The effect of obesity and low-dose oral contraceptives on carbohydrate and lipid metabolism.

BACKGROUND: Combination oral contraceptives (OCs) have little effect on carbohydrate and lipid metabolism in normal-weight women. Based on lack of change in intermediate markers, as well as results of epidemiologic studies, low-dose OCs do not increase the risk of diabetes or cardiovascular disease. Obesity is a risk factor for impaired glucose tolerance, diabetes and coronary artery disease, and most previous OC studies excluded these women; thus, we have limited information about carbohydrate and lipid metabolism in obese OC users.

STUDY DESIGN: This study compared changes in carbohydrate and lipid parameters in 71 normal-weight and 38 obese women initiating the OC. Women were randomized to two pills: 30 mcg ethinyl estradiol (EE)/150 mcg levonorgestrel (LNG) or 20 mcg EE/100 mcg LNG. Participants underwent baseline and cycle-3 measurements of fasting serum glucose; insulin; triglycerides and total, low-density lipoprotein (LDL) and high-density lipoprotein (HDL) cholesterol.

RESULTS: Normal-weight and obese participants experienced similar changes in mean glucose, insulin and log homeostatic model assessment, as well as similar changes in total cholesterol, HDL and triglycerides; however, change in mean LDL (-4.9±20.6 mg/dL vs. +3.8±17.3 mg/dL) was different between the obese and normal-weight groups, respectively. Among the obese participants, change in glucose was marginally greater with the higher dose pill (p=.06); otherwise, changes between the body mass index groups were not modified by pill dose.

CONCLUSIONS: Obesity had little effect on any OC-induced changes in carbohydrate or lipid metabolism except for a borderline adverse interaction between obesity and OC dose with respect to fasting glucose and a positive interaction between obesity and OC use with respect to LDL cholesterol.