Thinking you're feasting when you're actually fasting can trick your appetite, new research shows. In experimental settings, when people thought they'd eaten a much larger meal than they actually had, hours later they still reported feeling just as satisfied as those that chowed down on a full serving.

A team of experimental psychologists from the University of Bristol sought to figure out whether a memory of a recent large meal could affect how hungry a person feels. Their results, published on Wednesday in the journal PLoS ONE, suggest that it does.


"This study is exciting, because it exposes a role for cognition in the control of hunger -- appetite isn't governed solely by the physical size and composition of the meals we consume,” lead author Jeffrey M. Brunstrom said in a statement on Wednesday.


The researchers took 100 volunteers and showed half of them a portion size with either 300 milliliters (1.3 cups) or 500 milliliters (2.1 cups) of creamed tomato soup. What they didn't know was that the bowl was secretly attached to a pump that could be manipulated by an experimenter.


When the subjects sat down to eat their soup, the scientists could manipulate the pump to add or remove soup from the bowl. Some people that were shown 300 milliliters of soup ate 300 milliliters of soup; others ate 500 milliliters. Ditto for the group shown the larger portion size: Some subjects ate the amount they had been shown, while others were eating less, unbeknownst to them.


Subjects were asked to report their hunger levels just after they finished eating. These figures matched up with the satiation levels expected based on how much soup they had actually eaten. But about 2 or 3 hours after lunch, those volunteers that had seen the larger soup portion reported significantly less hunger than those that had seen the smaller bowl, irrespective of what they actually ate.


The feelings persisted until a day after the experiment, when more of the people that had been shown the larger soup portion said that a 500 milliliter serving would be enough to satisfy them.


“For the first time, this manipulation exposes the independent and important contribution of memory processes to satiety. Opportunities exist to capitalize on this finding to reduce energy intake in humans,” the authors wrote.


So, what could be the commercial applications of this work? Trick plates that make portions look bigger than they actually are? Intentionally leaky soup bowls? Time alone will tell.


SOURCE: Brunstrom et al. “Episodic Memory and Appetite Regulation in Humans.” PloS ONE 7:e50707, published online 5 December 2012.