Provided herein are methods and compositions for treating or preventing metabolic disorders, such as obesity and diabetes. Methods may comprise modulating the activity or level of a sirtuin, such as SIRT1 or Sir2. Exemplary methods comprise contacting a cell with a sirtuin activating compound, such as a flavone, stilbene, flavanone, isoflavone, catechin, chalcone, tannin or anthocyanidin, or an inhibitory compound, such as nicotinamide.