Despite all the jawboning and gibberish about weight control, most Americans are still carrying around a few extra pounds because we lack the willpower to be careful about what and how much we eat. Right?
Not exactly, according to one major research program. What's also going on is a bit of trickery. And not just by the fast food industry. Our own brains trick us into eating more than we should.
Brian Wansink of the University of Illinois at Urbana-Champaign has made a career out of tricking people into thinking they are eating less than they really are.
Wansink, who holds an odd combination of positions at the university, including professor of marketing and professor of nutritional science, arrived at his conclusions after sticking bowls of jelly beans and M&Ms under people's noses, getting others to eat stale popcorn that's two weeks old, and even rigging up soup bowls that replenish the soup as it's being consumed, without the knowledge of the consumer.
The findings, in a nutshell, are pretty basic:
If your dinner tonight includes a lot of variety, chances are you're going to pig out.
If there's food readily available, chances are you're going to eat it. It's sort of a takeoff on that old proverb, if you serve it, they will come.
And if you think there's more there to eat, you're probably going to eat more. Even if it's stale popcorn.
What all that suggests, Wansink says, is the "hidden persuaders" that compel us down the road to obesity are "incredibly powerful" and "really, really subtle."
The findings strike at the core of why so many people are overweight these days.
"Most of us do a pretty decent job of deciding what we are going to eat," he says. "But we do a really bad job of deciding how much."
There's nothing wrong with having an occasional slice of pizza, he says, but we don't have to eat the whole platter. Yet if there's enough pizza to go around, chances are we will do just that.
The most striking feature of Wansink's research is the revelation that even something as simple as color can make a profound difference.
Wansink and Barbara E. Kahn, a professor of marketing at the University of Pennsylvania, found that people eat far more jelly beans, or M&Ms, if they are offered in many colors than in just a few. The multiplicity of colors suggests variety, even if they all taste the same, and variety suggests abundance, leading to increased consumption.
In a series of studies, involving more than 500 persons, the researchers found that persons who were offered six colored flavors of jelly beans mixed together in the same bowl ate 69 percent more than when the colors were placed in separate bowls. No difference in the jelly beans, but when the colors were mixed together it looked like a lot more, and thus a huge difference in the number eaten.
And here's a real killer statistic. Participants in other studies were offered M&M candies to chomp on while watching a movie. In some cases, the bowl contained 10 colors of M&Ms. In others, it contained seven.
Seven still seems like a high number, but the difference in the number eaten is astounding. Persons who were offered 10 colors ate 43 percent more than those offered seven.
"There are two things going on here," says Wansink, who trained initially as a consumer psychologist. "Anytime we see more variety, we anticipate we are going to enjoy it more. Since we anticipate we are going to enjoy it more, we end up taking more.
"The second thing is more insidious. We're pretty bad at deciding how much we are going to eat. We don't know what an appropriate amount is. So we look for some sort of cue as to what would be normal to take. And in the case of jelly beans, if there's a whole lot, it raises the estimate of what you believe is typical for somebody to take. If there's a whole lot of variety there, it's normal for me to take more."
We perceive variety, even if only in color, as meaning there's more available, even if the total number is actually the same. So if there's more there, it's OK to take more, although one of the studies suggested that if we think we might be depriving someone else of jelly beans, we might back off a little. It's not certain yet whether that was because the participants didn't want to eat someone else's candy, or they just didn't want to appear piggish, but the evidence suggests the latter.
There appears to be no limit in how far Wansink will go to understand our metabolic trickery. In one study, he designed a refillable soup bowl. Hidden tubes refilled the bowls so slowly that the participants didn't see it. Women ate 30 percent more soup if they had a refillable bowl than participants who had a regular bowl. Men ate 40 percent more. When asked later how much they thought they had eaten, there was no significant difference between those with, or without, refillable bowls. That suggests that when we are trying to determine how much we have eaten, we may be clueless.
Even the size of the container can make a difference. In one study the researchers gave participants buckets of 14-day-old popcorn. Some were given a large bucket, others a medium bucket. The stuff "tasted terrible," Wansink says, but people with large buckets ate 31 percent more than those with medium buckets, but both groups thought they had eaten about the same.
So where does all this leave us?
If there's more variety available, you'll probably eat more, so don't put a little bit of everything on your plate. Stick to a couple of items. Put the cheesecake where it's out of reach, and pull the broccoli closer. And put your meal in a smaller bucket.
Oh, and beware of jelly beans of many colors.
Lee Dye’s column appears weekly on ABCNEWS.com. A former science writer for the Los Angeles Times, he now lives in Juneau, Alaska.