The role of nutritional information in human energy intake regulation

Previous research has shown that over time, humans can develop learnt associations between the sensory profile of a food and the energy it contains. These associations are then used to guide appetite for the same food in future situations. However, whether more acute, explicit information relating to the nutritional content of food can also shape eating behaviours in non-dieting individuals remains undecided. Following a review of previous literature, several methodological questions were raised relating to the effectiveness and validity of experimental manipulations used in some previous studies. The main aim of this thesis is to re-assess whether nutritional information could influence eating behaviours when these factors have been taken into consideration. In two initial experiments designed to address these issues, an interesting association was observed between participants' initial expectations of a preload and their ability to compensate for covert manipulations of its energy content. In order to further investigate this association, measures were developed based upon psychophysical analysis to provide an alternative method of measuring expectancies of the satiating efficacy of a food. The use of this measure allowed a quantifiable measurement of a participant's expectancies towards a food, while lessening the risk that demand effects were contaminating results. The final experiments of this thesis then re-examined the earlier observation that expectations of foods could mediate the regulatory responses that ingesting the food creates. The observed results did not support the proposal that expectancies of a preload were mediating compensatory ability by prompting attention towards visceral cues. Instead, results suggested that enhanced compensation was observed when participants were provided with an unexpected deficit in energy intake, rather than an unexpected surplus. This introduces the concept that an individual's short-term compensatory ability may be partly determined by pre-existing expectations about the food they are eating. The implications of this finding with regard to dietary preloading paradigms are discussed, and the possibility that this mechanism could explain the poor compensatory ability often associated with liquid loads is explored