Because they use internal cues -- such as no longer feeling hungry -- to stop eating, reports a new Cornell study. Americans, on the other hand, tend to use external cues -- such as whether their plate is clean, they have run out of their beverage or the TV show they're watching is over.

"Furthermore, we have found that the heavier a person is -- French or American -- the more they rely on external cues to tell them to stop eating and the less they rely on whether they felt full," said senior author Brian Wansink, the John S. Dyson Professor of Marketing and director of the Cornell Food and Brand Lab in the Department of Applied Economics and Management, now on leave to serve as executive director of the U.S. Department of Agriculture's Center for Nutrition Policy and Promotion until January 2009.

The new study, an analysis of questionnaires from 133 Parisians and 145 Chicagoans about how they decide when to stop eating, is published in the December 2007 issue of the journal Obesity and online at http://www.obesityresearch.org/cgi/reprint/15/12/2920.pdf .

"Over-relying on external cues to stop eating a meal may prove useful in offering a partial explanation of why body mass index [a calculation based on the relationship of weight to height] varies across people and potentially across cultures," said co-author Collin Payne, a Cornell postdoctoral researcher. He stressed that further studies should following up with smoking behavior and socio-economic differences as well. "Relying on internal cues for meal cessation, rather than on external cues, may improve eating patterns in the long term.

Wansink, author of "Mindless Eating: Why We Eat More Than We Think," also conducted the study with Pierre Chandon, a marketing professor at INSEAD, an international business school in France.

Source: Cornell University