Appetite in the Brain
Appetite is defined as ‘a natural desire to satisfy a bodily need, especially for food’. The counterpart of appetite is satiety, which is the state of satisfaction that follows after the need for food is fulfilled. However, palatable food can be appetizing in the absence of hunger and people may engage in eating in the absence of hunger, i.e. in the absence of an acute need state. Appetite sensations are formed in the brain, through the integration of a multitude of neural and hormonal signals involved in the regulation of food intake. Measuring appetite objectively is inherently hard due to the complexity of its underlying determinants and accordingly there are multiple operationalizations of appetite. First, different terms and concepts used for describing and investigating appetitive sensations are introduced. Second, the regulation of food intake is addressed with a focus on what might ultimately drive food intake and body weight regulation. Finally, functional neuroimaging work on the neural correlates of appetite in the brain is discussed. In conclusion, what exactly drives the central regulation of food intake and how this is encoded in the brain has not been established. It is important to resolve this as it would provide novel and more effective ways of preventing and treating obesity. Food intake is so complex that this is likely to require personalized intervention strategies. Therefore, the interrelations between subject characteristics (genotype), food-induced brain responses and eating behaviour need to be unravelled further.