People - especially overweight people - consume up to 50 percent more calories when they eat low-fat versions of snack foods than when they eat the regular versions, according to a new Cornell study.

Further, a companion study finds, when food labels show serving sizes on such packaged low-fat snacks as granola or chocolates, normal-weight people tend not to overeat them while overweight people do.

"This is a world of fat-free, carb-free and sugar-free products," says Brian Wansink, the John S. Dyson professor of marketing and of Applied Economics at Cornell. In fact, many low-fat-labeled foods have only about 30 percent fewer calories than their regular counterparts.

"Often, the fat-free version is not much lower calorie than the regular version," Wansink says. "Low-fat labels trick people into eating more than regular labels. But the cruel twist is that these labels have an even more dramatic impact on those who are overweight. They are at danger for really overindulging when they see something with a low-fat label. If we are looking for an excuse to eat, low-fat labels give it to us."

He recommends that low-fat-labeled foods post larger, more realistic serving sizes, which might deter people from eating too much by giving them a more accurate calorie count.

The study, conducted with Pierre Chandon, a marketing professor at INSEAD, an international business school in France, is published in the November issue of the Journal of Marketing Research and reported in Wansink's book, Mindless Eating: Why We Eat More Than We Think (Bantam, 2006).

Source: Cornell University