The prevalence of obesity in developed countries is fast becoming a health issue on par with infectious diseases and malnutrition. Research in this area has grown substantially and includes the neurochemical pathways of the hypothalamus and its role in regulating energy expenditures in the body. This volume in the Progress in Brain Research series examines the emerging role of the hypothalamus as a crucial link between the sensing of nutrients and the control of insulin sensitivity, glucose uptake, and glucose production, the integrative role of the hypothalamus in thyroid and bone metabolism, the interaction between circadian information and energy metabolism, and the important interplay between the immune system and energy metabolism.