Ivar Rønnestad has been involved in studies of physiology of fish since 1988. His main research interest is nutritional and digestive physiology of marine fish, previously mainly the larval stages, but recently also ongrowing and adults. He is currently working with peptide hormones involved in regulation of digestion, energy homeostasis and appetite, the Gut-brain axis, GI-tract physiology, transporters, nutrient sensing and amino acid metabolism.