The global epidemic of obesity: are we becoming more sympathetic?

The relationship between obesity and sympathetic nervous system (SNS) behavior has been controversial. Existing paradigms have been opposed in their views of the directional changes in SNS activity in obesity. In addition, limitations of previous approaches to assess SNS activity have produced inconsistent findings. However, the use of state-of-the-art neurochemical and neurophysiologic techniques has improved our current understanding of this issue. There is regional heterogeneity in the SNS activation associated with obesity, with the renal and skeletal muscle circulations, but not the heart, being targets for SNS activation. Abdominal visceral fat appears to be an important depot linking obesity and skeletal muscle SNS activation. The impact of this depot on SNS activity to the kidney or other regions is unknown. Future studies are needed to address this issue as well as the mechanisms and consequences of SNS activation in visceral obesity.