Subjects with nonalcoholic fatty liver disease (NAFLD) will complete baseline testing and then be assigned to either the high fructose corn syrup diet or the standard diet (low in high fructose corn syrup) for 4 weeks. Post intervention testing will be completed after the subjects have completed the 4 week diet intervention.

Subjects without nonalcoholic fatty liver disease (Non-NAFLD) will complete baseline testing and then be fed a high fructose corn syrup diet for 4 weeks. Post intervention testing will be completed after the subjects have completed the 4 week diet intervention.

Subjects will consume a high fructose corn syrup diet for 4 weeks. The food will be prepared by the bio-nutrition kitchen, and meals will be picked up every 3-4 days.

Determine the effect of 4-week isocaloric diet high in high fructose corn syrup (HFCS) on IHTG content measured by magnetic resonance spectroscopy (MRS).

Determine the effect of 4-week isocaloric diet high in HFCS on hepatic lipid metabolism [de novo lipogenesis, very low density lipoprotein-triglyceride (VLDL-TG) and very low density lipoprotein-Apolipoprotein B100 (VLDL-ApoB) secretion rates] by using stable isotope tracer methods.

Determine the effect of 4-week isocaloric diet high in HFCS on multi-organ insulin sensitivity by using a one stage hyperinsulinemic euglycemic clamp procedure in conjunction with muscle and adipose tissue biopsies.

Determine the effect of 4-week isocaloric diet high in HFCS on uric acid metabolism by measuring post-prandial serum uric acid concentrations and using stable isotope tracer method.