Most people probably think they stop eating when they're full. They don't realize that feeling satisfied comes from a combination of signals, including how good the food tastes or how quickly certain hormones get released into the body. It may also depend on where they live.
In the diet world, there's long been talk about the French paradox. It's the idea that even though the French eat a lot of fatty cheeses, indulgent desserts and buttery pastries, they still have lower levels of obesity (as well as lower incidence of heart disease) than Americans. Experts believe that may be because the French eat smaller portions at meals or that they simply walk more than the couch potatoes in the U.S.
There may be another reason. A French friend of mine suggested that it's “because we know when to stop eating.” Mon dieu! Could it be that simple?
Knowing when to quit
In deciding when it's time to push away from the table, it seems that the French may be responding to different eating signals than Americans. In a recent study, researchers from my Cornell Food Lab asked 133 participants from Paris and 145 from Chicago to complete a brief survey on their food habits, posing the question “How do you know when you are through eating dinner?”
The Parisians said they knew they were through when they no longer felt hungry or when the food no longer tasted good to them. Their answers suggested that they're influenced by internal cues — whether they liked the taste of the food or whether they wanted to leave room for a later dessert — to tell them dinner's over.
In Chicago, it was a different ball game. The 145 Americans relied on external cues of satiety. They said they knew they were through eating when they cleaned their plate, when everyone else at the table was finished or when the TV show they were watching was over.
The Americans were more influenced by their environment than whether they were actually still hungry. Since most of the signals in our society, from TV commercials to our best friends, tell us to “eat, eat, eat,” it can be difficult to control intake if we're ignoring our own bodies.
The study, conducted by Collin Payne and Pierre Chandon and published recently in the journal Obesity, also found that, for both the American and French participants, the heaviest people tended to be the ones who relied on external cues to tell them when to stop eating.
How we respond to these eating cues can affect our weight. On average, the French had a lower body mass index than the Americans (20.7 compared to 23.6), although the majority of both groups were of normal weight. Both groups were of a similar demographic (age, gender and college educated). The leanest people in either cities were more likely to use internal cues to stop eating, while those who were overweight — whether French or American — were more influenced by their environment.
Mind your body not your plate
If you tend to be more like the group from Chicago than the Parisians, the easiest way to avoid overeating is to have the external or visual cues work for you. For example, use a smaller plate and put everything on your plate before you eat. Don't go back for seconds. And don’t eat while you watch TV.
The Chicago response of being full when the plate or bowl backs up previous research from my lab. In one study of 62 people we designed bowls that were secretly refilled from under the table. People eating from the bottomless soup bowls ate 73 percent more, but didn’t rate themselves as being any more full than people who ate from regular bowls.
If you want to avoid overeating, it's better to pay more attention to what your body is telling you than what's left on your plate.
Brian Wansink, Ph.D., author of "," is head of the U.S. Department of Agriculture's Center for Nutrition Policy and Promotion. He is also director of the Cornell Food and Brand Lab.