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.     

On the relationship between the menstrual cycle and the body weight and food intake of women

Body weight and food intake of women are analyzed over the whole menstrual cycle. Over 68-94 days body weight and food intake of eight women and three men are recorded. For food intake, a diary self-report method is used. The beginning of each woman's menstrual cycle is also recorded. Body weight and food intake are regarded as stochastic processes. The theory of time series and spectral analysis is applied. As opposed to the males, in the spectra of seven females, there is a peak at a frequency with the period of the respective females' menstrual cycles. There are no further consistent differences. This sine wave reaches its maximum two to three days before menses. The data suggest that, as a first approximation, the body weight of women during a complete menstrual cycle can be described by a simple sine wave. For food intake, the spectra show hardly any differences between females and males. However, it is shown that the same sine wave as in body weight is also contained in the food intake of seven females, reaching its maximum about four days before menses.     

The effect of anxiety on food intake in the rat

Three levels of anxiety were induced experimentally in rats. With hunger drive held constant, the effects of anxiety on the intake of food which had either a positive or negative incentive value were observed and compared. The results for the intake of food with positive incentive value showed eating to be increased above control level by a low level of anxiety, and slightly decreased by medium and high levels. On the other hand, a direct relationship was observed between level of anxiety and suppression of the intake of food with a negative incentive value. These findings were shown to be inconsistent with previous explanations of similar effects in terms of an interaction between relevant and irrelevant drives. An alternative explanation in terms of incentive was offered.