transgenic animal models with single genetic defects can yield important information on adipose tissue biology and pathophysiological states, but may not always match the human disease. Thus, it is important that new relevant animal models employing more sophisticated strategies for gene inactivation or overexpression are developed to extend our understanding of the mechanisms underlying obesity and its metabolic consequences. Finally, a better understanding of the function of adipose tissue biology will likely permit more rational approaches in the prevention and treatment of excess and deficiency of adipose tissue.