Although super-size really is super-size, very often companies will label their foods "small" or "medium," with their actual weight in units varying from anywhere between eight and 16 ounces - or even more. But reading "small" or "medium" actually has a huge effect on how people eat.

Researchers from the Cornell Food and Brand Lab wanted to understand this effect. They used lunch foods, such as spaghetti, in a one-cup size (small) and a two-cup size (large), and examined how people's eating habits changed when the cups were labeled in different ways. For some participants, the cups were labeled as "half-size" (small) and "regular" (large). Other participants were given cups that said "regular" (small) and "double-size" (large).

They found that people's eating habits did indeed change with how the labels read. When served the large portions of spaghetti, the participants ate more when they were labeled "regular" than when they were labeled "double-size." The researchers actually found that the participants who had the "double-size" plates left 10 times as much food on their plates.

Next, the researchers wanted to see if labels played a part in how much a person was willing to pay. In an auction-style experiment they had participants bid on portions. They found that participants were only willing to pay half the amount for a "half-sized" portion compared to a "regular" portion, while at the same time, they were willing to pay more for the "double-sized" portion even though it wasn't actually double sized.

The researchers concluded that it was the labels that ultimately indicated how much food was on each plate, rather than visual appearances, or a weighted amount. They also concluded that people adjust the amount they eat accordingly, meaning that even if it's an overly large portion, they will still eat it if they believe it is "regular" sized.

The researchers suggest standardization of food-label sizing in order to make it clear between consumer and producer exactly how much food is bought every time someone asks for a certain size.

Standardization of labels could have huge impacts on the way Americans eat. With the country's obesity rate rising again, knowing exactly how much food you're buying would mean better management of intake. According to a survey by the Gallup-Healthways Well-Being Index, obesity has risen in the U.S. to 27.1 percent, compared to 25.5 percent in 2008.