Control of food intake. A physiologically complex, motivated behavioral system.

This article has examined the control of food intake as a physiologically complex, motivated behavioral system. During the past four decades, considerable progress has been made in understanding putative signals for hunger, satiation, and satiety, although hunger signals have proven to be more difficult to identify. The putative physiologic controls of food intake include positive and negative sensory feedback; gastric and intestinal distension; the effects of nutrients, nutrient reserves, and metabolism in producing signals to the liver or brain; and peptides and hormones released in the gastrointestinal tract or the brain. However, food intake is not influenced solely by physiologic signals for hunger, satiation, and satiety. To comprehend feeding behavior more thoroughly, current physiologic models must be extended to include modulating factors such as feeding-associated responses adapted through learning processes and the influence of circadian rhythms, which can be dominating over hunger, satiation, and satiety signals.