Impact of Exercise on the Metabolic Consequences of Overeating (XO)

If subjects are eligible and decide to participate, they will take part in two identical study trials. One is scheduled before and the other is scheduled after 1 week of overeating controlled by the study team. Subjects who exercise regularly will be instructed to exercise the day before their first study trial - and they will be required to exercise during 6 of the 7 days of the overeating period (including the day before their second study trial). Subjects who do not regularly exercise (no planned physical activity) will remain inactive until the completion of both study trials.

Before each study trial If a subject is a regular exerciser, they will be asked to come to the Substrate Metabolism Laboratory in the afternoon before each of the 2 study trials to exercise in the lab for 45 min at a moderate intensity. The evening before the study trial, all subjects will need to eat a standardized dinner meal and snack. They must eat the meal and snack at specific times as indicated by the research staff. After eating the snack, subjects will need to fast (no food or beverages - besides water) overnight.

During each study trial Subjects will arrive at the Substrate Metabolism Laboratory at 7:00AM and will rest quietly for approximately 30 min. After which, the study team will measure their resting blood pressure and their resting metabolic rate. An intravenous catheter (IV) will then be placed in a vein of the subject's hand or forearm for blood sampling. The research team will then collect a small sample of fat tissue in the subject's abdomen with a needle. Next, subjects will drink a sweet sugar solution for an Oral Glucose Tolerance Test (OGTT) and the research team will collect blood samples every 15 min for 3 hours. After this 3 hour test, the IV catheter will be removed and subjects will be provided breakfast and discharged.