Using an eye-tracking device, researchers from Minnesota also found that the average consumer only reads the top part of a food content label.
They studied 203 people while looking at 64 different grocery products on a computer screen.
The Journal of the American Dietetic Association published the results.
In the study, participants were asked to view three elements on a typical food product - the nutrition contents label, a picture and list of ingredients, and a description of the product with price and quantity information - on the left, on the right or in the centre of the packaging.
One third of the participants each saw the nutrition label in one of those positions and were asked whether they would consider buying the product.
Participants were aware that their eye movements would be tracked, but unaware that the study was investigating nutrition information.Position test
When the nutrition contents label was presented in the centre, subjects read one or more sections of 61% of the labels compared with 37% and 34% of labels among participants randomly assigned to view labels on the left and right hand sides of the screen.In addition, labels in the centre of the product were seen to receive more than 30% more viewing time than the same labels when positioned to one side of the product.
The researchers also observed that most consumers view the contents of the label nearest the top more than those at the bottom of the label.
The study says that many more participants said they looked at the content of the nutrition labels than actually did when their viewing of the labels was tracked and measured.
Only 9% of participants actually looked at the calorie count for almost all products in the study, compared to 33% who said they did when asked.
Researchers Dan Graham and Robert Jeffrey, from the division of epidemiology and community health at the University of Minnesota, said: "The results of this study suggest that consumers have a finite attention span for Nutrition Facts labels.
"Although most consumers did view labels, very few consumers viewed every component on any label.
"These results differed from the self-reported survey responses describing typical grocery shopping and health behaviours submitted by the participants."They also said the location of the labels on the packaging made a difference.
"Consumers are more likely to view centrally located labels and nutrients nearer the label's top.
"Because knowing the amounts of key nutrients that foods contain can influence consumers to make healthier purchases, prominently positioning key nutrients, and labels themselves, could substantially impact on public health."
A spokesman from the Food and Drink Federation said they were aware that consumers often do not read labels.
"Any research that adds to our understanding of what would encourage consumers to use the information provided is welcomed.
"The transferability of this research to the UK shopping experience is unclear, as the study is based on computer simulation and uses information in a format that is quite different from what is found on packs in the UK."
But she said: "We support the provision of clear, simple front of pack nutrition labelling which the authors conclude would address the concerns raised by their research."