People who thought they ate more felt less hungry later.
PROBLEM: As anyone who's had a Man Men-style lunch followed by a Mad Men-style dinner knows, the connection between our brain and stomach is not simple or logical.
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METHODOLOGY: University of Bristol provided 100 volunteers with lunch, with either a large or small portion of tomato soup as an appetizer. But, as with all free lunches, there was a catch: the bowls had a secret attachment capable of pumping soup in or out without the participants noticing. What they thought they were eating was therefore different from what actually ended up making it into their stomachs. Immediately following the meal, and for the next three hours, they were asked to evaluate their levels of hunger and fullness.
RESULTS: Right after they finished eating, the participants seemed to be in touch with their stomachs: They reported levels of hunger proportional to how much they had eaten. But the brain-stomach line of communication weakened as time went on, and 2 to 3 hours later, memory took over. The participants who thought they'd had a larger portion of soup felt less hungry for another meal. A full 24 hours later, when again confronted with the two portion sizes, the ones who thought they'd had the larger portion believed that it was a sufficient size for them. In other words, they remembered it as being filling, even though it wasn't.