Health Halos: A Class Experiment

I’m currently co-teaching an upper level university course on obesity with my Ph.D. supervisor, Dr. Diane Finegood, and recently gave a lecture exploring topics related to food consumption (the course is modeled around the clusters and variables of the Foresight Obesity System Map). It is hard to help others understand that the message to “eat less” really is a complex challenge and not the simple solution for weight loss. I hoped that by exploring the complexity of the food consumption cluster, students in the class would have a greater awareness of this.

One of the ideas I wanted to discuss in class was that of health halos – how labels and perceptions of a food or a meal being healthy may lead to unintended consequences. I’m trying to break away from the habit of traditional lectures, so used an experiment to help stimulate class discussion. I modeled the in-class experiment after one conducted by John Tierney and Dr. Pierre Chandon as described here. If students studying obesity, that have taken classes in nutrition, realize that even they can be fooled by health halos, it may lead to better understanding of the challenges faced by those who are trying to lose weight.

At the start of class, I handed each student a short questionaire. I prepared two versions. One version, given randomly to one half of the class, asked students to estimate the kilocalories provided by a meal of:

  • 3 cups of chicken penne in asiago sauce
  • 1 glass of wine

The second version, given to the other half of the class, asked students to estimate the kilocalories provided by the same dishes, but also including a greed salad:

  • 3 cups of chicken penne in asiago sauce
  • 2 cups of green salad with fat free salad dressing
  • 1 glass of wine

Both questionnaires also had images of each food listed on the questionnaire. Students were asked to write down the calorie estimation on the page and I collected of the papers to tally up the results. How did the addition of green salad to the meal affect students’ ability to estimate the energy value of the meal? Would students with a background in nutrition perceive the meal with salad to have less energy than the meal without the salad? Or would their knowledge of nutrition and obesity help them remain immune to the health halo?

Evidence from a series of experiments conducted by Pierre Chandon and Brian Wansink in 2007 suggests that if we believe a food to be healthy, we tend to underestimate its caloric content.(1) In their first experiment, Chandon and Wansink explored the perceptions people have about the healthfulness of meals served by Subway and McDonalds and how this affects estimations of the amount of energy provided by the meal. Study participants were recruited while dining at the restaurants, and asked if they would partake in a brief survey. Not surprisingly, participants rated meals from Subway as healthy while McDonald’s goers freely admitted to their not-so-healthy choices. The results showed that both Subway and McDonalds goers tended to underestimate the energy provided by the meals they ate. But does the perception that Subway is healthier skew this underestimation further? Alas, yes. The underestimation of the caloric value of meals by participants who dined at Subway was greater than those who dined at McDonalds. For a 1000 kilocalorie meal, participants believed it provided about 20% less energy if it was from Subway than if it came from McDonalds.

So what happened in class? Students given the meal of pasta and a glass of wine (without salad) estimated the meal to provide about 1640 kcal. This was a slight over-estimation (the actualy caloric content was about 1400 kcal for the meal). The other half of the class, given the meal of pasta, a glass of wine, with the additional green salad, estimated the meal to provide a mere 700 kcal – less than half of the actual caloric content and estimates of the same meal without salad. (The salad added only about 50 kcal to the meal.) Our results were no different than predicted from Chandon and Wansink’s study and mirror the results from John Tierney’s New York Park Slope survey.

We teach our course on obesity from a complex systems perspective, stretching students to move beyond the perception that weight loss is simply a matter of “eat less, move more”. One aspect of our approach is to help students recognize the complexity of the food environment. Participating in this experiment enabled students to recognize that even they are susceptible to health halos, despite having taking previous courses in nutrition. It’s often too easy to fall into the trap of “yes, that’s true for others, but not me, I’m immune”.

So how do we use this information about health halos to help develop solutions that will work within a complex system? Stay tuned for a future post where I’ll explore the solutions posed by students in a subsequent class.

1. Chandon, P., & Wansink, B. (2007). The Biasing Health Halos of Fast‐Food Restaurant Health Claims: Lower Calorie Estimates and Higher Side‐Dish Consumption Intentions Journal of Consumer Research, 34 (3), 301-314 DOI: 10.1086/519499

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One Response to Health Halos: A Class Experiment

  1. Courtney says:

    This is fascinating! I wasn’t familiar with the term “health halo” but am definitely familiar with the concept. I’m guessing that many food product labels (such as “low fat” or “natural”) cause people to underestimate calories as well. Thanks for your post. The blog is fascinating and I look forward to the next post!

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