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Why New York City’s Big Gulp ban could be a big success

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Watch out, New York City: Mayor Mike Bloomberg is coming for your Matt Rourke AP Big Gulp. The mayor of America’s largest city has proposed to ban the sale of sugary drinks larger than 16-ounces (that would be the size of a small McDonald’s soda). The ban could go into effect as soon as March.

Unlike previous attempts to regulate the consumption of calorie-heavy drinks, public health research suggests this policy has a decent chance at actually working.

Other attempts to regulate soda have come with mixed results. While many cities and states have begun taxing sugary drinks, research suggests that none of the new policies raise the price of soda enough to reduce consumption. When schools ban sugary drinks in their vending machines, students often make up for the lack of soda on campus by drinking more at home (or, in some cases, even setting up a sort of black market for the calorie-dense contraband).

Portion size, on the other hand, has consistently been shown to affect how much we eat. In one well-known experiment, Philadelphia moviegoers were given either a medium or large bucket of stale, two-week old popcorn. Those with the large bucket ate 33.6 percent more popcorn, despite the fact it tasted pretty awful. When the package size of a snack food is doubled, calories consumed tend to go up by about a third.

“The more general explanation of why large packages and portions increase consumption may be that they suggest larger consumption norms,” writes Cornell University’s Brian Wansink, who has pioneered much of the research on food portion size. “They implicitly suggest what might be construed as a “normal” or ‘appropriate’ amount to consume.”

On the flipside, when portions get reduced, calorie consumption goes down. Belgian researchers recently looked at what happened when they cut a group of schoolchildren’s cookies in half. They found that the simple act of splitting cookies into smaller pieces — even while offering kids the same total number of calories — reduced consumption by 25 percent.

Portion sizes have spiked in the United States over the past few decades. The average fast-food soda is now seven times as large as it was in the 1950s. Bagels are about twice as large as they were in the 1970s; muffins, meanwhile, have grown threefold. Food research suggests that a law reversing this trend has a pretty decent shot at changing how many calories New Yorkers consume.

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