Identifying safe/effective methods of regulating obesity associated weight gain has been problematic. Our technology represents methods/compositions for weight regulation and energy metabolism. We identified ligands, B-cell activating factor (BAFF), a proliferation-inducing ligand (APRIL) or their modulators, that prevent obesity. Animals expressing high levels of BAFF and given a high fat diet had significantly less weight gain compared to wild type. The prevention of diet-induced weight gain was dose dependent. Metabolic indicators such as glucose dysmetabolism, oxygen consumption and mitochondrial respiration demonstrate that BAFF regulates metabolic efficiency through modulation of brown fat thromogenic activity. These ligands represent a new method of regulating obesity.