Over the past decade, studies in nuclear medicine using positron-emisson tomography in conjunction with computed tomography (PET/CT) clearly revealed the presence of brown adipose tissue (BAT) in adult humans. Last year, highly publicized papers suggested a potential role for BAT to regulate not only human body temperature but possibly energy balance. Whether BAT can be up regulated in adult humans remain to be shown? Furthermore, the potential role of BAT in the regulation of energy balance needs to be investigated in response to overfeeding.