People often have food leftovers, which may impact their eating behavior; given equal actual consumption, larger (vs. smaller) food leftovers made people feel they ate less; as a result, larger (vs. smaller) food leftovers led people to eat more and exercise less later

Out of proportion? The role of leftovers in eating-related affect and behavior. Aradhna Krishna, Linda Hagen. Journal of Experimental Social Psychology, https://doi.org/10.1016/j.jesp.2018.08.005

Highlights
•    People often have food leftovers, which may impact their eating behavior.
•    Given equal actual consumption, larger (vs. smaller) food leftovers made people feel they ate less.
•    As a result, larger (vs. smaller) food leftovers led people to eat more and exercise less later.
•    These findings have implications for the success of “Just Eat Half” interventions.
•    The findings also underscore the importance of portion-size oriented policy interventions.

Abstract: It is well known that growing portion sizes increase consumption, but grossly enlarged portions also cause consumers to face more and more food leftovers. Despite the relevance of food leftovers, downstream effects of having more food leftovers on consumers' affect and behavior are unknown. In five studies, the authors test the idea that consumers may judge their actual consumption by looking at their leftovers. As such, larger leftovers may reduce perceived consumption and also impact other eating-related behaviors. Using both real and imagined food consumption and leftovers, the authors find that, holding the absolute amount of food consumption equal, larger (vs. smaller) food leftovers lead to reduced perceived consumption. This difference in perceived consumption has consequences for people's motivation to compensate for their eating. Larger (vs. smaller) food leftovers cause them to eat more in a subsequent unrelated food consumption task, and also to exercise less in an explicit calorie compensation task. The psychological drivers of this phenomenon are twofold: larger leftovers reduce perceived consumption, which leads people to feel better about themselves; and feeling better about themselves, in turn, reduces people's motivation to compensate. This research reveals a previously unknown negative consequence of grossly enlarged portion sizes and informs research on perceived consumption.