The Clean Plate Club isn't just something desperate parents talk about to get kids to eat their dinners. A new Cornell University study finds that the average adult eats 91.7 percent of whatever he piles onto his plate.
"If you put it on your plate, it's going into your stomach," says Brian Wansink Ph.D., director of the Cornell Food and Brand Lab and author of the upcoming book Slim by Design.
For the study, published in the International Journal of Obesity, Wansink and his team culled data from 14 different eating studies that altogether observed 1,179 diners from seven countries (the United States, Canada, France, Taiwan, Korea, Finland, and the Netherlands), and recorded how much each person started off with and how much was left on their plates after the meal.
The results were largely the same regardless of gender and nationality: Overall, everyone ate about 92 percent of everything on their plates.
"So that's really bad news: If anything causes you to serve more than you otherwise would, you'll still eat 92 percent of it," says Wansink, who has previously found that people grossly over-serve themselves when using bigger bowls and plates, a problem in the era of ballooning portion sizes.
Does that mean we're all giant pigs? Not necessarily.
"For the most part, we're pretty well-calibrated and we know how much food it will take to fill us up," says Wansink.
The kind of food people are served themselves makes a difference—the healthier it is, the more we finish. People finished 91.2 percent of their plate when they were eating fruits, vegetables, whole grains, lean meats, or dairy, as opposed to only 80.6 percent for sweet or salty processed foods, fatty meat, or sugary and fatty dairy products like ice cream.
People also ate more when they consumed "continuous" foods—think spaghetti, applesauce, or ice cream—rather than food that comes in discrete units—carrot sticks, cookies, chicken wings. A lot more: 93 percent vs. 71.8 percent.
No one who's ever taken care of kids would be surprised to learn that children ate less from their plate (59 percent) than adults did, but every observational stand-up comedian on Earth is going to have to revise his repertoire when he learns that women ate slightly more of their meal (91.8 percent) than men did (90.3 percent).
The study debunks another myth—that people who eat dinner in front of the boob tube scarf down more—by noting that people who were alone and weren't distracted when they eat consumed noticeably more (97.2 percent) than those who were in the company of other diners or simply watching TV (88.8 percent). So maybe allowing smartphones at the table during family supper is actually a good idea?
Finally, people finished less of their food when merely snacking (76.1 percent) than when having a full-on meal (92.8 percent).
So does that mean that, if you're trying to lose weight, all your meals should consist of healthy foods that come in discrete units and are served on small plates while you're sitting in front of the television—say, radishes on tea saucers presented during a Downton Abbey marathon?
Of course not, Wansink says. You can be aware of how much you're actually eating—especially now that you're armed with the knowledge from his study.
"Just knowing that you're likely to consume almost all of what you serve yourself can help you be more mindful of appropriate portion size," he says.