Obesity: Increasing Awareness of Novel Environmental Factors

Over the past 20 years, the molecular underpin-nings of energy homeostasis have come to light(1–4) at a rate strikingly similar to that of therising prevalence of obesity (5, 6). The fact that one is statistically more likely to be overweight or obese in the U.S. today has profound ramifications for basic scien-tific research, translational research, public policy, and our health care economy. Homeostatic regulation of feeding. Current obesity statistics generate a striking contrast to abundant experi-mental evidence indicating that body adiposity is (or can be) a remarkably tightly regulated physiological variable (7–9), much like blood glucose concentration. Studies in rodent models, many of which have been confirmed in humans, have identified a plethora of humoral signals, neuropeptides, brain nuclei, and metabolic pathways in-volved in the precise physiological mechanism termed energy homeostasis (10). Primitive brain structures in