Hepatic fat accumulation is associated with diabetes and hepatocellular carcinoma (HCC). Here we characterize the metabolic response that high fat availability elicits in livers prior to disease development. After a short term on a high fat diet, otherwise healthy mice showed elevated hepatic glucose uptake and increased glucose contribution to serine and pyruvate carboxylase activity compared to control diet mice. This glucose phenotype occurred independently from transcriptional or proteomic programming, which identifies increased peroxisomal and lipid metabolism pathways. High fat diet-fed mice exhibited increased lactate production when challenged with glucose. Consistently, administration of an oral glucose bolus to healthy individuals revealed a correlation between waist circumference and lactate secretion in a human cohort. In vitro, palmitate exposure stimulated production of reactive oxygen species and subsequent glucose uptake and lactate secretion in hepatocytes and liver cancer cells. Furthermore, high fat diet enhanced the formation of HCC compared to control diet in mice exposed to a hepatic carcinogen. Regardless of the dietary background, all murine tumors showed similar alterations in glucose metabolism to those identified in fat exposed non-transformed mouse livers; however, particular lipid species were elevated in high fat diet tumor and non-tumor-bearing high fat diet liver tissue. These findings suggest that fat can induce glucose-mediated metabolic changes in non-transformed liver cells similar to those found in HCC.