During a single 2-day, 1-night study visit, investigators will use innovative, non-invasive magnetic resonance imaging-based methods of estimating skeletal muscle oxidative phosphorylation capacity, including post-exercise chemical exchange saturation transfer (CrCEST) recovery and 31-Phosphorus (31P) magnetic resonance spectroscopy (MRS) and muscle lipid content, including 1H magnetic resonance spectroscopy (MRS) and 3-point Dixon techniques, in conjunction with a tracer-enhanced oral glucose tolerance test (OGTT*) to measure overall insulin sensitivity and the selective effect of insulin on glucose disposal (Rd). The percentage suppression of endogenous glucose production by the oral glucose load (% suppression of Ra of endogenous glucose) will also be assessed. Infusion of a glycerol tracer permits assessment of lipolysis in both the fasting state, and also after the oral glucose load, such that the percentage suppression of lipolysis by the oral glucose load can also be calculated (% suppression of Ra of glycerol). In addition, the insulin and c-peptide minimal models will also be used to model pancreatic β-cell responsiveness to the oral glucose load and hepatic insulin extraction.