The circadian clock, light, and cryptochrome regulate feeding and metabolism in Drosophila.

Recent studies in mammals have demonstrated a central role for the circadian clock in maintaining metabolic homeostasis. In spite of these advances, however, little is known about how these complex pathways are coordinated. Here, we show that fundamental aspects of the circadian control of metabolism are conserved in the fruit fly Drosophila. We assay feeding behavior and basic metabolite levels in individual flies and show that, like mammals, Drosophila display a rapid increase in circulating sugar following a meal, which is subsequently stored in the form of glycogen. These daily rhythms in carbohydrate levels are disrupted in clock mutants, demonstrating a critical role for the circadian clock in the postprandial response to feeding. We also show that basic metabolite levels are coordinated in a clock-dependent manner and that clock function is required to maintain lipid homeostasis. By examining feeding behavior, we show that flies feed primarily during the first 4 hours of the day and that light suppresses a late day feeding bout through the cryptochrome photoreceptor. These studies demonstrate that central aspects of feeding and metabolism are dependent on the circadian clock in Drosophila. Our work also uncovers novel roles for light and cryptochrome on both feeding behavior and metabolism.