Researchers put a large bowl of M&Ms candies in an apartment lobby with a quarter-cup spoon half the time, and a tablespoon the other half. After 10 days, the research found that people took two-thirds more M&Ms by weight on days when the bigger spoon was offered. Similar experiments featuring large and small Tootsie Rolls and pretzels yielded similar results.
"Whatever's served on your plate, it just seems locked in our heads: That's a meal," says researcher Andrew Geier. "Unit bias" -- determining appropriate portion size based on container size -- likely differs by culture, Geier says. For example, French yogurt containers are about half the typical size in America, but French people don't buy more containers to make up the difference.
Some food manufacturers have started manufacturing 100-calorie packets of food to help combat the obesity epidemic, which may have been partly brought on by the "super-size" trend of fast-food restaurants.
Geier recommends that dieters consciously take more control over their own portion sizes by using smaller serving dishes and asking restaurants to pre-package half of an order to take home. He also says food manufacturers could help by more prominently displaying serving sizes, since single packs of many manufactured foods and beverages contain much more than a single serving.
"The growth of portion sizes in America perfectly reflects the growth of Americans' waistlines," explains Mike Adams, holistic nutritionist and consumer health advocate. "The portions served to a single customer in American restaurants would be considered a family meal in other countries," he added.
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