Study: Traffic Light Food Labels Strengthen Self-Control

10 Mar 2015 --- The issue about whether food products should carry traffic light-style nutritional information symbols is an ongoing debate in many countries.

However, researchers now have more concrete evidence that the traffic light label is more effective in helping consumers resist high-calorie foods than a purely information-based label. In a study published in the journal Obesity, scientists from the University of Bonn observed participants in the brain scanner as they made purchase decisions. 

“This is the first study that analyzes the effect that traffic light signals have on the evaluation processes in the consumer's brain when making a purchase decision,” says Professor Dr Bernd Weber of the Center for Economics and Neuroscience (CENs) at the University of Bonn. 

The traffic light system on food products is designed to be easy to understand, for example ‘red’ symbolises a high percentage of fat, sugar or salt, while ‘green’ shows a lower percentage. 

Traffic light labelling: the UK

In the UK the Department of Health rolled out a front-of-pack traffic light labelling system over a year ago, despite some resistance from suppliers. The UK scheme combines the traffic light system with Reference Intakes, which replace GDAs (Guideline Daily Allowances). 

The UK’s supermarkets had already committed to the labelling scheme before the national launch, while major food manufacturers such as Mars UK, PepsiCo and Premier Foods had also shown support for the scheme. 

In the run up to the launch of the UK scheme, Robin Hewings, Diabetes UK’s head of policy, said the system would help to reduce the number of people who were overweight or obese. 

One of the benefits of the scheme is that it encouraged food producers to work hard at reducing areas of concern, such as trans-fats and salts, in order to present the best labelling guide possible. Premier Foods, for example, made a pledge to reduce calories by one third across its full portfolio over the course of a year. 

Research in the UK by consumer group Which? Indicated that the traffic light style of labelling scheme worked best for consumers, but there have also been concerns that shoppers may be misinterpreting the labels. 

Study: University of Bonn

In the latest study by the University of Bonn, a total of 35 adult study participants, 19 of which were women, participated in the study at the Life & Brain Center in Bonn. 100 products and their nutritional information were shown to the participants lying in the brain scanner – from chocolate to yogurt to ready-to-serve meals. 

The participants were shown this information either in the form of currently used nutrition labels with grams and percentages per portion, or in the form of traffic light labels. Then participants had to indicate how much they were willing to pay for a particular product.

The participants were willing to pay significantly more money for the same product when the traffic light label was "green" compared to an information-based label. However, if the label was "red", the willingness to pay decreased more compared to the conventional information. 

"You can conclude that the traffic light label acts as a reinforcer: The health relevance of the ingredients is weighed more heavily into purchasing decisions compared to simple nutrition information", says first author Laura Enax of CENs.

Two brain regions affect the reward system

While study participants were thinking about what price they wanted to pay for a particular product, the scientists recorded the activity of various brain regions using functional magnetic resonance imaging. A red traffic light label activated a structure in the left inferior frontal gyrus, which has been repeatedly shown to be important for self-control. 

Activity in this region influenced the ventromedial prefrontal cortex, a region that “calculates” the subjective value of a product via the reward system, leading to decreased willingness to pay for unhealthy products.

The traffic light label appears to enable the study participants to better resist unhealthy foods compared to a label containing the traditional information on grams and percentages of the particular ingredients. A traffic light label probably implicitly increases the weight consumers place on healthiness in their decision,” says Prof. Weber, summarizing the result. The scientists at the University of Bonn now want to examine more closely how different types of food labels can be used to support consumers in their decision-making.