Inclusion Criteria:

• Age 18-40 years (inclusive)
• Body mass index greater than or equal to 25 kg/m2 and less than 30 kg/m2
• Weight stable (no change in body mass greater than 5 Lbs. within the previous 6 months.
• Willing to abstain from caffeine and alcohol for 24-hours prior to two different study visits
• Competency in English as assessed by comprehension of the Informed Consent. This is study involves invasive procedures and infusion of a systemic vasoactive agent (isoproterenol); for safety reasons, the ability for clear and rapid communication will be necessary between the research participants and the investigators.

Exclusion Criteria:

• History of autonomic, cardio-pulmonary, and/or metabolic disease (including heart failure, hypertension, arrhythmia, vascular disease, and/or diabetes)
• Pregnancy or breast feeding
• Habitual use of tobacco/nicotine products or recreational drugs (2 or more uses within the previous month)
• History of a "sulfite allergy" as it is a relative contraindication to isoproteronol use.
• Has ingested vitamin supplements and/or antioxidant supplements during the previous 4-weeks (e.g. Vitamin C, Vitamin E, Multi-vitamins, etc.)