Food Intake and Physiological Regulation: The Means and the End

Abstract

The independent life of animals requires the active regulation of many critical parameters of the internal status of the organism, in other words, their maintenance within a narrow range of defended values. From the early days of research into homeostatic mechanisms, it appeared that food intake (FI) is not one of such parameters. FI is one of many effector mechanisms that contribute to the regulation of several internal parameters, such as glycemia and adipose stores. The science of the last century has clarified the fine machinery of regulatory processes, both at the periphery and in the brain. Beyond the early notion of feedback loops triggering regulatory responses to existing need states, research has documented how efficient regulation rests on learned anticipatory responses, both physiological and behavioral, that are highly plastic and continuously shaped by the experience of environmental contingencies. Studies of eating patterns in free-living humans have revealed the significant influence of numerous factors, among which signals of physiological needs exert a modest role. In spite of the massive influence of environmental and social factors, regulatory adjustments can be detected in the FI of humans, including obese humans. These impressive developments in knowledge have paralleled an unprecedented increase in the frequency of obesity. In this field, knowledge does not equate power. Even in the obesogenic world, FI matches energy needs perfectly in many individuals. Understanding why regulation mechanisms allow body adiposity to drift upward in so many others remains a crucial question.