potentially atherogenic effects of some OCs. Women who use estrogen-progestin balanced OCs have healthier lipid profiles than those who use progestin dominant OCs. Physically active women who use OCs have a reduced aerobic power which may adversely affect exercise performance. Carbohydrate availability limits endurance performance since glycogen stores are relatively small and carbohydrate substrates are needed for fat oxidation. OC users have lower blood glucose levels and reduced carbohydrate utilization than do nonusers suggesting that prolonged exercise in women challenges glucose homeostasis. OCs may cause similar effects by subduing gluconeogenesis which reduces the release of hepatic glucose. This release harms the performance of endurance exercise. Future research should examine changes in exercise response with OCs and control for types and doses of OC formulations and factors (e.g. time of OC ingestion) to reduce variability in blood levels of the steroids at the time of testing. It should investigate the interaction between OC use and exercise training in women especially OCs effects on hormonal and metabolic responses in endurance trained women.