CHAMPAIGN, Ill. - On a brisk fall morning, professor Brian Wansink welcomed four graduate students to his lab for what they thought was a taste test of tomato soup.
Unbeknown to the students, two of the four soup bowls were rigged to remain full, fed by hidden tubes. Twenty minutes later, the two students were surprised to learn their bowls had supply holes in the bottom and that they had eaten a third more than their colleagues.
That test is one of the experiments the University of Illinois' Wansink has conducted to figure out why people often eat more than they should, a concern when the medical community, the food industry and the government are under pressure to figure out why so many Americans are overweight and what can be done about it.
Wansink is among researchers nationwide who are studying how external factors from packaging to advertising to dining companions influence eating behavior. Experiments show that people do not necessarily stop eating when their stomachs tell them to and in some cases offer lessons that could help to curb the obesity epidemic in America. "People believe they're pretty good at calibrating what they eat," said Wansink, 43, who studies the psychology of food.
"I don't think they are. I think they rely on benchmarks, essentially the fill level of the bowl. There tends to be this visual cue that you're full."
During two years of Wansink's soup experiment, students with bottomless bowls tended to eat 40 percent more than test subjects with regular bowls.
"I wasn't aware of it," said Nina Huesgen, one of the students with a trick bowl. "That's why I feel so filled up, I guess."
Jason Stokes, who was similarly duped, said, "I did notice that my bowl level wasn't going down very much, but I thought that was because I wasn't eating very much."
The soup test is one of the methods Wansink has used to show that people often struggle to control their eating. People will shovel in a bucket of popcorn even if it's stale, and they'll gobble one candy after another if it's within arm's reach, Wansink has found.
The research by Wansink, a professor of marketing, nutritional science and agricultural economics, is particularly relevant because recent studies have shown that portions in restaurants and in homes have increased in the last few decades, most notably in "super-size" fries and soft drinks offered by fast-food restaurants.
Recognizing the importance of portion size, the federal government is reworking the serving-size section of the nutrition facts label on food packages to try to make it more useful to consumers. The current description of serving sizes is so confusing that consumers may be underestimating how much they are eating, the Federal Trade Commission said in a recent letter to the Food and Drug Administration, which had sought comment from other federal agencies on controlling obesity.
The FTC also questioned whether serving-size information on the food label was "sufficiently clear and prominent."
Some argue that the food industry should help by crafting smaller portions in supermarkets and in restaurants. But persuading food packagers to encourage less eating will be a tough sell, analysts say, because companies make more money if they sell more food.
Some nutritionists say the increase in portion size has fueled the obesity epidemic, but Barbara Rolls, a professor of nutritional sciences at Penn State University, said it is difficult to prove that the increase in portion size causes obesity.
The focus on where and how people eat needs to continue, said Rolls, who has conducted research similar to Wansink's.
"I think it needs to be easier for people to eat healthier," she said. "It's too easy for us to eat huge portions of high-calorie food.
In Rolls' research, she offered men and women different sizes of submarine sandwiches over four days. When served a 12-inch sandwich as compared with a 6-inch sandwich, men ate 56 percent more than the men given a 6-inch sandwich while women served the longer sandwiches ate 31 percent more than their counterparts who received the shorter sandwiches.
Wansink said he believes portion size is a factor that contributes to obesity, along with such features of modern life as elevators and computer games that discourage exercise.
"In the obesity war, portion size is the first casualty," said Wansink. "It's easy to point at, and we don't have to take responsibility because we can blame the restaurant or the packaged food manufacturer."
Wansink, who founded the University of Illinois' Food & Brand Lab, suggested that the federal government, which is in the process of revising the nutrition label on the side of packaged foods, could reconfigure the label so that consumers can better relate what and how much the are eating to their weight.
For example, instead of stating that a handful of granola has 200 calories, the label instead could say the consumer would have to walk two miles to burn it off.
As for ways the food industry could help, Wansink conducted an experiment that people who have stuffed themselves on potato chips might appreciate.
He offered three different groups Lay's Stax potato chips, a product that boasts "The crispy crunch will keep you coming back for more."
The first group received regular chips; the second got chips in which every seventh chip was red, and the third were served chips in which every 14th chip was red.
Without being told the reason for the red chips, participants nonetheless used them as a guidepost for how much to eat, Wansink said. The participants who ate the least had the potato chips in which every seventh chip was red, followed by the group in which every 14th chip was red.
"With chips, we kind of eat until we feel sated," he said. "But what happens if in a very in-your-face kind of way at the seventh chip there's a divider and you say, `Hey, how many have I eaten?' All of the sudden, it's an abrupt way to monitor how much you ate."
Wansink's research has produced some common-sense tips for weight-conscious consumers.
Office secretaries ate 25 percent more candy when it was on top of their desk rather than in a desk drawer. People who drank out of short, fat glasses consumed considerably more than those who used tall, skinny glasses, even though the glasses held the same amount.
"The tendency we have is to focus on heights instead of widths," Wansink wrote in a report on the study. "That's why, for instance, people say,
Boy, is the St. Louis Arch high.' But they never say,Boy, is it wide,' even though the dimensions are identical."
His analysis of comfort foods, meanwhile, found that women felt better about themselves after they ate snack food such as brownies or cookies, while men were soothed by hardier fare such as pizza or steak.
The women surveyed preferred snack foods because they didn't require much work, whereas they associated meals with cooking and cleaning up, Wansink said. The men surveyed favored meals because they conjured up the image of someone preparing the food for them, he said.
Wansink also found that both men and women feel better after eating small amounts of comfort food.
"You don't have to eat the whole pizza," he said. "People get psychological comfort by eating small amounts of these comfort foods."
But as Wansink has seen again and again, many consumers cannot stop with small amounts, a problem he attributes in part to the time-honored exhortation to eat until your plate is clean. People who are given larger portions eat more even if the food tastes bad, he said.
In one of Wansink's more revealing experiments, he offered free popcorn to moviegoers at a $1 movie theater outside Philadelphia. The movie "Stargate" was showing, and Wansink told the moviegoers the free popcorn was part of a celebration of the theater's anniversary. Half the audience was given fresh popcorn, either in small containers or in jumbo buckets; half received 14-day-old popcorn in small and jumbo containers.
"We had them write down what they thought about the popcorn, and 82 percent of the people who were given the old popcorn said it was terrible," Wansink said. Nonetheless, the moviegoers with the jumbo buckets of stale popcorn ate 33 percent more popcorn than those with the smaller container.
In the soup experiment, Wansink and his colleagues had to work out some early kinks before they could gather reliable data. During one taste test, the tubing came loose, causing one of the bottomless bowls to drain like a bathtub onto the floor; clamps are now used to hold the tubing in place.
Other problems surfaced because the level of the soup bowls and the stockpot were not calibrated to make sure the soup flowed properly through the tubing.
On one occasion, a student's soup started bubbling because of an imbalance between the stockpot and the bowl, said James Painter, chairman of Eastern Illinois University's Family and Consumer Sciences Department who collaborated with Wansink. Another time, a student who wasn't eating much soup was stunned to see her soup rising in the bowl; the experiment was stopped when the bowl started to overflow.
On the other hand, at times the experiment has worked all too well.
"One guy drank almost a quart (of soup)," Painter recalled. " I said,
What were you doing?' And he said,I was trying to reach the bottom of the bowl.'"
(c) 2004, Chicago Tribune. Distributed by Knight Ridder/Tribune News Service.