There is a reciprocal interaction between diet and the chemical senses: sensations shape our dietary patterns, and diet, in turn, influences the way we sense food. Indeed, human and animal studies have shown that diet composition can regulate taste sensation and perception, but the causes and consequences of this chemosensory plasticity are still poorly understood. Over the last five years we have used the simple taste apparatus of the fly D. melanogaster to understand the molecular and neural mechanisms of diet-induced taste plasticity. We discovered that nutrients can directly regulate the responses of the taste cells and sensory neurons to sweetness via epigenetic mechanisms, and that chemosensory alterations change meal size and intake by affecting the central processings of sensory information by dopaminergic neurons. We will summarize these findings and present new data showing how a high-sugar diet induces lasting synaptic and morphological changes in the sensory neurons to blunt their output and dull behavioral responses to food.