Nutrition is a key determinant of health, wellbeing and aging. We want to understand how animals decide what to eat and how these decisions affect the fitness of the animal. To achieve a mechanistic, integrated, whole-animal understanding of nutritional decision-making we work at the interface of behavior, metabolism and physiology in the adult fruitfly. The powerful neurogenetic tools available in model organisms allow us to identify molecular as well as circuit mechanisms involved in producing the appropriate behavioral response to a specific need of the fly. We also dedicate a significant effort to the development of novel, automated and quantitative behavioral assays to understand the behavioral strategies used by the fly to make the right nutritional decisions. The combination of powerful molecular circuit manipulations, sophisticated behavioral analyses, and imaging approaches allows for a mechanistic understanding of how neuronal circuits control nutritional decisions to regulate important traits such as aging and reproduction.