Really? Restaurant Calorie Counts Fight Obesity?

A new analysis of self-reported BMI data has advocates for restaurant calorie counts cheering that they really do fight obesity. In a fabulous illustration of how smart people can rationalize whatever they want to believe, Harvard professor Cass Sunstein is unequivocal about the success of adding calorie counts to restaurant menus:

All in all, it’s a terrific story. The people who need to lose weight are losing weight, and the people who are least likely to know about caloric content are learning about it.

Unfortunately, his storytelling is better than his critical thinking in this case. He’s basing his optimistic assessment of calorie counts on a paper by Partha Deb and Carmen Vargas that hasn’t been peer reviewed and relies upon self-reported BMI as its primary input for obesity trends. Self-reported height and weight have long been known to be unreliable. People report being taller and lighter than they actually are. And importantly for this sort of analysis, people in different communities have been shown to misreport their height and weight to different degrees, making comparisons across different communities unreliable.

Using self-reported height and weight means that the study — at best — proves people are reporting a lower BMI in communities that have calorie counts on restaurant menus. It’s entirely possible that people in those communities merely feel more social pressure to report lower body weights.

Although the analysis methods for this paper are reasonably rigorous, they do not adjust for other policy changes that happened during the study in these communities. So, as with any observational study, it remains possible that the changes observed were due to something other than restaurant calorie counts.

As Sunstein concedes in his commentary, considerable evidence prior to this analysis suggests that requiring restaurant calorie counts “just doesn’t succeed in promoting healthy food choices and reducing obesity.” Reflecting on how this latest study adds to what is known, Professor Greg Pavela of the University of Alabama at Birmingham summed up the current state of the evidence:

There may be other justifiable reasons to require nutrition labeling in restaurants, but justifications based on a purported effect of labeling on weight lack a firm evidence base.

At the end of the day, we like having calorie counts available on restaurant menus. But claiming that it has a significant effect on obesity is the product of wishful thinking, not science.

Click here for Sunstein’s commentary and here for the paper by Deb and Vargas.

Choosing from the Menu, photograph by Henry Burrows, licensed under CC BY-SA 2.0

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February 29, 2016