Data from human and animal models strongly suggests that reduced tissue mitochondrial function can be an early marker for detection of dysfunctional metabolism. It is unclear if tissue mitochondrial dysfunction can be detected using less invasive methodology. In this project, the investigators plan to study mitochondrial bioenergetics in circulating cells and paired muscle biopsies in two metabolic disparate groups of women; healthy lean vs. obese insulin resistant women of similar age. Women of similar age that are either healthy lean or insulin resistant and obese will be recruited to participate in one study that includes a blood draw and a muscle biopsy. Mitochondrial function in circulating blood cells and muscle tissue will be determined.