(KTNV) -- A recent experiment put a group of hungry college students to the test. Without their knowledge.
Cornell University students were asked to help ABC News with a profile on their professor, Brian Wansink. He runs the Food and Brand Lab at Cornell.
It was really a demonstration about portion sizes.
Wansink offered lunch to the students, giving each one of them an 8 ounce portion.
Even though they all received the same amount, some were told that they were getting a half-sized portion, others were told they were getting a regular-sized portion, and the rest of the group believed they were receiving a double.
The groups that thought they were eating a smaller- or regular-sized portion cleaned their plates. The group that thought they had a double portion left food behind.
Wansink says this can explain why Americans are fat. Many people eat what they are served without thinking about how much they are actually eating.
This can be a problem especially when eating out because many restaurants serve huge portions.