The New York mayor defends his prohibition on sugary drinks with an appeal to science, but the very people who carried out the studies in question say he's misread their work.Joshua Lott/Reuters
On June 1 -- National Donut Day -- New York City's mayor proposed a restaurant ban for any soft drink over 16-ounces. The hope is that by banning big drinks people will drink less and weigh less. He and others cited our research as the science behind the policy. Indeed, a dozen of our studies show when you randomly give people large sizes of food like popcorn and French fries, they overeat. Another of our cited studies showed that people ate 73 percent more soup when eating from a soup bowl that secretly refilled itself.
There's a critical difference between the lab and Lexington Avenue that the mayor's office didn't account for: when Joe the Plumber and Bob the Banker buy soft drinks, they buy the size they want. They aren't randomly forced to take a 44-ouncer when they really wanted a 12-ouncer. Moreover, their Coke or Pepsi doesn't magically refill itself. If that happened, they'd overdrink. Instead, most restaurants give us a choice of a small or large drink -- just as nearly every fast food outlet gives us a choice of small, medium, or large fries, and every movie theatre gives us a choice of small, medium, or large popcorn. People who want a little buy a little, and people who want a lot figure a way to get it.
Yes, we have found that when people are given larger portions, they do drink or eat substantially more. But to claim that these results imply that the ban will be effective is to ignore our larger body of work. In our experiments, subjects were given larger or smaller portions of food in a dining or party setting, where they were unlikely to notice portion size. It is exactly because participants weren't paying attention that we got the results we did.
The mayor's approach, however, overtly denies people portions they are used to be able to get whenever they want them. In similar lab settings, this kind of approach has inspired various forms of rebellion among study participants. For example, openly serving someone lowfat or reduced-calorie meals tends to lead to increased fat or calorie consumption over the whole day. People reason that because they were forced to be good for one meal, they can splurge on snacks and desserts at later meals.
We've dedicated our research careers to helping people eat better. Some of the ideas that have grown from our work and that we've actively promoted include contributing to Smarter School Lunchrooms, 100-calorie packs, and the 2010 Dietary Guidelines. In the interest of disclosure, we've never received money from soft drink companies, nor have we received money from the New York City Department of Health or Mayor Bloomberg's office to investigate a better solution. We fear, however, that the proposed ban will be a huge setback to fighting obesity for two reasons: 1) unless it succeeds, it will poison the water for better solutions, and 2) it won't succeed.
First, consider the McLean Effect: McDonald's launches the visible and controversial low-calorie hamburger; it fails, becoming a cautionary byword for restaurants for the next 15 years, when no one dared introduce low-calorie fast food offerings because "Look what happened to the McLean."
Banning larger sizes is a visible and controversial idea. If it fails, no one will trust that the next big -- and perhaps better -- idea will work, because "Look what happened in New York City." It poisons the water for ideas that may have more potential.
Second, 150 years of research in food economics tells us that people get what they want. Someone who buys a 32-ounce soft drink wants a 32-ounce soft drink. He or she will go to a place that offers fountain refills, or buy two. If the people who want them don't have much money, they might cut back on fruits or vegetables or a bit of their family meal budget.
Who buys large soft drinks? It's not just the people who may have some disregard for their weight. It may also be the construction worker who buys a single drink and nurses it all day. It may be the family of three who decides to split a single drink to save money. Soft drinks are bought by one-third of the poorest 2 million New Yorkers, but only one-sixth of the richest 1 million -- those who prefer to sip their fruit smoothies and lattes without regard for the burden on the less affluent soda drinkers.
Indeed, part of the fervor and support of a ban may be less about politics than personal preferences. One of our current studies shows that a person's belief about various food issues is driven more by their preferences than their politics. For instance, the more fast food you eat, the more unfavorably disposed you are to soft drink taxes, and the more favorably you view high fructose corn syrup. You have the exact opposite views the more you cook at home. In either case, it doesn't matter what your political party is, it's what you do that informs your opinion. But personal preferences is no way to decide policy. People wouldn't stand for a splinter group of vegetarians who campaigned for a ban on restaurant meat entrées over 8-oz, nor would they stand for the two of us -- as non-coffee drinkers -- crusading for a ban on the 20-oz Starbucks Café Mocha because it had 340 calories.
There is a better way to avoid being the McLean of Public Health. Soft drink companies and restaurants make money by selling beverages -- not sugar. By working with these companies, New York City could discover new ways to better promote lower-calorie options. While consumers deride brands, they love promotions. For instance, perhaps there could be a meal deal discount if a person bought a diet drink. Or a perhaps a healthy habit loyalty card would be given out and punched if a person opted for milk, juice, or water instead of a sugary drink. But the mayor's office has said that it does not want to work with retailers to brainstorm options for workable solutions. Retailers and manufacturers that are struggling in a recession would have welcomed a carrot instead of a stick.