Abstract: Currently, obesity research centers on ways to help people consume fewer calories, but in the wake of research into brown adipose tissue, new classes of drugs may be developed that will be able to increase brown adipose tissue activity and make it possible for obese individuals to burn the calories they take in more quickly. The fact that brown fat is found in large amounts in young, lean adults, that it is activated by cold temperatures, that it allows calories to be burned off instead of stored, and that a molecular switch may be present to convert white fat to brown makes this area extremely interesting and challenging to those who are in the front lines of anti-obesity research. The genes for activation of brown adipose tissue appear to have come to us with our mammalian heritage along with mammary glands and hair. Other mammals have made use of brown adipose tissue during hibernation, in surviving nocturnal and seasonal cold, and in surviving the cold stress brought about by the birthing process. Perhaps humans will soon be able to add another dimension to the list of survival tactics associated with brown adipose tissue as they learn how to turn it on in increasing amounts in order to stay fit, trim, and lean into adulthood and beyond.