Diabetes and obesity, two major public health concerns, are associated with increased risk for problems in multiple organ systems, including the central nervous system. The adverse effects of diabetes and obesity on cognitive functioning are increasingly well recognized. This special issue of Psychosomatic Medicine features the latest research linking diabetes, obesity, and brain structure, function, and metabolism and follows a special meeting on this topic organized by the American Psychosomatic Society in October 2013. Evidence for the increased prevalence of diabetes and obesity is reviewed as it relates to cognitive decline. These articles indicate that the age of onset of Type 1 diabetes may be relevant to future cognitive function and that disease duration of Type 2 diabetes and sociocultural factors are related to cognitive decline during the aging process. The hypothalamus and other neural circuits, notably the dopaminergic system that underlies feeding and reward-related aspects of food intake, are among the key factors involved in obesity. Research on the associations between obesity and cognitive function is described using the positive effects of weight reduction following bariatric surgery or behavioral methods. This special issue concludes with a conceptual framework for linking obesity and diabetes with accelerated cognitive decline as related to the aging process. The collection of articles highlights the importance of using a life span perspective to understand the influence of both Type 1 and Type 2 diabetes on brain metabolism, function, and structure. Moreover, these studies show that distressing environmental circumstances can adversely influence neurocognitive dysfunction associated with obesity and diabetes.