Abstract: The present application relates to methods of lowering at least one of blood glucose, liver fat, liver glycogen, insulin or insulin resistance in a mammal, for example, mammals who are obese, or have metabolic disease, fatty liver disease, pre-diabetes or type 2 diabetes. In an embodiment, a method comprises administering to a mammal a polymer comprising L-lactate monomer, or a functionally equivalent derivative or fragment thereof, which inhibits or at least reduces D-lactate transport across the intestinal barrier. Compositions useful in the methods are also provided.