For the lipoprotein kinetics study subjects will receive an infusion of stable isotope enriched leucine and a bolus of stable isotope enriched glycerol in order to measure the rates of fatty acid synthesis, apolipoprotein and triglyceride turnover respectively. This in vivo stable isotope enrichment methodology has been widely established and used by investigators around the world for more than 30 years to examine the metabolism of various metabolites in humans.