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Unformatted text preview: Central nervous system control of food intake and body weight G. J. Morton 1 , D. E. Cummings 2 , D. G. Baskin 2,3 , G. S. Barsh 4 & M. W. Schwartz 1 The capacity to adjust food intake in response to changing energy requirements is essential for survival. Recent progress has provided an insight into the molecular, cellular and behavioural mechanisms that link changes of body fat stores to adaptive adjustments of feeding behaviour. The physiological importance of this homeostatic control system is highlighted by the severe obesity that results from dysfunction of any of several of its key components. This new information provides a biological context within which to consider the global obesity epidemic and identifies numerous potential avenues for therapeutic intervention and future research. T he apparent ease with which we decide whether or not to eat an appetizing food testifies to the efficiency with which the central nervous system (CNS) processes information of sur- prising variety and complexity. With the aid of cognitive, visual and olfactory cues, food items must first be identified and distinguished from a nearly infinite array of potentially toxic environmental constituents. Using taste information, the food’s palatability is then assessed and integrated with both short- and long-term signals regarding nutritional state. One consequence of this integration is that the drive to eat decreases as food is ingested (termed ‘satiation’), ensuring that the amount consumed in a single meal does not exceed what the body can safely handle. Changing energy requirements is another factor that can influence food consumption. Through a process known as energy homeostasis, food intake is adjusted over time so as to promote stability in the amount of body fuel stored as fat. In this way, through diverse blood- borne and afferent neural signals, information regarding nutrient status and energy stores is communicated to the brain where it is integrated with cognitive, visual, olfactory and taste cues—all happening unconsciously, before the first bite is taken. Here we describe CNS mechanisms that regulate food intake, and review evidence that in response to reduced body fat stores, adaptive changes occur in neuronal systems governing both food-seeking behaviour (important for meal initiation) and satiety perception (important for meal termination). The net effect is that in response to weight loss, both the motivation to find food and the size of individual meals tend to increase until energy stores are replenished (Fig. 1), and mutation of any of several key molecules involved in this process has been shown to cause severe obesity in both animal models and humans. Despite this progress, the many fundamental questions remaining unanswered represent rich opportunities for future study....
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- Winter '08