The purpose of this research study is to learn more about how our body produces sugar, breaks down fat for fuel, and makes insulin (the major hormone that controls the production of blood sugar and fat breakdown) during a 24-hour day and how body fat and muscle are involved in these processes.

The purpose of this study is to determine whether there are diurnal differences in postprandial beta-cell function and hepatic insulin sensitivity and the factors that influence these metabolic functions, including insulin signaling, adipose tissue and systemic inflammation, nicotinamide phosphoribosyltransferase (NAMPT)-mediated nicotinamide adenine dinucleotide(NAD) biosynthesis, and sirtuin (silent mating type information regulation 2 homolog 1 (SIRT1)) in overweight human subjects.

Inclusion Criteria:

• Females
• 18-55 years old
• BMI between 25.0-29.9 kg/m2
• Must be sedentary (regular exercise <1hour/week or <2 times/week

Exclusion Criteria:

• Regular exercise (>1hour/week or >2 times/week)
• Diabetes
• Severe organ dysfunction
• Smokers
• Severe hypertriglyceridemia (>300 mg/dl)
• Medications that may alter the results of the study
• Pregnant
• Breastfeeding

The study population will consist of female subjects of all races and ethnic groups. Participants will be recruited by reviewing our database of research subjects containing thousands of research study volunteers and by St. Louis metro area postings.