The Effect of Lactation on Insulin Sensitivity and Lipolysis in Women

Inclusion Criteria: * A history of GDM (as defined as the American Diabetes Association criteria) * Delivered a singleton, live birth at ≥ 35 weeks gestation within the past 18 months * HbA1C \< 6.5% at time of screening * Delivery within the past 18 months * Breast Feed Group: exclusively or mostly breast-fed (\< 6 ounces of formula/24 hours at 6-9 weeks of delivery) for at least 4-6 months Exclusion Criteria: * Currently lactating or lactation within the past 1 month at the time of the screening visit * Diagnosis of diabetes (T1D or T2D) prior to pregnancy * Current use of any glucose-lowering agents * Pregnancy related medical problems including preeclampsia * Major congenital fetal anomalies * Creatinine \> 1.5mg/dL, Hematocrit \< 35%, ALT and AST \> 2.5X upper limit of normal * Known psychiatric disorders, alcohol abuse, HIV, hepatitis, renal disease, hepatic disease, untreated heart disease, untreated thyroid disease, active systemic infection or malignancy * Illicit drug use (by the participant's self-report) * History of post-partum depression * Use of weight loss supplements or dieting 6 months prior to study * Corticosteroid or opiate use within 6 months of study