The present invention is based at least in part on the discovery of a role for the JNK signaling pathway in longevity. In particular, the present inventors have shown that overexpression of c-jun N-terminal kinase 1 (jnk-1) extends lifespan and that said extended lifespan is associated with DAF-16 phosphorylation by JNK-1 and the consequent DAF-16 localization to the nucleus. Accordingly, the present invention features methods of identifying modulators of longevity in assays featuring organisms and/or cells having a JNK signaling pathway and, optionally, an IR signaling pathway. Also featured is an in vitro method of identifying an agent capable of enhancing longevity featuring an assay composition having a JNK signaling pathway molecule and insulin signaling pathway molecule. Further featured are therapeutic methods for the use of JNK signaling pathway modulators to enhance longevity, to prevent or reduce obesity and to prevent or treat type II diabetes.