The prevalence of obesity has dramatically increased in western and westernized societies, making the disease the second leading cause of unnecessary deaths in the US. Obesity results from imbalanced metabolic regulation leading to excessive lipid storage. As important novel entities in metabolic regulation, taste receptors and their cells are critical elements that adapt the gustatory system to metabolic signals and vice versa. The role of taste receptor genes in gastrointestinal tissues, as well as their dynamic regulation in gustatory and non-gustatory tissues in response to metabolic cues, has become the focus of an entirely new and rapidly developing research field with impacts on fuel sensing, metabolic control, and ingestive behavior. This book reflects the recent scientific progress in the field of fuel sensing in the mouth, GI tract, and brain and examines the olfactory bulb as a potential metabolic sensor and the brain-gut endocrine axis. It also touches on relevant novel molecular and cellular mechanisms regulating lipid storage and metabolism and covers the identification and functional characterization of obesity genes. Lastly, it illustrates the use of insect models to study relevant problems of energy homeostasis.