There are some indications that Chromium(III) functions as a co-factor to augment the action of insulin, and thus influences carbohydrate, protein, and fat metabolism (the biologic active chromium-containing species has not yet been identified). Since absorption of chromium(III) is very low, nutritional scientists have looked for a way to enhance its bioavailability.  Picolinate is simply an organic ligand that enhances absorption of chromium from the digestive tract.