Individuals submitted to a high-fat or a high-fructose/sucrose diet develop, over a 6 day-period, several features of the metabolic syndrome, including increased plasma triglycerides, increased intrahepatic lipids, and decreased hepatic insulin sensitivity. It has been recently observed that the increase in intrahepatic lipids observed after a high fat diet is largely prevented when protein intake is concomitantly increased. This suggests that dietary protein protects the liver against some of the deleterious effects of a high fat diet. Mechanisms underlying this effect of protein may include an increased hepatic fat oxidation.