Brown fat is a specialized fat depot that can increase energy expenditure and 
produce heat. After the recent discovery of the presence of active brown fat in 
human adults and novel transcription factors controlling brown adipocyte 
differentiation, the field of the study of brown fat has gained great interest 
and is rapidly growing. Brown fat expansion and/or activation results in 
increased energy expenditure and a negative energy balance in mice and limits 
weight gain. Brown fat is also able to utilize blood glucose and lipid and 
results in improved glucose metabolism and blood lipid independent of weight 
loss. Prolonged cold exposure and beta adrenergic agonists can induce browning 
of white adipose tissue. The inducible brown adipocyte, beige adipocyte evolving 
by thermogenic activation of white adipose tissue have different origin and 
molecular signature from classical brown adipocytes but share the 
characteristics of high mitochondria content, UCP1 expression and thermogenic 
capacity when activated. Increasing browning may also be an efficient way to 
increase whole brown fat activity. Recent human studies have shown possibilities 
that findings in mice can be reproduced in human, making brown fat a good 
candidate organ to treat obesity and its related disorders.