Abstract: The present invention provides a polynucleotide (hcap) isolated from a breast tumor library which identifies and encodes a human cachexia-associated protein (HCAP). The invention provides for genetically engineered expression vectors and host cells comprising the nucleic acid sequence encoding HCAP. The invention also provides for the therapeutic use of purified HCAP in the treatment of severe or moderate obesity, and for the therapeutic use of antisense molecules, antibodies, antagonists or inhibitors in the treatment of tumor-induced cachexia. The invention also describes diagnostic assays which utilize diagnostic compositions comprising the polynucleotide, or fragments thereof, or antibodies which specifically bind to the polypeptide.