GENERAL STUDY DESIGN To avoid potential confounding hormonal effects, all women will be studied in the early follicular phase of their menstrual cycle. Subjects will be advised of what they should be eating in the 3 days leading up to their hospital visit to maintain their weight. Subjects will also complete a three day food journal before their hospital visit. The day prior to the study trial admission, subjects will need to eat pre-prepared standardized meals for breakfast, lunch, dinner and an evening snack that the study team has given them.