Insulin levels, hunger, and food intake: an example of feedback loops in body weight regulation.

The paper reviews studies considering whether hyperinsulinemia, and its resultant effects on adipose tissue mass, can alter perceived hunger, taste, and food consumption. It also describes work addressing the reciprocal question of whether cues associated with food can affect insulin response. Specifically, four general categories of studies are presented. First, studies considering the causes and physiological consequences of chronic hyperinsulinemia are reviewed. Second, work investigating environmental and cognitive influences on insulin secretion are described. These show that high acute levels of insulin can be produced by simply seeing and thinking about food and that individuals showing this response show a greater tendency toward weight gain in a food-abundant environment. Third, studies are covered in which direct manipulations of insulin level, controlling for blood glucose, are performed. These experiments show that elevations in insulin produce increased hunger, heightened perceived pleasantness of sweet taste, and increased food intake. Finally, a study is described that considers how different insulin levels, produced by the type of food ingested, may affect subsequent food intake. Together, these studies show that "overeating" is caused by a complex feedback system of environmental, behavioral, and biological factors.