A team of US scientists have discovered that including the calories with pictures of food, for example, on a menu, can help people make healthier food choices. The scientists used a MRI scanner to detect brain reactions to the pictures to enable them to understand what effect this could have. The article was published in PLOS ONE and is an open access study which can be read in full online.
The scientists’ starting point was that although calorie-labelling of food is increasing, there was no evidence that confirmed that it had any influence on consumers. About one third of consumers say that they use calorie information to make food choices, and they have been found to over-report their use of nutrition labels: they may intend to, but they may not. When food nutrition information is paired with additional information such as exercise equivalents or symbolic heath icons, then it has been shown to be more effective. Females and dieters may also be more likely to use food nutrition labels when making decisions about food than males and non-dieters.
Food cues activate the brain in reward regions such as the nucleus accumbent and orbitofrontal cortex, which motivate consumption. People can react differently to food because of past experiences or a present situation, eg: weight status, momentary food cravings, giving in to food cravings or post-surgery weight loss. These different reactions can affect the brain’s response to desired food. If information on calories is not available, then people make food decisions based on how tasty they think the food will be and whether it is something they want to eat. Dieters will have a different understanding when calorie information is not present as they may represent foods differently, according to the perceived healthiness of a food.
42 participants were recruited, aged between 18-22 for the study. They were classified as either dieters or non-dieters according to the Revised Restraint scale. Their weight, BMI and percentage of body fat were noted, and were mostly within the normal weight range. Two were classified as obese. The scientists chose 180 food images, eg: a cheeseburger or a slice of cherry cheesecake, sized to be the same with backgrounds changed to white. Each food image was either given an arbitrary number or the number of calories below the food image. The images were all displayed twice: once with the calorie information and once with the number. The participants were asked to score each picture of food depending on how much they would like to eat it: 1 being not at all and 4 being very much.The non-calorie labelled food pictures were presented first so that the scientists were able to understand the food preferences of the participants. Then the food with the calorie labelling. Finally, the participants were told that the calorie labelling might not have been correct, so should be disregarded and they were then asked to estimate how many calories in each food. While viewing the first two sets of images and evaluating their desire to eat the food, the participants were inside a fMRI scanner to enable the scientists to see which region of the brain was responding to the images.
Both dieters and non-dieters rated food that had been calorie labelled as less appetising, but the effect was strongest in dieters. They also demonstrated similar brain activation for the food which was not labelled which suggested that dieters may think about calorie information, even when food is not labelled. If people are following health cues, then they may be more open to using past experiences or knowledge to help them make healthier food decisions.
The orbitofrontal cortex has been found to show activation to both food cues and alcohol cues, and this was the part of the brain that showed differing responses to the food images. The scientists suggested that their work could be used to examine the responses of smokers when graphic images are used on packaging. The scientists pointed out that the motivation has to match the desire in order to change behaviour, and that the images on smoking packaging may be more likely to influence light smokers rather than heavy smokers. This study did not examine long-term results - effects of systems such as nutritional labelling can lose the effect as people grow accustomed to its use. The scientists suggest that multi-step change may be the most effective way to change people’s behaviour when it comes to food choices: that while health-related information on food can help people to understand the effects of the food they consume, that increased public education on the importance of thinking about the calories of the food we eat might also be effective at encouraging people to make wise choices.
Courtney, A.L., et al., Calorie information and dieting status modulate reward and control activation during the evaluation of food images, PLOS ONE, 2018; 13 (11): e0204744