After the IV placement, the study team will begin a tracer-labeled glucose, or "sugar," infusion. The study team will then remove a small sample of muscle from the subjects thigh. This muscle biopsy procedure involves numbing a nickel-sized portion of the skin of the thigh with a local anesthetic, making a small incision (1/4 inch), and removing a small piece of muscle (approximately the size of 2-3 grains of rice). The incision will then be closed with a piece of sterile tape. The study team will also obtain a small sample of fat tissue from the area just underneath the skin near the belly button. This procedure involves numbing a small region of skin near the belly button with a local anesthetic, using a needle a small amount of fat tissue is removed from underneath the skin. During the procedure subjects will feel some pinching and pulling, but it should not be very painful. The injury resulting from the muscle and fat tissue biopsies is rather minor. Subjects will likely have some bruising and mild soreness, but it should not prevent them from performing their general daily activities.