The Role of Brain in Energy Balance

Energy homeostasis is regulated by homeostatic and nonhomeostatic reward circuits which are closely integrated and interrelated. Before, during, and after meals, peripheral nutritional signals, through hormonal and neuronal pathways, are conveyed to selective brain areas, namely the hypothalamic nuclei and the brainstem, the main brain areas for energy balance regulation. These orexigenic and anorexigenic centers are held responsible for the integration of those signals and for an adequate output to peripheral organs involved in metabolism and energy homeostasis. Feeding includes also a hedonic behavior defined as food intake for pleasure independently of energy requirement. This nonhomeostatic regulation of energy balance is based on food reward properties, unrelated to nutritional demands, and involves areas like mesolimbic reward system, such as the ventral tegmental area and the nucleus accumbens, and also opioid, endocannabinoid, and dopamine systems. Herein, focus will be put on the brain circuits of homeostatic and nonhomeostatic regulation of food intake and energy expenditure.