In 1551, the Swiss naturalist Konrad Gessner first described brown adipose tissue (BAT) as being __neither fat, nor flesh (nec pinguitudo, nec caro), but something in between__. Now, some 460 years... Show moreIn 1551, the Swiss naturalist Konrad Gessner first described brown adipose tissue (BAT) as being __neither fat, nor flesh (nec pinguitudo, nec caro), but something in between__. Now, some 460 years later, we know that Gessner had guessed the origin of brown adipocytes correctly. A unique property of the brown adipocyte is its capacity to dissipate energy stored in triglycerides (TG) as heat, which is mediated via the uncoupling protein UCP1. The recent discovery that active BAT is present in human adults meant the beginning of an exciting new area in metabolic research. BAT is currently regarded as a potential target to combat obesity and related diseases by inducing a sustained increase in energy expenditure. Interestingly, South Asians have lower energy expenditure, which may thus theoretically be caused by a reduction in BAT activity. The studies of which the results are described in this thesis were aimed at 1) gaining more insight into the physiology of BAT, 2) identifying novel tools and targets that may activate BAT, and 3) investigating the involvement of BAT in metabolism in humans with a focus on potential differences between South Asians and white Caucasians. Show less