Understanding the mechanisms governing the acquisition of white and brown adipocyte phenotypes might have implications for the physiopathology of, and therapeutic strategies for obesity. Peroxisome proliferator-activated recetor gamma (PPARgamma) and its coactivators, PGC-1alpha and SRC-1, influence brown adipocyte metabolism and development. Ectopic expression of PGC-1alpha induces the expression of brown adipocyte genes in human white adipocytes. The changes in gene expression promote stimulation of fatty acid oxidation. There is now evidence to support the concept of an alteration in energy balance through a conversion of white to brown adipose tissue.