Subjects will remain fasting and resting in CREU for the entire period of the study to eliminate variability in CO2 production. Breath samples in quadruplicates will be collected at 20,40,60,80,100,120,140,160,180, 200, 220 and 240 min after oral administration of glucose. During the study visit, the rate of carbon dioxide production (VCO2) will be measured for 20 minutes, two hours (120 minutes) after the oral glucose dose using an indirect calorimeter (Vmax Encore, Viasys Healthcare Inc. Yorba Linda, CA). Assessment of body composition will be performed using the Bioelectrical Impedance Analysis (BIA-Quantum IV, RJL Systems, MI). BIA calculated resistance, reactance and impedance by applying electrodes would be placed at the right wrist and ankle. Three readings for resistance, reactance and impedance will be taken for each subject then the mean of these readings will be used to determined fat free mass (FFM) and fat mass (FM). FFM and FM will be calculated using the manufacturer's software system (RJL Systems, Body Composition Analysis V.2.1). Finger-prick blood glucose samples will be assessed at the beginning and hourly until the end of the study day using glucometer (One Touch® Ultra®, LifeScan, Inc).