Reflecting on the Menu

Difficulty Reading the Menu (Data)

ObesityWeek 2014 BostonWe’re having difficulty reading the menu labeling data at ObesityWeek 2014. A study presented in the second annual Obesity journal symposium showed a promising result: a 50% reduction in weight gain over a 36-week academic year when college students were exposed to menu calorie labeling. The lead researcher on this study, Charoula Konstantia Nikolaou, says:

Calorie labeling helps people understand what’s in their food, and makes them aware of healthier options. Previous literature has shown little or no benefit from calorie labeling, however that research did not look at long-term exposure, and in those studies most consumers did not notice the calorie labels. We were glad to see that exposure to our very prominent calorie labeling for an entire school year did not just reduce weight gain in these students, but eliminated it altogether for the group. This is especially important because young adults are vulnerable to weight gain, which often leads to obesity later in life.

The efficacy of menu labeling has been a thorny issue for many scientists studying interventions to prevent obesity. So the news of a 50% reduction in risk was impressive and attracted a lot of attention. Everybody wants to believe in the power of information to help people make better choices and achieve healthier outcomes. But real proof that it works with menu labeling has been elusive.

This study has a lot going for it. It measures the effects over a longer time than prior studies — 36 weeks. Weight is the primary outcome, not a surrogate like purchases. But (you knew this was coming), it has a big problem. There’s not really a control group. The study employs a “pragmatic interrupted time-series study design.” They compare students in a university residence hall who eat in a dining hall in one year to students who live and eat in that same hall the next year.

Because of this design, bias can creep into the results in several ways: selection bias through a low participation rate, maturation bias, and self-report bias. In the words of the authors, “Practical constraints in a real-life setting forced a study design which cannot claim absolute proof.”

It’s great to have this data, unless it’s misused to serve as a substitute for what’s needed next — a real experiment with a robust design to prove that menu labeling can prevent weight gain (or not). Until then, all we have is a supposition that it might.

Click here to read the study, here to read more about threats to the validity of such studies, and here to read a study of the differences from year to year in the weight gain of college students.

Reflecting on the Menu, photograph © Glenn Loos-Austin / flickr

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