Effects of a life long high-fat/high sugar diet (Western diet: WD) upon pyruvate liver metabolism were observed in a group of young adult male guinea pigs (N=26). Proton density fat-fraction images were reconstructed using IDEAL water fat separation. Metabolism data were obtained using dynamic spectroscopy of hyperpolarized carbon-13 enriched pyruvate. Guinea pigs fed a life long WD displayed a significantly higher hepatic fat fraction and a delayed time to peak for the conversion of pyruvate to lactate. These results indicate that life long consumption of a WD in growing animals is associated with markers of dysfunctional hepatic metabolic function.