It is well-established that ingestion of a high carbohydrate as compared to high fat diet stimulates de novo lipogenesis in humans. Meta-analyses comparing isocaloric high fat and high carbohydrate diets have shown that high carbohydrate but not high fat diets increase increase serum triglycerides and lower HDL cholesterol. Since hypertriglyceridemia results from overproduction of VLDL from the liver, these data suggest the composition of the diet influences hepatic lipid metabolism. Whether this is because overfeeding fat leads to preferential deposition of fat in adipose tissue while high carbohydrate diets induce a relative greater increase in liver fat is unknown. There are no previous studies comparing effects of chronic overfeeding of fat as compared to carbohydrate on liver fat or and the sources of intrahepatic fatty acids.