A novel protein and a process of producing the protein is provided. The protein is a glycoprotein having activity of suppressing the differentiation and/or maturation of adipocyte, having a molecular weight of about 45 kD under non-reducing conditions and about 28 kD and/or 23 kD under reducing conditions, and exhibiting affinity to heparin. A process of producing the protein comprising culturing human fibroblasts and purifying the culture broth by chromatography using an ion exchange column, affinity column, and reverse phase column.A cDNA encoding the protein and a process of producing the protein using the cDNA are also provided. The protein of the present invention is useful as a pharmaceutical composition for preventing or treating obesity or as an antigen for establishing immunological diagnosis, etc.