White adipose tissue (WAT) primarily stores fat, while brown adipose tissue (BAT) bums fat.The amount of BAT is inversely correlated with BMI, suggesting it may play a role in metabolism.The recent description of BAT in humans has led to the realization that activation of BAT could facilitate additional daily energy expenditure of at least 5 kg per year.Thyroid hormone regulates differentiation of brown fat; we have found that TRβ specific ligands increase brown fat in obese mice without causing hyperthyroidism.These TRβ agonists have been shown to lower cholesterol by 40% in humans, an effect that is additive to that of the statins.Development of individualized strategies to regulate brown fat development and activity will be an important tool in designing weight loss strategies as the worldwide epidemic of obesity is precipitating a new epidemic of CVD.