Quality and quantity of nutrients are key determinants of health and lifespan across phyla. Dietary proteins are of particular importance as many animals, including humans and Drosophila, cannot efficiently synthesize some of proteins´ building blocks, namely, essential amino acids (eAAs). Thus, animals and humans relay solely on protein intake to obtain them. However, each eAAs has different physiological roles and different effects on health-span. In order to overcome protein imbalance, animals can change their feeding strategy to increase protein consumption, even when only a single eAA is missing in their diet. However, the cellular and molecular processes leading to change in feeding preference to a specific food source upon a protein deficiency are still unknown. In this project our aim was to uncover the process of translating the need for any single eAA to a goal direct behavior towards foraging and consuming proteinaceous foods. The behavioral adaptation to diettary imbalance and the physiological importance of eAA are highly conserved, and gene regualtion is highly translatable across species. Thus, the identified mechanisms from this project shed light on global process underlying protein-related dietary perturbations and the relavant behavioral adaptations.