By Aaron Carroll MD

There are times I wish I had a macro for the beginning of a post on obesity. Some way to say obesity is bad, obesity is prevalent, and nothing seems to work. You know the drill.

But there’s a new study in Health Affairs that was surprisingly promising:

We performed three related field experiments at a single fast-food restaurant to determine whether these reported sentiments could be translated into a strategy to alter calorie consumption. All of the experiments addressed three important elements of eating behavior.

First, do people spontaneously request smaller portions—that is, even if smaller portions are not specifically noted as an option on a menu or signage? Second, do people accept explicit spoken offers to take smaller portions in order to reduce calories? Third, does taking a smaller portion of one meal component lead to indulgence in other meal components, so that the calorie “savings” from downsizing are immediately lost?

Each experiment addressed an additional question. In experiment 1, we explored whether offering a nominal (twenty-five-cent) discount for downsizing would result in more customers’ accepting the offer than offering no discount. In experiment 2, we examined whether offering an opportunity to accept a smaller portion would be more effective than providing calorie labels in encouraging moderation. In experiment 3, we investigated whether downsizing appealed only to customers who would otherwise have thrown away uneaten food, thereby affecting calories ordered but not calories consumed.

Let’s start with experiment 1. First, they measured how many customers would spontaneously request a smaller portion of a high-calorie, high-starch side dish. Not surprisingly, only 1% did. But if customers were asked, on the other hand, one third accepted the offer, regardless of whether a discount was offered. What’s more, those that did downsize did not compensate by up-sizing any other portions of the meal. Those that downsized ordered significantly fewer calories, 100 fewer on average.

Experiment 2 compared menu labeling of calories (which I’ve discussed somewhat cynically a  number of times) with asking people to downsize. This is when it gets a bit crazy. First of all, significantly more customers accepted the offer to downsize their meal before calorie labeling was provided than after(21% versus 14%). In other words, menu labeling may have made them less likely to downsize. Additionally, in the group without menu labelling, when asked, those who downsized saved an average of 76 calories. With the menu labeling, they saved fewer (although not statistically significantly fewer) calories, only 17 on average. Not only did menu labeling not help; it may have made things worse.

Experiment 3 tried to tease apart the difference between what was ordered and what was eaten. It’s possible that people who didn’t downsize left more on their plates than those who did, meaning that ordering fewer calories didn’t lead to less calorie consumption. But those who rejected the offer to downsize (and therefore had more food to start) had no less left over than those who did downsize their orders. In other words, those who accepted the offer to downsize actually consumed fewer calories.

Granted, this is one study of Chinese fast food. I’m encouraged by the results, though. I’ve always acknowledged the tension between a need for better policy and the pushback against “nanny-state” solutions. But in this intervention, just asking people if they would like to eat less resulted in a decent number of people agreeing to. It worked better without menu labeling than with it. And it was entirely voluntary.

Asking people to supersize works. Apparently asking them to downsize does, too. We should try that more often.

Aaron E. Carroll, MD, MS is an associate professor of Pediatrics and the associate director of Children’s Health Services Research at Indiana University School of Medicine, as well as the director of the Center for Health Policy and Professionalism Research.  Carroll’s work has been featured in The New York Times, USA Today, The Los Angeles Times, Newsweek, and many other national publications. He blogs at TheIncidental Economist, where this post was originally published.