Diet & Fitness

Soda study shows limiting size makes us want to gulp more

April 10, 2013 at 5:17 PM ET

A month after a judge threw out New York City Mayor Michael Bloomberg’s proposed ban on large sodas, a new study has found that Americans not only love their sugary drinks, they buy even more of them when serving sizes are restricted.

“The motivation for this study was inspired by the proposed regulations to restrict soda sizes,” said Brent M. Wilson, lead author of the study published Wednesday in the open-access journal of the Public Library of Science (PLOS).

Conducted by the University of California at San Diego, the study concluded that restricting larger servings of sugary drinks in an effort to moderate them may actually induce consumers to buy even more.

Wilson did not say whether his findings were a repudiation of Bloomberg’s attempt to limit sugar intake for health reasons, but characterized the results as “information that policy-makers should take into account.”

Bloomberg’s much-ballyhooed ban on large sodas fell flat last month -- the day before going into effect -- when Manhattan Supreme Court Justice Milton Tingling dismissed the rule as “arbitrary and capricious.” He sided with soda companies and business groups that had taken the city to court.

The rule would have banned sales of sugary sodas larger than 16 ounces by restaurants, movie theaters, pushcarts and sports arenas.

The San Diego study tested the effects of limiting drink sizes on people’s soda consumption by offering them three different menus. One menu offered 16-, 24- or 32-ounce drinks; a second gave them the choices of a 16 oz. drink or bundles of two 12-ounce drinks. A third menu offered only individual 16 oz. drinks.

When the 100 students participating in the study chose from the menus as they would at a fast-food restaurant, they bought more soda from the menu with packs of 12 oz. drinks than they did when offered individual sodas of different sizes. Based on the choices, total business revenues were also 65 percent higher when menus included packs of drinks rather than only small-sized drinks.

“Our research shows the New York City ban on large-sized drinks may have unintended consequences,” said Wilson, a doctoral student in UCSD’s psychology department. “Sugary drinks are a major source of business revenue, and businesses will adjust their menus in order to maximize profits.”

Even nutritionists agree that legislating people’s soda consumption is a tricky business.

“I discourage anyone from drinking 32 ounces of soda, but the issue is: what can we legislate?” said Keith Ayoob, director of the nutrition clinic at the Children’s Evaluation and Rehabilitation Center at New York’s Albert Einstein College of Medicine. “Bloomberg’s intention was good, but people still want to have choices and the freedom to make wrong ones. It’s a sad commentary on our society that they want to legislate what people eat.”

Madelyn Fernstrom, TODAY diet and nutrition editor added that the San Diego study looked at purchasing rather than actual consumption.

“Limiting drink size can increase mindful eating - paying attention to what you’re buying,” she said. “I don't think this study represents a strong argument against limiting soda size in restaurants and chains. Besides, the fastest way to supersize would be to go down the block to a bodega or 7-11 where these rules don't apply.”

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