The present invention provides for systems, compositions, methods and kits for regulating energy metabolism in pets. The systems, compositions, and kits can comprise, and methods can make use of, pet foods, pet treats, pet supplements, and pet drinks. In one aspect, the invention provides for pet food, treat, supplement, and drink compositions that comprise a combination of (a) leucine, and (b) vitamin B6, or any precursors or metabolites of (a) or (b). These combinations may be effective for reducing weight or adipose volume in the pet. In another aspect, the invention provides for methods of regulating energy metabolism by the administration of one or more compositions comprising leucine, a leucine metabolite, and/or vitamin B6. The invention also provides for kits comprising compositions of leucine, a leucine metabolite, and/or vitamin B6 packaged in an oral dose form with usage instructions.
