The present invention is directed to methods, kits and compositions for preventing or treating age-related conditions or metabolic disorders. The Klotho fusion polypeptides of the invention include at least a Klotho protein or an active fragment thereof. In one embodiment, the fusion polypeptide comprises a Klotho polypeptide, a FGF (such as FGF23) and (optionally) a modified Fc fragment. The Fc fragment can, for example, have decreased binding to Fc-gamma-receptor and increased serum half-life. The Klotho fusion proteins are useful in the treatment and prevention of a variety of age-related conditions and metabolic disorders. In another embodiment, the fusion polypeptide comprises a FGF (such as FGF23) and a modified Fc fragment.