How to change expected fullness? The role of familiarity and 'eating to fullness'

The fullness that a food is expected to confer appears to predict self-selected portion size. Indeed, ‘expected satiation’ is a better predictor than palatability and is closely associated with food reward. Given this, identifying factors that affect expected satiation should be given a high priority. Studies from our laboratory suggest that familiarity could be important. However, differences in expected satiation might also be explained by (i) the extent to which foods are eaten to fullness and (ii) macronutrient composition. In this study, participants (N = 302) were shown images of 40 test foods. In response to each food they rated expected satiation, completed a measure of familiarity, and indicated whether it had ever been eaten to fullness. Consistent with previous studies, familiarity was associated with higher expected satiation. However, ‘eating to fullness’ was an even better predictor. In every test food, eating to fullness was associated with higher expected satiation, and this was the case even after controlling for effects of familiarity. By contrast, macronutrient composition was a poor predictor of expected satiation. Together, these results illustrate the relative importance of prior experience and eating to fullness as determinants of expected satiation. More generally, they are consistent with our ‘expected-satiation drift’ hypothesis. Specifically, from a foraging perspective, we propose that novel foods should be expected to confer little satiation, and for this to remain the case unless experience teaches us otherwise. Our findings provide clear support for this hypothesis because expectations ‘shifted’ in only one ‘direction’. This research was supported by a BBSRC-DRINC grant (ref:BB/G005443/1). Copyright © 2011 Published by Elsevier Ltd.