Small Cans of Soda? You May Not Drink Less

SMITH BRAIN TRUST — For years, soda servings have been ballooning. For its first half-century, Coke's main product was a 6.5 ounce bottle. Later came the reign of the 12-oz. can. In recent years, you couldn't get anything smaller than a 20-oz. behemoth-bottle from many vending machines.

A health-related backlash against sugary drinks has put the industry on the defensive, and one way soda companies are fighting back is by offering small portions. In the U.S., some of Coke's strongest sales have included "mini" cans and bottles ranging from 7.5 to 8.5 ounces, first introduced in 2007.

In the first five months of 2015, for example, Coke's retail sales of the small cans and bottles were up 17 percent, the company pointed out on its website — significantly outpacing sales of larger bottles. These new cans and bottles often have vintage design cues that may make them distinctive and desirable, but they're also designed to appeal to calorie-conscious consumers. And the strategy is working. "The consumer is very much approving the smaller packages," Coke's CEO told Wall Street analysts last summer.

You might think that, under this scenario, everyone wins. Consumer-goods companies often goose profits by selling goods in smaller packages, which raises the price per ounce. And, if you're going to drink soda, the 90 calories in a mini-can seems like a wiser call at lunch than the 240 calories in a 20-ounce bottle. (Those bottles contain 2.5 servings in theory, but when was the last time you stretched out a bottle for 2.5 lunches?)

Rebecca Ratner, marketing professor and assistant dean for academic affairs at the Robert H. Smith School of Business, points out that the psychology of portion size can be surprisingly nuanced. For some consumers, she says, "Smaller servings, including 100-calorie packages of cookies or mini soda cans, can backfire."

To be sure, much research has established that large packages and bigger restaurant portions lead people to eat more, as a general matter. (Indeed, more broadly, big packages prompt heavier use of many consumer products, even laundry detergent.)

But there's some evidence that "restrained" eaters, those worried about their waistlines, and "unrestrained eaters," those who eat more impulsively, react differently to portion sizes, Ratner says. One 2008 study, for example, published in the Journal of Consumer Research, found that unrestrained eaters responded to large and small snack packages much as you'd expect, scarfing down more treats when they came in larger bags. But restrained eaters react differently.

For one thing, they view small packages of high-calorie foods in part as "diet" foods, which leads them to let down their guard. Moreover, the mixed message of high-calorie goods in small packages — decadent snack! diet portion! — also puts restrained eaters in a state of agitation. And agitation can also lead to less self-control.

The authors of that Journal of Consumer Research study wrote that the finding that small packages lead restrained eaters to consumer more food "is another hurdle in the fight against obesity." So while those small cans might be cute, if you're diet-conscious you might want to view them with a wary eye.