The Fate of Fat: A Response

Brown adipose tissue (BAT) activity increases energy expenditure and therefore may facilitate weight loss. The principal physiological trigger for its activation is stimulation of the sympathetic nervous system by decreased ambient temperature. Also, direct pharmacological stimulation of the sympathetic nervous system activates BAT, but sympathomimetics up to now have had only very limited success as weight-lowering agents. More recently, components of other signaling pathways that trigger brown adipocyte development and activity have been investigated as potential treatment targets. These pharmacological options are far from the bedside since safety issues need to be clarified as well as the potentially important role of counter-regulatory energy-sparing mechanisms attenuating the negative energy balance achieved by BAT activation in the long term. However, BAT remains a very important candidate target for antiobesity treatment, a field in which alternative approaches have proved disappointing. Importantly, physical exercise is a nonpharmacological intervention which has the potential to activate BAT, promotes weight loss, has beneficial metabolic effects and may even slow the rate of aging.