Most Americans clean their plates, no matter how full those plates are, a survey has found.

The findings, released by the American Institute for Cancer Research on Thursday, add to the debate over how much restaurants and fast-food outlets are contributing to the epidemic of obesity in the United States and elsewhere.

The institute's survey found that 69 percent of those polled finish their meals most or all of the time, even when the portions are huge.

"Fully 30 percent of Americans now say they generally base the amount of food they eat on the amount they are served," according to the institute, which promotes research on the links between diet and cancer.

"In a country where 64 percent of us are overweight or obese, there is an alarming tendency to overlook the sheer amount of food we're eating," Dr. Barbara Rolls of Pennsylvania State University told a news conference.

The report compiled information from two surveys involving 1,000 adults each. One was conducted in 2000 and the other in 2003.

In 2000, 7 percent of those surveyed said they ate their entire meal all the time when dining at full-service restaurants. That number rose to 37 percent in 2003.

"Scientific studies show that people can and do unconsciously consume more calories -- as much as 56 percent more -- when served larger portions," the institute said.

It cited a study published in 2002 in the Journal of the American Dietetic Association that found in 1955, a single order of fries weighed 2.4 ounces, compared to 7.1 ounces now.

Writing in the American Journal of Clinical Nutrition, Rolls and her colleagues said people ate 30 percent more macaroni and cheese when given the largest of four different portions.

Fewer than half of those tested noticed the differences in the portions they were served.

(Agencies)