Restricting larger-sized soft drinks may lift consumption, study finds

Posted by AFN Staff Writers on 17th April 2013

Limiting the sale of soft drinks to small sizes could actually increase consumption, rather than decrease it, says a new US study published on 10 April 2013 open-access academic research site PLOS ONE.

The researchers from the University of California found that participants in a behavioural test study consumed significantly more soft drink when they were able to buy it in bundles of two servings.

The study’s authors, Brent M. Wilson, Stephanie Stolarz-Fantino and Edmund Fantino, said that the New York City ‘soda ban’, which the City Council attempted to impose earlier this year, would not have prevented larger-sized drinks being sold in this way as bundles of smaller-sized drinks.

“Prior research has shown that package size only influences use when different sizes have different unit costs,” said the study’s authors. “If the price per ounce of soda does not change between the varying conditions, soda consumption may not decline when bundles are offered in lieu of larger cup sizes,” they said.

The study had one hundred undergraduate students from the University of California participate in a behavioural simulation where they were offered varying food and drink menus. One ‘unregulated’ menu offered 16 ounce, 24 ounce, or 32 ounce drinks for sale. A second ‘bundled’ menu offered 16 ounce drinks, a bundle of two 12 ounce drinks, or a bundle of two 16 ounce drinks. A third ‘restricted’ menu offered only 16 ounce drinks for sale. The instructions for participants did not mention a limit on drink size, and they were not asked how they would respond to such a restriction. Menu prices were based on McDonald’s drink prices at the time of the study.

More soft drink consumed with ‘bundled’ menu

Participants bought significantly more ounces of soft drink from the ‘bundled’ menu than from the ‘unregulated’ menu, according to a test comparing the two groups. Participants did, however, buy significantly fewer ounces of soft drink from the ‘restricted’ menu than from the ‘unregulated’ menu when those two groups were compared.

Revenue greater with ‘bundled’ menu

The researchers also found that revenue from drink sales was significantly higher for the ‘bundled’ menu than for the ‘unregulated’ menu, when those two groups were compared. Revenue was also significantly higher for the ‘bundled’ menu than for the ‘restricted’ menu when those two groups were compared. The study’s authors suggested these differences in revenue would likely provide strong incentive for businesses to implement a ‘bundled’ menu.

Considerations for future policy

The study’s authors admitted that ‘bundled’ menus may also encourage people to share drinks, and that in a real life situation factors like the inconvenience of carrying multiple cups could affect purchasing decisions. “However, this research shows a potential unintended consequence that may need to be considered in future policy making,” said the researchers.

Australian Food News reported in March 2013 that a New York Supreme Court judge ordered an injunction against the ‘soda ban’ just before it was due to be imposed. At the time, New York City Mayor Michael Bloomberg said the City would appeal the decision.