Is there a sympathetic regulation of the efficiency of energy utilization?

Brown adipose tissue, a well known effector of regulatory thermogenesis found in mammals, is unique in its ability to steadily increase its heat production several fold for very long periods of time. It constitutes a shunt of energy flow between food intake and heat dissipation, it is activated through its sympathetic nerve supply. There are evidence in the rat, that brown adipose tissue is activated following overfeeding, thus decreasing food efficiency and determining resistance to obesity. Genetically obese (ob/ob) mice fed and kept at 22 degrees C lack the possibility of activating their brown fat energy shunt; they are known to be poorly resistant to cold stress despite their large insulation. This is taken as a further circumstantial evidence of an overlap in thermal and food efficiency regulatory systems in rodents through sympathetically controlled brown fast as a common effector.