A mammalian adipocyte-specific polypeptide, termed p154, is expressed in high quantities in adipogenic cell lines after cell differentiation and is abundant in the fat pads of normal and genetically obese mammals. The murine and human polypeptide, DNA and RNA molecules coding therefor, methods for its preparation, and antibodies specific for the polypeptide are also disclosed. Methods for determining the susceptibility of a subject to obesity are based on measuring the levels of the adipocyte polypeptide in a biological fluid or tissue extract or by measuring mRNA encoding the polypeptide in cells of the subject. Methods of evaluating an anti-obesity drug comprise contacting the drug with an adipocyte in vitro and measuring the amount of the adipocyte polypeptide or mRNA produced by the adipocyte. Methods of treating a subject with obesity comprise administering the above antibody or blocking the expression of the p154 gene.